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  • Rapt in Awe

    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Events for March 2014: Planet Sandwich Seasoned with a Sprinkling of Zodiacal Dust

Two realities - The image above gives you an idea of the true size and look of the planets visible in March skies. (From left, Venus, Earth, Mars, Jupiter, Saturn) That's one reality. What you see with your naked eye looks like stars - though very bright ones.

Two realities – The image above gives you an idea of the true size and look of the planets visible in March skies. (From left, Venus, Earth, Mars, Jupiter, Saturn) That’s one reality. What you see with your naked eye is much different.  Planets look like stars – though very bright ones  and some with distinctive hues.

At dusk Jupiter dominates the night sky high overhead –  think of it as one slice of bread for our sandwich. During morning twilight Venus dominates the sky low in the east – that’s the other slice. Between we have Mars on the evening side of midnight and Saturn on the morning side of midnight.

The “seasoning” – Zodiacal Light  – is interplanetary dust that forms a soft cone of light rising out of the west about 80 minutes after sunset – but is only visible if your skies are dark enough.

In total this makes a tasty show at any time of night to supplement the annual,  ever-advancing march of the stars. Here’s where and when to look.

The Zodiacal Light is the most challenging and can’t compete with the Moon’s light, so it’s available for the first two nights of the month, then comes into view again starting on the 18th and going for the rest of March, 2014.  To see it you need a clear sky to the west with no light pollution in that direction. You also need to allow your eyes to dark adapt. for 20 minutes. What you’re looking for is something roughly akin to the Milky Way in brightness, but in a soft pyramid shape that starts out wide as it rises from the horizon and leans to the south as it reaches one-third or more up the sky in the general direction of Jupiter. It’s really quite an amazing feature.

If you see it, reflect on this explanation from Wikipedia:

The material producing the zodiacal light is located in a lens-shaped volume of space centered on the Sun and extending well out beyond the orbit of Earth. This material is known as the interplanetary dust cloud. Since most of the material is located near the plane of the Solar System, the zodiacal light is seen along the ecliptic. The amount of material needed to produce the observed zodiacal light is amazingly small. If it were in the form of 1 mm particles, each with the same albedo (reflecting power) as Earth’s Moon, each particle would be 8 km from its neighbors.

For the metrically-challenged (that includes me) that means one dust particle every five miles! In the light of that information, it’s absolutely awesome if you see any thing at all!

Jupiter dominates the stars of Gemini, including the two bright twins to the left, Castor and Pollux.  In the midst of the brightest stars in our skies - the Winter Hexagon - it is the brightest of them all.

Highly recommended that you click this image for larger version. Hard to see the stars otherwise.

Jupiter  is on top these March nights, sharing the same general area of sky as the Gemini Twins. I took the picture (above) of it in late February – it’s position in March won’t change much, though it will get a little dimmer, it will still be much brighter than any star. As always, it’s fun to see if you can hold your binoculars steady enough to detect one of its four largest Moons. When it’s high like this you’re looking through less air and they may be easier to spot – but then, it’s a  bit hard on the neck to look so high in the sky while holding binoculars.

Again. to see any of Jupiter’s Moons your eyes have to be dark adapted, its best to use the largest, most powerful binoculars you can hold, such as 10X50, and you need an idea what to expect. The moons will be roughly in line with Jupiter’s equator – but at any given moment the number visible will vary, as will their distance from the planet, and which side they may be on. (They can all be on one side, they can be split two to a side, etc.) Jupiter together with its Moon – even when they are most distant, are only going to take up about 1/20th of the typical binocular field.

Here’s the sort of thing you are hoping to see:

How Jupiter’s moon might appear at one specific moment – in this case a moment when they were all on the same side of the planet. Of course the next night the view could be quite different. The letters stand for Europa, Io, Ganymede, and Callisto.

If this is your first time looking for the moons, do yourself a favor. Go to this page at the Sky and Telescope Web site and open the JavaScipt utility. It will tell you right where the moons are – and which is which – for any given moment.

As Jupiter dims a bit during the month, Mars becomes quite bright reaching magnitude -1.3 by the end of the month, and shines with a distinctive reddish hue. That’s  almost as bright as Sirius, but is no challenge to Jupiter, both of which appear white.

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

It rises about 3.5 hours after Sunset at the start of the month, but comes up during evening twilight at the end of the month. Generally it will be well placed for naked eye observing about an hour after it rises – those with small telescopes may want to wait another hour or two for a better view. That’s why I see it primarily as a late evening object.

You’ll find it by looking to the east about four hours after sunset as March begins. The Big Dipper will be high in the northeast. Follow the curve of it’s handle down to the bright star Arcturus. Continue this curve and you will come to Mars, roughly five degrees from the bright blue star, Spica. (Remember: When low on the horizon bright stars and planets will appear to sparkle and change color because you are looking through so much air.) While these relationships will remain the same, as the month goes on Mars will be rising earlier and earlier.

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

Saturn still is best seen in the early morning hours, though it rises just before midnight in the southeast. I think the best guide to it is the triangle it forms with Arcturus and Mars. Of the three corners of this triangle, Saturn is dimmest, shining with a soft yellowish light. However, it still outshines the stars in its vicinity.

You can’t miss Venus if you’re up an hour before sunrise. It actually comes up a couple hours before sunrise and in morning twilight is well above the southeast horizon an hour before sunrise. At about magnitude -4.7 (it gets a bit dimmer towards the end of March) it simply outshines everything except the Sun and Moon, so there’s no mistaking it and no difficulty finding it. Just look in the right general direction at the right time.

On March 27, 2014 a very thin, waning crescent Moon should fit in the same binocular field with Venus roughly three degrees up and to the left.

Events December 2012: Mercury, Meteor Shower, Dwarf Planet, Jupiter, and more!

geminids

OK, so the meteor shower might be a snow shower, it being December and all, but we also get  an especially nice apparition of Mercury with Saturn and Venus guiding us to the elusive planet. And if that’s not enough, we have the ever reliable Winter Solstice – start beating the drums to bring the Sun back out way, please – and the King himself, Jupiter dominating an already brilliant eastern evening sky  plus a nice asteroid pass to accompany a not-quite-as-bright Dwarf Planet – you know, one of those Pluto-like things! Whew – out of breath just thinking about it all.

Here are the links to one  event at a time if you want to jump straight to the details.

Geminid Meteor Spectacular – December 13-14

First, please meditate on this: Ask someone who is 50 miles away to strike a wooden kitchen match. Can you see it? Of course not. But that’s what’s going on when you see a meteor flash across the sky! Chances are it is from a particle about the size of the head of a kitchen match – or smaller –  and it is burning up as it hits the atmosphere above you travelling at up to 100 times faster than a rifle bullet.The result? A very, very bright “match.”

And now the Geminids – As you may know, I really don’t like that word “shower.” It builds expectations out of proportion usually, but if you have clear skies on the night of December 13-14th it’s worth digging that folding  chaise lounge out of storage, wrapping yourself in a sleeping bag – with binoculars and hot beverage handy – and staring up at those wonderful bright stars of winter waiting for some to “fall.”  Hey, if you have an Iphone or Ipad there’s an app for this – no kidding – you can record what you see and ship it off to NASA, thus contributing to scientific research –  all quite painlessly. (Go here for details.)

Oh – and this is the time of new Moon, so the Moon won’t be present to upstage the show with its bright light. The official word goes something like this – expect “about 120 meteors visible per hour for an observer at a dark sky site late on the peak night.”  That’s how Sky and Telescope puts it and those folks certainly know what they’re talking about, but in many nights of meteor watching I’ve never seen anything close to 120 per hour. When that’s the forecast I figure I have a good chance of seeing 20-30 an hour and believe me, that’s a real treat.  Maybe your skies are darker than mine, maybe your eyes are better, and maybe you’re more patient – so maybe you’ll see 120. Me – I will be delighted with a meteor every two-to-three minutes –  if not a quite a shower, that’s a  snappy snow flurry!

So where do you want to look? Up! Any part of the sky  can produce meteors, but if you trace their trails backward you will see they all emerge from the same general section of sky near Castor, the slightly dimmer Gemini twin.  Since they appear to radiate from this area of sky the most meteors will be visible when it is high overhead – and looking in that general direction is a good idea. Here’s a chart for 1:46 am ET -when Castor is at its highest – on the morning of December 14.

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

So does that mean you have to wait until  early morning to enjoy the Geminids? No! But it makes sense that if the radian point is near the eastern horizon – which it is a couple hours after sunset – then you cut your chances of seeing a meteor in half – which still means a very respectable number of meteors.  The higher the radiant point the more chance you have of seeing more meteors. But then, you can’t watch the whole sky at once – even if you have remarkably clear horizons – and one thing about meteors – they are very fast and there’s no instant replay. Blink – or be looking the wrong way – and you may hear the ooohhs and aaaahhs of companions, but you will most likely not see what they saw.

Most meteor showers are the result of the Earth passing through a trail of comet dust  – think of “Pigpen” in “Peanuts” and you get the idea of comets leaving a trail of dust. But not the Geminids. They’re something of a mystery, but the current theory is that they come from a maverick asteroid. To read all about it, go here.

Hey – why not do the observing right?  Go out about 2 am and enjoy a couple hours of meteor watching, then shift your focus to the eastern horizon where Saturnn, Venus, and eventually Mercury will put in an appearance – quite a show, really.

Mercury – an early month, early morning stage appearance with Saturn and Venus

Mercury  reaches longest elongation – distance from the Sun –  on December 4th and while it will be well-placed for another couple weeks, you need to grab the little winged messenger when you can. It pops above the horizon six times a year – three in the morning sky and three in the evening sky, but not all pops are created equal. This happens to be its best appearance for 2012.  As a bonus, brilliant Venus will act as a guide. The two planets will be closest on December 9th when you should be able to squeeze them both into the same low-power binocular field of view. But all month they will be close enough for Venus to help in finding Mercury and Saturn will be visible a bit above Venus.

Of the three, Venus will absolutely dominate in brightness at magnitude -3.9. But Mercury on December 4th will be just a tad dimmer than the brightest star we can see (roughly -0.5) and Saturn is no slouch at 0.65 – and they’re in the southeast with two bright guidepost stars, Arcturus and Spica. Here’s what to expect.

Click image for larger version. (Prepared from Starry Nights Pro screen shot.)

December 11th isn’t so shabby either because we get a crescent Moon in the picture as well, though both Venus and Mercury have dropped  down a bit, you should still be able to find them both. Venus will be easy. Mercury – well, you may want to use binoculars, though it should still be visible to the naked eye if you have clear skies – and, of course, an unobstructed eastern horizon. It’s only about half a fist above the horizon at this point.

Click image for larger version. (Created from Starry Nights Pro screen shot.)

The Winter Solstice – Sure it happens every year but it always seems special – December 21

What’s so special about the Winter Solstice? Well, for me it’s a reminder that all life – you and I, plus every animal and plant on this tiny planet depend on the Sun. The Winter Solstice – as seen from the Northern Hemisphere –  reminds me of this because on the morning of December 21 the Sun will rise as far south as it gets. In the next few days it will start inching it’s way back north and that is certainly a good sign. Sure, our seasons lag behind the sky a bit. The worst of the winter weather is yet to come. But the fact that the Sun is on its way back is certainly an encouraging sign. More primitive societies that were in better sync with the natural rhythms of the sky, celebrated this time of year and with darned good reason.

Ceres is Ceres – but you can call it a dwarf planet

“Dwarf planet” was the category astronomers agreed upon in 2006 to fit objects that are big enough to be round, but too small to have cleared the area of their orbit of other objects. That’s what Ceres is and so is Pluto, and three other known objects.  It amazed me that this rather technical decision (I have greatly over-simplified the definition) caused such a stir because it demoted Pluto from planet to dwarf planet. These are simply classifications and in astronomy over time classifications get kind of messy. I mean, stars in the 19th Century  were classified in a nice alphabetical list by their spectra – but then we kept learning more and the list got screwed around  to anything but alphabetical: OBAFGKMLT. What’s more, our Sun – and many other stars that are among the larger ones, is called a “dwarf star!” Oh my – now that sounds illogical, if not offensive.

Oh – and Ceres, the first asteroid discovered (1802) – and largest (952km) – is still often referred to as an “asteroid” because it is a dwarf planet inside the orbit of Neptune where we usually find asteroids – arghhhhhhh! See why I want to just call it Ceres and be done with the naming thing ?  😉

Do click onthis for the full-size image - that's really Vesta as imaged by Dawn, but essentially this is an artists view of what it must have looked like as the Spacecraft orbited the asteroid.

Do click on this for the full-size image – that’s really Vesta as imaged by Dawn, but essentially this is an artists view of what it must have looked like as the Spacecraft orbited the asteroid.  (We didn’t send anyone along in another spaceship to take pictures of the two!)

But Ceres – and even brighter Vesta – have been the subject of an extensive examination conducted by the NASA  “Dawn” spacecraft.  It has spent a year examining Vesta and is now on its was to get up close and personal with Ceres. But you can beta it to it – you can see both Cere and Vesta from your backyard this month with nothing more than binoculars, a few charts, and some determination. Of course your view will be a bit less detailed. The two will appear as stars just below naked-eye visibility. And although it’s about half the size, Vesta is the brightest because it happens to be made of – or have on it’s surface – shinier material.

This is an excellent opportunity for you to test your skill with binoculars. This month they will both look like sixth magnitude stars and thus be easily seen in binoculars – but I won’t underestimate the challenge. The good news is they are well placed near bright, familiar stars and the brilliant planet Jupiter in the evening eastern sky. That makes it easy to find the general area in which to search. The bad news is there are lots of stars up there – especially when you look with binoculars – so you need to really study the charts before you go outside, then do  very careful observing. If you find it one night, it’s  fun to look again in a few days, or even a week or two – because they do change positions rather rapidly while the stars, of course, stay put.

Go here to get a printable chart of the Path of Ceres and Vesta over the next few months.

Now print this chart to use to mark your observations of Ceres and Vesta over the same period.  It’s a chart of the same area of sky covered by the previous chart, but with the position of Ceres and Vesta shown only for December 9, 2012 as viewed from mid-northern latitudes about four hours after sunset. However, while the orientation changes somewhat by date and time, it should serve to track Ceres and Vesta for December and January. Magnitudes of a few selected objects are given in parenthesis to help identify Ceres and Vesta. Before going outside to make your observation, study the chart and determine where you think Ceres and Vesta should be that night.

And as you look at Vesta, get this picture in your mind’s eye – and as you will see at the end, Ceres look a bit different, but how different – well, we’ll see when Dawn gets there!

And here’s the best view we have of Ceres as seen by the Hubble Space Telescope.

Images of the Asteroid Ceres As It Rotates One Quarter
Source: Hubblesite.org

Jupiter – let’s not forget the king of the planets

As some wag commented, our Solar Systems consist of the Sun, Jupiter, and some debris!

It is big – and only Venus outshines it, and yes, with careful viewing you can see one or more of the four Galilean moons using only binoculars. The key is to hold them steady and observe – don’t just look.  A “look” is what most people tend to do at first – that is, they hold the binoculars up and if, in 10 seconds or so, they have not seen the moons, they give up. That is not observing. To observe you need to look for at least a solid minute. That won’t guarantee you see the moons, but just taking a quick look can mean you easily miss them.

They may all be on one side of the planet and they constantly change their relationship with the planet and one another so that even with binoculars you can notice the difference over the course of a few hours. They will look like tiny stars, they will be close to the planet, and they will be roughly in a straight line that passes through the planet’s equator. This line will be pointing upward as the planet rises, level off when it’s near the mid-point of its arc across the sky, and be slanting down as it heads for the western hprizon.

The best way to prepare yourself for what to see – to check to see if you are seeing the right thing – is to go to the Sky and Telescope web site and use the javascript simulator there for your date and hour.  To do that, go here . With binoculars you want the right-side up view. With small telescopes it is much easier, of course, to see these Moons, but a telescope will change the orientation and this script allows you to change that orientation to match your telescope’s view. Here’s a typical example of what you will see.

Events October 2011: Mars stirs up the Beehive, plus a little LunaSee Jupiter style!

October starts in September – at least when it comes to observing Mars this year! In fact, October 2011 will be a neat month for planet watching with naked eye and binoculars, not to mention a good time to catch the  Zodaical Light, as well as a few Orionid meteors  – and with the first items it’s good to get an early start. By early, I mean you can start your Mars watching near the end of September and this is an early morning event.  But if early morning isn’t your thing, take heart – King Jupiter and his retinue are available evening and morning. (Jump to here if you’re interested primarily in Jupiter.)

Fast-moving Mars

That said, let’s start with Mars because it has been fun to watch in September as it cruised through Gemini and for a brief period made the heavenly twins look like triplets. In October it’s even cooler as it goes ripping through one of the best binocular star clusters – M44, the “Beehive,”  known to the ancients as “Praesepe.” That last name is Latin for “manger” and some saw this as a manger, apparently with hay in it and two donkeys – the Northern Ass and the Southern Ass, eating out of it.

These are handy, relatively bright stars that Mars will pass between. They also  may help you with your Latin, for their more formal names are Asellus Borealis and Asellus Australis.  Seeing them in binoculars may help you pick up  the Beehive if  your light pollution is so bad that you are having trouble finding it, though binoculars certainly should bring it out in all but the worst conditions. Here’s the scene in the eastern sky early in the month a couple hours before sunrise.

Click image for a larger version. This is the view looking east about two hours before sunrise on October 1 when Mars will be about 30 degrees above the horizon - that's three fists. It will be about halfway between Castor and Pollux in brightness and should have a red tint very similar to Betelgeuse in Orion. (Chart prepared from Starry nights Pro screenshot.)

You can download a printer friendly version of the above chart to use under the stars here.

Here’s what typical binoculars – with a 7-degree field of view will show when you zoom in on Mars on October 1, 2011.

The view through binoculars. Click image for a larger version. Mars will be much brighter - and redder - than the stars in the same field. The brightest stars will be Asellus Borealis and Asellus Australis and they are about the brightness of the stars in the handle of the Little Dipper, so will not be seen with the naked eye unless you have skies relatively free of light pollution. (Prepared from Starry Nights Pro screenshot.)

This  cluster has been known since ancient times since it is visible to the naked eye as a dim cloud (if your skies are dark and your eyes dark adapted) – Galileo was able to resolve it into about 40 stars with his small telescope and you should be able to do the same with ordinary binoculars. There are actually more than 200 stars in this cluster and according to the Hipparcos satellite, the cluster is 577 light years away.

This also makes a handy illustration of sky directions. Remember – in the sky directions are a bit  different from on the ground – west is the direction the stars appear to move each night and north is the direction towards the North Star.  In looking at the Beehive you will get a good sense of North and South because Asellus Borealis and Asellus Australis line up pretty much north/south as their names imply. What’s more,   Mars is moving eastward against the background of stars and it’s travel can be seen from night to night. It will take it little more than a week to pass in and out of our binocular field of view that is centered on the Beehive and by early November it will be close to Regulus, the bright star at the base of the Sickle of Leo.

Eastward journey of Mars from September 25 to October 3, 2011. Circle represents the typical field of view for low-powered binoculars. Click image for larger version. Prepared from Starry Nights Pro screenshot.

Jupiter – evening, midnight, or morning – take your pick!

And I should add, bring your binoculars, for using them to spot Jupiter’s moons will be the real focus of this post.

Jupiter is a magnificent, brilliant “star” that rises in the east shortly after sunset and will be dominant on any night this fall – nothing will outshine it but the Moon – and as we get closer to winter, Venus. In early October you’ll have to wait until about three hours after sunset for Jupiter to be well placed for viewing. By the end of the month it will be high enough in about two hours after sunset. Once up, it’s good for the rest of the night, so if you’re out viewing Mars in the early morning, for example, take in Jupiter as well.  But the fun increases expoentially when you observe Jupiter with binoculars, or any  small telescope. We’ll focus here on the binocular view because most people have binoculars.

Why are binoculars so important? Because of Jupiter’s four bright moons which constantly change positions with the changes noticeable over a matter of hours and certainly from night-to-night. These are the Galilean Moons – the ones the great scientist discovered in 1610 and with nothing more than binoculars you can follow in his footsteps, discovering them for yourself. And try to imagine the excitement it caused, for discovering these Moons helped change our whole view of the universe – they were solid evidence that not everything revolved around the Earth, as thought, for here were four objects obviously revolving around another planet.

Jupiter can be great fun – and a challenge – for anyone with binoculars.  It is common to say that bincoulars are all you need to see Jupiter’s four bright moons.  This is true  – but I’m afraid a bit misleading.  Don’t think you’re going to just pop out the door some night in October and glance up at Jupiter with the binoculars you bought for sports events and immediately see the moons. Those binoculars should do the trick, but it’s a bit more challenging than that for most of us. (OK, I’m 70 years old and in average health with reasonable eyesight – someone younger, healthier,and with sharper sight might find this easier.)

For example, one recent morning I was surprised by a few hours of clear skies. I grabbed three pair of binoculars and decided to put this idea of seeing Jupiter’s moons to a systematic test. I’d glimpsed them before with binocuars, but most of the time I look at Jupiter either with my naked eye, or a telescope.  With the naked eye you can’t see the moons – with a telescope you can’t miss them. So here’s what I learned in my little binocular test.

With binoculars in astronomy the goal is to gather more light and the bigger the objective, the more light it gathers and thus makes fainter objects brighter. The 40mm objectives are roughly the equivalent of 63 eyes, the 56mm objectives, 123 eyes, and 70mm objectives 192 eyes.

First, my equipment included an ordinary pair of birding/sports binoculars – 8X40 Celestrons – I had bought several years ago.  I also had a pair of my favorite “quick look” astromical binoculars, the very large 15X70 Celestrons, and a pair I had recently bought from Garrett Optical as an experimental compromise to these huge ones – 11X56 Gemini binoculars. The issues here are simple. The larger the objective glass, the more light is gathered and thus the brighter the moons should appear.  The objective glasses on my binoculars were 40mm (quite typical), 56mm (unusual) and 70mm (pretty common as inexpensive astronomical binoculars go.) The magnification rose in keeping with the objective lens size – 8X, 11X, and 15X – and the more magnification, the more separation between moon and bright planet, so the easier to see the moons.

Bigger objectives means bigger - and heavier - binoculars. From left, these are 15X70, 11X56, and 8X40.

This should quite obviously point to the 15X70s being the binoculars easiest to see Jupiter’s moons with – and I won’t keep you in suspence – they were.  But this also flies in the face of common advice given to persons choosing binoculars for astronomy – advice that up until a year ago I usually gave. And that is, you can’t hold these big binoculars steady – both because they are too large and heavy, and because they magnify too much.  And that’s true. What’s more, if you can’t hold them steady, you shouldn’t be able to see difficult things – and that’s not entirely true.

The standard wisdom is that 10X50 binoculars are the largest binoculars the typical person can hold steady and so are the best for handheld astronomy. It’s not bad advice. But it isn’t entirely true. It depends on exactly what you want to do with them. If you want to be able to wear them around your neck all night and frequently hold them to your eyes for long, thoughtful gazes at the Milky Way, I agree – go for the 10X50s. They won’t wear you out and they will give you a lot of good time with the stars.

But – if like me – you want to use them for an occasional look in the course of an evening – and if you want to be able to see fainter stars and even fainter nebulae, clusters, and galaxies, I recommend the 15X70s and I will even go so far as to recommend the Celestron 15X70 Sky Masters because I’ve had good luck with that brand and model and it usually can be had for between $50 and $80 and they are surprisingly good for the price – though I do urge you to get a better, padded strap to go with them. The one that comes with them is too dinky.  And treat them gently. Most binocular optics will get out of whack if they are dropped, or bounced around.

Here’s the sort of thing you are hoping to see:

How Jupiter's moon might appear at one specific moment - in this case a moment when they were all on the same side of the planet. Of course the next night the view could be quite different. The letters stand for Europa, Io, Ganymede, and Callisto.

And keep in mind this view will occupy only a small part of the center of your binocular field of view.

The largest circle represents the typical field of view with low power binoculars. The next circle shows the field with 15X70 binoculars - and the green circle represents the amount of space Jupiter and its moons will occupy in such a field of view - quite tiny, but Jupiter is so bright it will seem bigger.

So back to Jupiter. I had a clear sky with Jupiter well up in the west.  I stepped out onto my deck with all three pair of binoculars and tried to see Jupiter’s moons with first one and then the other. Nothing. I could not see a single Moon. Why? Two reasons.

First, my eyes were not dark adapted and the moons are a faint target. They look like stars and their magnitudes may fool you into thinking you can see them quite easily, for they are as bright as some of the faintest stars we see in areas where light pollution isn’t a big problem. But they are very near an incredibly bright object – Jupiter – which in October will be very close to magnitude -3 – only Venus, the Moon, and Sun are brighter!  Since the moons are generally within 10 arc minutes or less of the planet – think of that as about 10 planet diameters – they frequently get lost in the glare of Jupiter. And that brings us to the second issue – focusing the binoculars.

Binoculars need to be precisely focused for this task and that isn’t as simple as it sounds. First, a lot of people don’t know that it’s a two-step process to focus binoculars. With the typical center-focus binocular you need to look through the binocular, close your right eye, and focus with the center wheel. When the object is sharp in your left eye view, then close the left eye and now focus the right side using the diopter setting – that  means turning the knob that surrounds the eyepiece on the right. (This isn’t always obviously marked as such – just try turning the right eyepiece as you look through it.)  This brings both sides of the binocular into sharp focus and accounts for any difference between your eyes. Not difficult – but on a dazzling object such as Jupiter against a dark sky I had to do this repeatedly with each pair of binoculars before I was satisfield I had a really sharp view.

And this is where you will first notice how difficult it is to hold any binocular – but especially the larger ones – steady.  Focusing on a bird or quarterback or race horse is far easier. We usually don’t demand such precision out of what are – in all but the most expensive – quite crude optical instruments.  The stars put these inexpensive optics to the test.  So be patient. Do your best to get Jupiter to quiet down and sit still and be round.

And by the time you do – Voila! Bet your dark adaption will be pretty good. If it isn’t, give yourself 10-to-15 minutes in the dark  – no flashlights or other white light – to get your eyes properly adapted.

Now those two things out of the way I decided to do this the hard way. I knew the largest binoculars would give me the best view, so I didn’t want to prejudice things by looking first through them.  I wanted to pretend the smallest was all that I had.  So I looked first with the 8X40 glasses  and after about a minute of careful observing, a tiny dot of light popped into view on the west side of the planet.  Aha! A moon. Probably Ganymeade because it’s the largest and brightest.

That I saw while standing up.  I then went in and got a pillow, brought it out and lay down on the deck. This was better. I saw Ganymeade quite easily and the more I looked I saw there was a second moon closer to the planet – probably Europa or Io, but I couldn’t be sure – any of the moons can appear to be close – it’s just that Europa and Io never wander too far away from it, while Callisto can be quite far out – or in our line of sight, appear to be quite close.

I later brought out a comfortable deck chair and it proved to give me almost as good views as I got lying down – I could hold the binoculars steadier sitting than standing.

I should add here that I have good straps on all the binoculars and sometimes I push my elbows through the straps and spread them out to give me  a steadier grip. You can get quite fancy with this approach, using the strap in various ways much as soldiers and competitive shooters learn how to use a rifle sling to steady it.

There is a ton of excellent advice with pictures on how to hold binoculars steady here. And you can mount them on a camera tripod.  Many places sell an inexpensive adapter, such as this one,  that works with most binoculars.  The problem with this tripod approach is the higher things get the more awkward it is to look through the binoculars – so don’t wait too long. When Jupiter is about 30 degrees up – three fists above the horizon – would be a good time to give this tripod approach a try. More elaborate parallelogram mounts for binoculars are great fun, but can cost significantly more than the binoculars and sort of defeat the purpose of having a light weight, easy to carry and use observing tool.

But back to the handheld tests. I had certainly seen one moon and gotten hints of a second and the slightest whisper of a third. How did the 11X56 do? About the same. Except with the larger binoculars the  “hints” turned into certainty for the second moon and there was, from time to time, solid suggestions of a third moon out well beyond Ganymeade – which could only be  Callisto. This business of now-you-see-it, now-you-don’t is not unusual with faint astronomy objects. Our sky conditions rapidly change giving us clear, momentary looks at things that are on the edge of the capabilities of our eyes and instruments.

When I switched to the 15X70s all three moons were confirmed and really quite easy – yet I will remind you, before dark adaption and careful focusing, I wasn’t seeing any of the moons even with these larger binoculars.

And that was it. I did a lot more observing and retesting and being sure of my views through each binocular and the more I observed the easier it got – and the more just plain satisfying. Galileo would have loved any of these binoculars. Knowing exactly where to look and what to expect is a big help. The moons will always be pretty much in a line with the equator of the planet – but they can be on either side of it and one or more may be hidden from view at any given time and all might be quite close, or all on the same side. And the line holding the moons may tilt upward or be level, or tilt downward depending on the position of Jupiter in the sky. So while much of the universe is unchanging – at least on our time scale – this is one part that changes constantly.

If this is your first time looking for the moon, do yourself a favor. Go to this page at the Sky and Telescope Web site and open the JavaScipt utility.  It will tell you right where the moons are – and which is which – for any given moment. On the morning I looked, here’s what that utility showed me.

Screenshot of javascript utility at Sky and Telescope showing positions of Jupiter's bright moons.

Notice all four moons were on the same side, but one, Europa, was too close to the planet for me to see! So the bottom line is this. I saw all three moons with all three binoculars once my eyes were dark adapted and t e binoculars were well focused and I was sitting or lying to hold them steady.  But despite the difficulty of holding the binoculars steady, the biggest gave me the brightest and best view.

Ghostly light, meteors, and the Moon this month

The ghostly light I refer to is the zodaical light which is sometimes known as false dawn. In the fall it is best seen in September and October in the morning – and you must do it in an area that has dark skies – skies which reveal the Milky Way – and at a time when there is no competition from the Moon which would easily drown it out. For this fall that means you best bet is the first week or so of October. You need to pick your time carefully – between two hours and 80 minutes of sunrise. You look in the east and what you;re trying to spot is a wide, conical light rising fromt he eastern horizon.

If you go out looking for Mars in the early morning at the start of the month, be sure to include alook for Zodaical Light once your eyes are well dark adapted.  You’ll find more details about it near the bottom of this post.

On the meteor front I think the best bet this month is the Orionids which should be best on the morning of the October 22 – but don’t expect anything spectacular. The Moon will be a waning crescent and offer some interference and this “shower” is really just a drizzle. Other may put more emphasis on the Draconids because they are expected to be intense for a brief period on October 8th, but with the Moon nearly full that night it’s hard to imagine seeing anything but a few of the very brightest.

And speaking of the Moon, it is at first quarter on October 3, full on October 11, at last quarter on the 18th and new on the 26th. It will be quite close to Jupiter on the nights of October 12, 13, and 14, but even though near full, will not over power the brilliant planet. That is, jupiter will be easily visible, though stars in that vicinity will not.

On October 28th The Moon and inner planets will put on a challenging display in our western sky with Venus and Mercury. The Moon is  two days old and shouldn’t be too hard to  find. Venus is brilliant at magnitude -3.9 (a full magnitude brighter than Jupiter) and though very close to the horizon, should also be fairly easy with binoculars and clear skies. Mercury? Good luck. It’s around magnitude zero, so significantly dimmer than Venus, but brighter than the star Antares – but it is so close to the horizon you’ll have to have a completely unobstrcuted view and awfully good luck with clouds. I’d start looking about 10 minutes after sunset using binoculars. Our chart below is for half an hour after sunset. Much later than that and everything will be too low to see – or have set. Even at that time the Moon is just six degrees above the horizon- roughly half a fist!

Chart is for half an hour after sunset on October 28, 2011. Prepared from Starry Nights Pro screenshot.

Events October 2010 – A Primetime Comet and the King’s Moondance

Comet Hartley 2 is the big observing news for October 2010, but the King of Planets, Jupiter, also will be putting on a prime time show all month with its four dancing Galilean moons. (Jump to Jupiter details here.) Venus and Mars, while technically still visible, are quickly closing in on the Sun in the west. Mercury is diving back towards the Sun in the morning sky, and while Saturn emerges in the morning sky, it won’t be high enough for a decent view until near the end of the month.

Ah, but there’s that comet! A “dirty snowball” that meanders roughly between us and Jupiter as it circles the Sun every six years. Its orbit, according to this wonderful applet at the Jet Propulsion Lab, looks like this. Notice how close it is to our little space station Earth on October 7 – that’s a good thing!

The outer white circle is the orbit of Jupiter. Hartley’s elliptical orbit is represented by dark blue for that portion below the plane of the solar system - light blue for when it is above the plane. This snapshot shows its location during a prime observing opportunity October 7. However, it will be easy for those in mid-northern latitudes to find throughout the first couple of weeks of October. (Click image for larger version.)

So let’s start the month with Hartley 2. This tiny periodic comet will:

  • Come closer to Earth than it ever has before – just 11 million miles;
  • Be easily found by binocular users in prime time well away from the Sun – and may even reach naked eye visibility;
  • Will be visited by a US space craft November 4, 2010, for some close up images in the hopes of learning more about these fascinating objects.
  • Finally, there’s always the possibility that it won’t behave as predicted. It may be dimmer – it may be brighter – even a lot brighter. Probably not – but after dull and dim Comet Holmes shocked everyone by brightening overnight by a factor of about half a million times in October of 2007 – well, comets need watching!

Generally, comets become brightest as they near the Sun – but this also can make them tricky to see. It’s usually a race with two opposing forces conspiring to make life difficult for the observer: As the comet gets closer to the Sun, it gets brighter. But as it gets closer to the Sun it also gets lost in the twilight glow. Such comets are frequently at their best just after sunset, or just before sunrise. This will not be the case with Hartley 2. Comet Hartley 2 will be a prime time comet for Northern Hemisphere observers. Figure on getting your best views of it during the first two weeks of October at a convenient evening hour, such as 8 pm. And circle October 7 as an especially fun time to take a look if the weather gives you a break. What makes October 7 so special? Well, the comet happens to be passing a favorite deep sky object that is also easily visible in binoculars. In fact this object, the famous Double Cluster in Perseus, is relatively easy to find with binoculars and if you can find it, you should be able to spot the comet in the same field of view. Here’s a guide chart I’ve modified some from a Starry Nights Pro screen shot. Notice that the Double Cluster is conveniently placed between two familiar asterisms – the “W” of Cassiopeia and the “Bow” of Perseus. Careful scanning between those two should be enough to reveal it, though the big problem most newcomers have with recognizing deep sky objects with binoculars and small telescopes is they don’t know what they can expect to see. So first here’s what I consider a reasonable simulation of the appearance of the double cluster in typical, hand-held binoculars.

A typical view of the Double Cluster in binoculars? Well - I think this is a pretty close match. It's a slightly Photoshopped version of a Starry Nights Pro screen shot that I hope will give you an idea of what you should expect to see. Of course exactly what you see depends upon your skies, your binoculars, and your eyes! And if you look on the night of October 7, 2010, there should be an extra fuzzy object in the view - Comet Hartley. (The Double Cluster is two open clusters containing hundreds of relatively young stars about 7,000 light years away.)

And here’s the guide chart for finding the Double Cluster and Comet Hartley 2 during the first couple of weeks of October.

Finding Comet Hartley 2 the first couple of weeks in October 2010. Click image for larger view. (Prepared from Starry Nights Pro screen shot.)

As the chart above shows, September 30 would be a great time to look for this comet because it will be so near the Alpha star of Cassiopeia – the “W.” Each day it continues in a generally eastward direction. The red circle is a 5-degree field, typical for 10X50 binoculars. (Your binoculars may show a larger field of view.) The comet enters near the top of the circle on October 6, is at the position shown on October 7, and will be exiting the circle at the bottom (eastern side) on October 8. On October 12 it will be about four degrees north of Mirfak. Remember – to find north in the sky just draw a line between a star and Polaris – in this case between Mirfak and Polaris – Comet Hartley should be pretty close to such an imaginary line on October 12.

After that it will continue its eastward path, coming closest to the Earth on October 20. However, after the 12th the moon starts to come into play during prime time and for the next two weeks it will dominate the evening sky, its light making the comet and other faint objects more difficult to see. That’s why the first two weeks of the month are best for this event, but of course the comet can be found later and will continue to be a fairly easy telescope object right through November, though at that point it starts to favor Southern Hemisphere observers. By November it’s down below Orion moving towards Canis Minor and so isn’t high enough to see until around midnight. Still,  it should be fun to look at it November 4th at the same time the comet is on NASA’s “candid camera.” For a more detailed chart for finding it on other dates, go here.

Now why all the excitement about a comet? They have a long history of scaring people – of being signs of impending disaster – but of course that’s from the days when we knew much less about them than we do now. Observing a bright comet in 1957 is one of my first memories of the night sky. Later I got my start in free lance magazine writing when I introduced the readers of Popular Science to Comet Kohoutek – the “Comet of the Century.” Well it wasn’t. My writing career survived that since I was quoting reliable scientific authority, but it sure bruised my ego when Comet Kohoutek never developed to anything like what was predicted.

That was my most shocking comet until 2007. That’s when Comet Holmes suddenly burst on the scene – and I mean burst. One night it was an incredibly dim magnitude 17 object visible only to professional astronomers and amateurs with extremely large telescopes – and neither the professionals nor the amateurs were much interested in it. Such faint comets are fairly common, and this one had been seen on repeated visits since 1892. But in just a few nights it was easily seen with the naked eye. Amateur star gazers were dazzled. It was a bright, round cloud in the same general area of the sky as Hartley 2 will travel through this fall. Yet it was farther away – out beyond the orbit of Mars and oriented so that from Earth we were looking right down the barrel, so to speak. That is, it had a tail, but the tail of a comet always points away from the Sun and in this case it was pointing directly away from us.

That fuzzy blob just kept growing so that for a brief time it was actually the largest object in our solar system – though it was, of course, a big fluff ball consisting of next to nothing. And while scientists have their theories on how all this came about, no one is sure. The puzzles that continue to surround comets is why NASA, after visiting another periodic comet in 2005, decided to take a close look at this one as well. What will they see? Not much, I suspect. That is, not much in terms of what the average person will be able to interpret from the pictures. But presumably some more pieces of the comet puzzle will fall into place. As reported on Gary Kronk’s authoritative “Cometography” site – bookmark that one for future reference – here’s the plan:

The Deep Impact spacecraft, which studied periodic comet 9P/Tempel 1 in 2005, will examine 103P/Hartley 2 during the period of September 5 to November 25, 2010, as part of the EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) mission. The closest approach occurs on November 4, when the minimum distance to the comet will be only 620 miles (1000 kilometers). The spacecraft will use two telescopes with digital color cameras and an infrared spectrometer. The latter instrument will determine the chemical composition of outbursts of gas from the comet’s nucleus.

And what will we be looking at? Comet Hartley is small even for a comet – about three-quarters of a mile across. (In comparison Comet Tempel 1 is thought to be 8.7 by 2.5 miles in size.) The revised general description for comets these days is a dirty snowball with a crust. Think of it a moment. Comets are not just any old chunk of rock. Millions are thought to reside in the Oort Cloud out at the farthest reaches of our solar system – about one light year away. They are thought to be pure examples of the original material of the cloud of gas and dust from which we were all formed – yes, I mean you and I. Seeing a comet up close is roughly akin to the ultimate of finding something really cool in your grandparents’ attic! So don’t get them confused with the other rocks that tend to float around nearby. We call those asteroids, and we worry some about them colliding with the Earth because such a collision would produce a major disaster. And, of course, a collision with a comet even as small as Hartley 2 would produce a major disaster. But comets and asteroids, while looking similar when far away from the Sun, are really quite different beasts. The visit to Comet Hartley 2 will include no pyrotechnics – Deep Impact has done its thing as far as throwing stuff at comets is concerned. Still, this picture of the mission to Tempel 1 when we shot a probe into it gives you a feel for what a comet looks like close up. It will be interesting to compare this photo with what we see in early November.

The Tempel 1 mission included striking the comet with a spacecraft to cause an explosion and learn more about its makeup. From the NASA press release accompanying this picture: “This spectacular image of comet Tempel 1 was taken 67 seconds after it obliterated Deep Impact's impactor spacecraft. . .. The image reveals topographic features, including ridges, scalloped edges and possibly impact craters formed long ago.” CREDIT: NASA/JPL-Caltech/UMD

Meanwhile, out at Jupiter, the moons are doing their thing

An hour after sunset on October 1, Jupiter is already 15 degrees high in the eastern sky. It’s by far the brightest “star” in the east, so you can’t miss it. Each night it will a bit higher at the same time, and the higher it gets the easier it is to see detail and the moons using a telescope or binoculars. (Uranus is still nearby as well. If you want to try to spot it, see this post with charts from last month.)

Jupiter is a favorite sight in small telescopes – and to see the four Gallilean moons you really should use a telescope – any telescope. I have a tiny, 50mm “department store” telescope that mounted on an ordinary camera tripod does an excellent job showing the moons of Jupiter. It is possible to see them with binoculars if you have good eyesight and can hold the binoculars really steady – lean against a building, or better yet, mount them on a tripod.

Here’s a simulation of how the moons change position in a single evening. The changing tilt of the plane of the moons is due to the changing position of Jupiter in the night sky.


The moons shown at the start of the video are, from left to right, Callisto, Ganymede, Europa, and Io. The video simulation was made using Starry Nights Pro software.

They’re called the Galilean moons, of course, because Galileo discovered them four hundred years ago when he pointed a small telescope at the sky. The sight shook up the world! At that time most folks believed the Earth was at the center of the universe and everything revolved around it. A bit conceited, perhaps, but darn, watch the sky on any given night and it sure looks like we’re at the center of things! But here comes Professor Galileo with his new-fangled looking glass, and he points it at the bright “wandering star,” Jupiter, and what he sees is another world. Not only is it another world but a world with four little worlds clearly whirling around it! And of course he rushes right into print with this astounding discovery publishing his “Sidereus Nuncius” or “Starry Messenger” in March of 1610. Today many amateur astronomers enjoy studying details on this largest of planets. I love watching Jupiter’s four brightest moons. Here’s why:

  • You can see them with any small telescope – even binoculars if you can hold them really steady.
  • They do something! Most astronomical objects don’t change much over our lifetimes. Jupiter’s moons can go through significant changes in a single night as the video above shows.
  • These four bright moons played a major role in changing our view of the universe.
  • They even helped us determine the speed of light a couple of hundred years ago, something next to impossible to determine on Earth without modern, sophisticated instruments.
  • For the telescope user they:
  1. duck in and out of Jupiter’s shadow (eclipse)
  2. hide behind the planet and suddenly pop out (occultation)
  3. cross in front of the planet providing a challenge for telescope users to spot them (transit – this is what Io does in the above video)
  4. and from time to time they cast their shadows on the giant planet – shadows visible in a backyard telescope as perfect round circles
  • Hubble and modern spacecraft have shown us that Jupiter’s moons are full of surprises. No two are alike and all four are different than what scientists imagined before the spacecraft got out there and gave us an up-close and personal view.
  • All of which is incredibly awesome when you understand that the little lights you see moving with grace, precision, and predictability are complete worlds in themselves the size of our moon or larger. (Ganymede is about 1.5x the diameter of our moon.)

jupiter_moons

How do you know which moon is which?

If you want to know which of Jupiter’s moons is where on any given night, use this neat little online utility provided by Sky and Telescope magazine. Now the basics. Jupiter has 63 moons, but only four of them are easily seen in small telescopes. Here are their names – in order moving outward from the planet – and links to more details about each.

Oh – and about determining the speed of light. Think about it. I believe Galileo once took a stab at this by stationing observers facing one another from different mountain peaks. They then uncovered a lantern at a predetermined time. No luck. Light is much too fast for this kind of experiment. Hey – light could go completely around the Earth more than seven times in a second! But here’s how Jupiter’s moons helped determine the speed of light more than 300 years ago! These kinds of discoveries always leave me in awe at how brilliant the discoverers were and how precisely they were able to make observations with tools that were not nearly as good as the inexpensive telescopes available to anyone today. The account which follows can be read in full here. It is from a posting by Michael Fowler of the University of Virginia Physics Department. One more thing to appreciate as you watch Jupiter’s moons.

The first real measurement of the speed of light came about half a century later, in 1676, by a Danish astronomer, Ole Römer, working at the Paris Observatory. He had made a systematic study of Io, one of the moons of Jupiter, which was eclipsed by Jupiter at regular intervals, as Io went around Jupiter in a circular orbit at a steady rate. Actually, Römer found, for several months the eclipses lagged more and more behind the expected time, but then they began to pick up again. In September 1676, he correctly predicted that an eclipse on November 9 would be 10 minutes behind schedule. This was indeed the case, to the surprise of his skeptical colleagues at the Royal Observatory in Paris. Two weeks later, he told them what was happening: as the Earth and Jupiter moved in their orbits, the distance between them varied. The light from Io (actually reflected sunlight, of course) took time to reach the Earth, and took the longest time when the earth was furthest away. When the Earth was furthest from Jupiter, there was an extra distance for light to travel equal to the diameter of the Earth’s orbit compared with the point of closest approach. The observed eclipses were furthest behind the predicted times when the earth was furthest from Jupiter. From his observations, Römer concluded that light took about twenty-two minutes to cross the Earth’s orbit. This was something of an overestimate, and a few years later Newton wrote in the Principia (Book I, section XIV): “For it is now certain from the phenomena of Jupiter’s satellites, confirmed by the observations of different astronomers, that light is propagated in succession (note: I think this means at finite speed) and requires about seven or eight minutes to travel from the sun to the earth.” This is essentially the correct value.

Less successful was an idea they had much later that they could solve the problem of finding one’s longitude – while at sea – by observing the moons of Jupiter. This was very seriously pursued because knowing longitude is critical to navigation and the accepted method involved using a very precise clock that kept correct time throughout a long sea voyage. It was hard enough to make a very precise clock – but one that retained its precision when subjected to the knocking about and unavoidable moisture that was part of any long voyage by sail? Nearly impossible. (See the wonderful book, “Longitude,” by Dava Sobel, for the story of how they did solve this.) But that said, as you watch the moons of Jupiter with a small telescope, try to imagine doing this on the heaving deck of a sailing ship with a telescope that is significantly cruder than the one you buy today! Then imagine that your life may depend on the result! Makes you appreciate the GPS if nothing else ;-)

So get out some night this month and take a close look at our neighbor, Jupiter. And if possible, see if you can see the moons. Newton is playing the tune, and the moons do the dance – music of the spheres indeed!

 

UPDATE – October 14, 2010 – Spent a nice hour  this morning (4 am – 5 am) with Comet Hartley 2 – well, too much of that time trying to figure out how to find it with the Orion 110ED which is mounted on a parallelogram mount in my observatory and gets kind of complicated to point near the zenith. But I found the comet in just 30 seconds of looking with the 15X70 Celestron binos. That was easy and the comet seemed significantly larger and brighter than it was in my other observations of the past week. In ease of finding with those binoculars I would put it about halfway between M33 and M31. It seemed larger in the binoculars, as well. It was not nearly so easy inthe 8X50 finder – but certainly clearly visible.

Once I figured out how to twist and turn the 110 so it was pointed at the right section of sky – this is a very rich area about 6 degrees east of Mirfak – it showed very nicely in the 110mm. Yes, I could see a tail. I drew the stra field and sketched the comet and I had the orientation of the tail correct – but I was not confident I was seeing the tail until I checked my sketch against the charts. In other words, the tail is faint. In binoculars the comet reminds me very much of Holmes – especially since this is the same region Holmes inhabited when it was quite bright. But Hartley is moving much, much faster.

With the binos it was simply a blob – a puff of smoke among – and overlapping – some faint stars. In the 110mm it took on a solid nucleus – not star-like – larger – and a clearly defined coma. I kept changing the estimate of the coma’s size as I went from a 24mm Panoptic to Naglers of 13, 7, and 3.5 – that last is 236X. With each increase in magnification my estimates got smaller – not because I was seeing less of the comet – it took magnification well- but because I tend to think and object is taking up a greater percentage of the eyepiece than it is. Once more my sketch came to the rescue. It was easy to compare it to the known starfield and get an accurate measurement of 9 minutes of arc across for the clearly visible coma. I would put what I felt I could identify as a tail at about two or three times that. Be interesting to see what the photos show. My estimates are strictly about what I can see with what I’m using under dark and transparent skies -the transparency being a 4 out of 5 with 3 being average.

It is really a morning object now, with the moon starting to  drown it out in the early evening.

UPDATE: October 7, 2010 -Comet Hartley 2 now visible in “normal”  binoculars! Last night it was bright enough for me to see  using 8X40 binoculars – significantly brighter than on October 2 when I last saw it. It was an easy target in 15X70 binoculars and I suspect that at this rate it will be reaching naked eye visibility – just barely – for those with really dark skies..  But even with small binoculars it’s still the kind of target that requires an   observer to have some experience  to find and see. For example, if you can find and see the large galaxy, M33, you certainly should be able to use the same instrument to see Hartley now.UPDATE: October 2, 2010  – While I would not discourage people from searching for Comet Hartley 2  right now, it is something that only experienced observers with dark skies will find easy to see at this moment. I have mag 5.5 skies and I could not see it last night while using 15X70 hand held binoculars when it was  about 50 degrees above the horizon in the early evening. I did see it with an 80mm telescope and it was visible to one of three new observers who were visiting me last night when we used a 6-inch refractor. I would rate it a bit more difficult to see than M110, the fainter of the companion galaxies to M31. 

Meanwhile, Spaceweather.com said early today that “some observers are reporting that comet 103P/Hartley 2 has reached the threshold of naked eye visibility.” I wrote them challenging those reports. No response, but I noticed that by 2 pm the earlier update had been taken down and a new one replaced it – one that makes no mention of “near naked eye visibility.

Sky and Telescope does report that it should brighten significantly over the coming week. I hope so. I worry about giving eager newcomers the wrong impression when we say – as I have done – that this is visible in binoculars. It may be in a  few days –  or to experienced observers with very dark skies right now – but not to more casual observers who have to cope with typical, suburban light pollution!  While Comet Hartley 2 makes its closest approach on October 20  and should be brightest then, it will be difficult to see at that time because it will be fairly low in the evening sky and a nearly full moon will be drowning it out. I suspect the best time to see it will be around October 12 before the Moon offers significant interference.  Perhaps then it will be visible to more casual observers using binoculars.

That said, it is an incredible sight in a large telescope.  I observed it with my 15-inch reflector last night and was just blown away to think that so small an object – about three-quarters of a mile across – could kick out such an incredible dust cloud that we can see it from such a distance. If Comet Hartley 2  was a huge rock on the Moon I would not have a prayer of seeing it at just 3/4 of a mile across, even with the 15-inch. But it is about 50 times farther away. I haven’t done the calculations, but that cloud of dust I’m looking at has to be quite huge and is reflecting an awful lot of sunlight to make it visible to me. That’s awesome!

Jupiter’s moons pull a vanishing act – and other neat dance moves!

(For an observing report on this event, go here.)

Jupiter’s four bright moons always put on a great show – ask Galileo – changing positions slowly in the course of the night. But for viewers in North America the night of September 2-3 offered an unusual opportunity because the four bright moons all played hide-and-seek at once – something that happens  about 20 times a century and I suspect much less for any given geographic area. That said, the following video and text I believe remainr elevant andhelpful for anyone interested in watching Jupiter’s moons. The  video is an animated simulation depicting events of one night. It was created in Starry Nights Pro astronomy software and time has been speeded up so  that what you see in about four minutes is what actually takes place in about seven and a half hours.

(For a complete explanation of what’s going on in this animated simulation – and what you should see September 2-3, 2009 – you can take this shortcut  to  the sequence of events below.)

Here’s why I love watching  Jupiter’s four brightest moons:

  • You can see them with any small telescope – even binoculars if you can hold them real steady.
  • They do something! Most astronomical objects don’t change much over our lifetimes. Jupiter’s moons, as you can see from the video simulation, go through significant changes in a single night.
  • These four bright moons played a major role in changing our view of the universe.
  • They even helped us determine the speed of light a couple hundred years ago, something next to impossible to determine on Earth without modern, sophisticated instruments.
  • For the telescope user they:
  1. duck in and out of Jupiter’s shadow (eclipse)
  2. hide behind the planet and suddenly pop out (occultation)
  3. cross in front of the planet providing a challenge for telescope users to spot them  (transit)
  4. and from time to time they cast their shadows on the giant planet – shadows visible in a backyard telescope as pefect round circles
  • Hubble and modern spacecraft have shown us that Jupiter’s moons are full of surprises.  No two are alike and all four are different than what scientists imagined before the spacecraft got out there and gave us an up close and personal view.
  • All of which is incredibly awesome when you understand that the little lights you see moving with grace, precision, and predictability are complete worlds in themselves the size of our moon or larger. (Ganymede is about 1.5x the diameter of our moon.) Newton is playing the tune, and the moons do the dance – music of the spheres indeed!

jupiter_moons

You can enjoy Jupiter’s bright moons any night the planet is visible. What’s special about the night of September 2 and 3 of 2009 is they’re going through their complete routine in one night and for a couple hours all four of them are out of sight for all practical purposes, but still providing an interesting challenge for the telescope user. What’s more, Jupiter is very close to the moon on this particular night  and very bright in the southeastern sky,  so it is easy to find. And any small telescope will reveal the moons. Seeing them with binoculars is possible, but it takes sharp eyes and a steady hand. I’ve never been able to see them with binoculars unless I can steady the binoculars on a tripod, or against the corner of a building or some other support.

The moons were discovered by Galileo 400 years ago and he didn’t waste any time writing about his findings in his “Starry Messenger.” What he had to say shook up the religious/philosophical/scientific establishment of the day. Although Copernicus had argued otherwise more than 50 years before, the common belief remained that the Earth was the center of the universe and everything revolved around the Earth. But a few nights of observing Jupiter’s moons and that whole business of us being at the center of everything went out the window. Obviously Jupiter was at the center of its own little system and these moons were revolving around it, not us.

The  13-day-old Moon and Jupiter dominate the eastern sky near the horizon for North American observers on September 2, 2009. This screen shot from Starry Nights software captures the positions, but don't get the idea that Jupiter looks thatbig - the size represents its brightness - and its is fa rbrighter than any of the stars, though to the naked eye it will look like a star.

The 13-day-old Moon and Jupiter dominate the eastern sky near the horizon for North American observers on September 2, 2009. This screen shot from Starry Nights software captures the positions, but don't get the idea that Jupiter looks that big - the size represents its brightness - and its is far brighter than any of the stars, though to the naked eye it will look like a star.

Now, with any small telescope, you can travel in the footsteps of Galileo, observe Jupiter’s moons, and make your own drawings. This month (September, 2009) is a good time to start because Jupiter appears in our eastern sky as the Sun is setting in our western sky. By about half an hour after sunset Jupiter will put in an appearance. The only thing brighter than it in the eastern evening sky this month is the moon. And on the evening of September 2 folks in North America will see a nearly full moon pretty close to Jupiter – exactly how close depends on where you are and when you look. On the East Coast at 8 pm EDT the moon will be less than 3 degrees from Jupiter in the southeast and pretty close to the horizon. About 7 hours later it will be in the southwest and the moon will still be with it, but the separation will have increased to about five degrees. (Typical binoculars have a field of view of about 7 degrees, so you should easily see both the moon and Jupiter in the same binocular field.  The question – which I honestly can’t answer – is how easy will it be to see Jupiter’s moons with our own moon shining so close to it? Will the moon drown them out? I’m pretty  confident this won’t be a problem for telescope users. It may make it  difficult for binoculars users since the moons of Jupiter are roughly as bright as the faintest stars we can see with our naked eye.)

What should you look for an when?

First, if you want to know which of Jupiter’s moons is where on any given night, use this neat little online utility provided by Sky and Telescope magazine.

Now the basics. Jupiter has 63 moons, but only four of them are easily seen in small telescopes. Here are their names – in order moving outward from the planet – and links to more details about each.

Sequence of events September 2-3

Here is the schedule of events in  EDT, with  24-hour format Universal Time in parenthesis. (Data is from a listing in the September Sky and Telescope.)  If clouds, sleep, or work cheat you out of a live view, you still might refer to the following list as you watch the animation.)

September 2

7:19 pm (23:19)Callisto is occulted – goes behind the planet. (This will be in daylight for US observers, but when you start observing Jupiter later,  know that Callisto is already behind it.)

11:43 pm (3:43 Sept. 3) Io is occulted – goes behind the planet. (This is fun to watch – how long does it take Io to vanish? )

11:58 pm  (3:58 Sept. 3)Europa transit begins on the opposite side of the planet from where you saw Io vanish a few minutes before. Seeing the moon against the bright disc of the planet is possible in small telescopes, but varies in difficulty depending on exactly what part of the planet is behind the moon, some parts being darker in hue than others. But keep in mind, these moons are so far away that even in a large, backyard telescope they barely show a disc under ideal conditions. So what you are look for is a point of light not much different than a star.

September 3

12:43 am (4:43)Ganymede follows Europa onto the planet’s disc. Is it easier to see than Europa? It’s significantly larger, so might be a tad easier, but again, it takes a large telescope to show the moons as even a small disc.

12:56 am (4:56)Europa’s shadow follows it onto the face of Jupiter – but it may be easier to see as it gets nearer the center. It also may help you pick up the disc of Ganymede – the shadow of Europa during the first half of its journey is very close to the disc of Ganymede – at least as shown by the Starry Nights Pro simulation.

2:29 am (6:29)Io pops back into view – but look where it is! It’s not close to the planet when it does this because after it was hidden by the disc (an occulation) it went into the planet’s shadow – technically, an eclipse. So what you see is it emerging from the shadow, already some distance out from the planet.

2:42 am (6:42) Ganymede’s shadow enters the disc.  Notice how far behind Ganymede it is? Europa’s shadow was much closer to it. Why? Because Europa is much closer to the planet then Ganymede and here’s proof!

2:49 am (6:49) Europa emerges from the disc – but if you have not been able to follow it when it was on the disc it may be difficult to pickup for few minutes because it will still be close to Jupiter and lost in its glare – at least to the smallest telescopes and binoculars. However, Europa’s shadow will still be visible on the disc for almost another hour.

3:47 am (7:47) Europa’s shadow goes off the disc.

At this point East Coast observers are seeing a Jupiter that is very close to the southwestern horizon and the moons will be difficult to observe. For my location – at 71 degrees longitude (Westport, MA). the giant planet sets about 4:30 am.

4:20 am  (8:20)Ganymede’s transit ends, but it’s shadow is still on the planet.

4:35 am (8:35) – At last! Here comes Callisto! For me it has been out of sight all night. It goes behind the planet before it is dark enough to see it and doesn’t come out until after Jupiter has set. However, folks farther west should certainly see this exit event.

6:21 am (10:21)Ganymede’s shadow exits the planet’s disc. Hey – that’s all folks – for tonight. But there are many other nights when there are interesting events.

Be sure to check Sky and Telescope Javascript utility.  Any night Jupiter is well placed for observing I always check this little utility to see if there are any neat events coming up at a convenient time. Nights like September 2-3, 2009 are rare. But with four moons there are frequent times when one or the other is doing something interesting.

How to time a light beam!

Oh – and about determining the speed of light. Think about it.  I believe Galileo once took a stab at this by stationing observers facing one another from different mountain peaks. They then uncovered a lantern at a predetermined time.  No luck. Light is much too fast for this kind of experiment. Hey – light could go completely around the Earth more than seven times in a second! But here’s how Jupiter’s moon helped determine the speed of light more than 300 years ago! These kinds of discoveries always leave me in awe at how brilliant the discoverer’s were and how precisely they were able to make observations with tools that were not nearly as good as the inexpensive telescopes available to anyone today.  The  account which follows can be read in full here. It is from a posting by Michael Fowler of the University of Virginia Physics Department. One more thing to appreciate as you watch Jupiter’s moons.

The first real measurement of the speed of light came about half a century later, in 1676, by a Danish astronomer, Ole Römer, working at the Paris Observatory. He had made a systematic study of Io, one of the moons of Jupiter, which was eclipsed by Jupiter at regular intervals, as Io went around Jupiter in a circular orbit at a steady rate. Actually, Römer found, for several months the eclipses lagged more and more behind the expected time, but then they began to pick up again. In September 1676, he correctly predicted that an eclipse on November 9 would be 10 minutes behind schedule. This was indeed the case, to the surprise of his skeptical colleagues at the Royal Observatory in Paris. Two weeks later, he told them what was happening: as the Earth and Jupiter moved in their orbits, the distance between them varied. The light from Io (actually reflected sunlight, of course) took time to reach the earth, and took the longest time when the earth was furthest away. When the Earth was furthest from Jupiter, there was an extra distance for light to travel equal to the diameter of the Earth’s orbit compared with the point of closest approach. The observed eclipses were furthest behind the predicted times when the earth was furthest from Jupiter.

From his observations, Römer concluded that light took about twenty-two minutes to cross the earth’s orbit. This was something of an overestimate, and a few years later Newton wrote in the Principia (Book I, section XIV): “For it is now certain from the phenomena of Jupiter’s satellites, confirmed by the observations of different astronomers, that light is propagated in succession (note: I think this means at finite speed) and requires about seven or eight minutes to travel from the sun to the earth.” This is essentially the correct value.

Less successful was an idea they had much later that they could solve the problem of finding one’s longitude – while at sea – by observing the moons of Jupiter. This was very seriously pursued  because knowing longitude is critical to navigation and the accepted method involved using a very precise clock that kept correct time throughout a long sea voyage. It was hard enough to make a very precise clock – but one that retained its precision when subjected to the knocking about and unavoidable moisture that was part of any long voyage by sail? Nearly impossible. (See the wonderful book, “Longitude,” by Dava Sobel, for the story of how they did solve this.)  But that said, as you watch the moons of Jupiter with a small telescope, try to imagine doing this on the heaving deck of a sailing ship with a telescope that is significantly cruder than the one you buy today! Then imagine that your life may depend on the result! Makes you appreciate GPS if nothing else 😉


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