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    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 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.

Look East! March 2010 roars in like a Lion – with Saturn tagging behind!

March roars into our eastern night sky like a lion – Leo, the Lion that is, led by the Little King “Regulus” and in 2010 brings Saturn with it. Just ahead of it is a special binocular treat, M44, a veritable beehive of stars barely visible to the unaided eye. Think of it as the lion’s whiskers. And don’t forget to look for the zodiacal light!

Leo does look much like the Lion depicted inthe 1603 Bayer catalog.  Click image for larger version.

The stars of Leo do indeed trace out some key parts of the Lion depicted in this plate from the 1603 Bayer atlas. (Click image for larger view.) Note that the bright star that marks the tail is named "Denobola," which in Arabic really does mean "tail." We encounter this also in the tail of Cygnus the Swan where the bright star is named "Deneb." The Arabic star names are frequently descriptive. (Image courtesy of Linda Hall library of Science, Engineering and Technology.)

 

I don’t usually put an emphasis on constellations, but in March it is fitting, for it makes it easy to remember what it is you see in the East just after sunset and besides, this is one of those constellations where when you connect the dots it looks something like it is supposed to look.

In fact, in my mind’s eye I can see the classic lion of the old Bayer star charts, but I more often see two very easy to remember asterisms – the Sickle that forms Leo’s head and mane, and the Triangle that forms Leo’s rump. And Regulus, our new bright guidepost star for this month, means “little king,” or “prince,” in Latin. That fits right in with the lion‘s reputation as King of the Beasts. And what a lovely image to have a prince leading a lion onto the night-time stage this month! Here’s our eastern sky chart. (As usual, click the image for a larger version, or download a printable version.)

Click image for larger view. Use link below to download a printer-friendly version. (Chart developed from Starry Nights screen shot.)

Click here to download a black-on-white (printer-friendly) version of this chart.

If you look in the same spot an hour or so later – or wait until mid-month, you will get the special treat of seeing Saturn, a favorite target for small telescopes, though this month it will be a tad disappointing to telescope users. Right now Saturn’s rings appear tilted as seen from Earth so that they make a thin line extending out from either side of the planet. In most years, they are at such an angle that they make a much better display. But Saturn is a special feature for this year, 2010. It won’t be back with the stars of Leo for another decade. So lets get on to the prime star in the east that’s there every year at this time, Regulus.

Is Regulus memorable in its own right? Well yes. It’s a star that is spinning so fast that if we could see its disc, it would look like a beach ball that someone sat on. It takes Regulus about 16 hours to make one rotation – in comparison our Sun, a smaller star, takes about a month to rotate. In fact, if Regulus were spinning just a bit faster, it would spin itself apart!

The rapid spinning gives Regulus an equatorial diameter that is about one-third bigger than its polar diameter. This also results in the polar regions of Regulus being much hotter than its equator.

Regulus is also a multiple star system, but as such rather dull visually. The second star in the system is much fainter, so it can barely be detected by a skilled observer using binoculars – and in a telescope it’s so far away from the primary star that they don’t seem like a pair at all. Both the primary and secondary are spectroscopic doubles – meaning the companions are so close we can’t see them with a telescope.

Though a relatively young star – about 250 million years as compared to the five billion year age of our Sun – Regulus is apparently nearing the end of its normal life as a “main sequence” star. That is, it’s about to finish burning hydrogen, which means it will soon go into the last stages of its life. But according to Jim Kaler, Regulus is also a curious case. It appears to have a very close white dwarf companion which scientists believe once was much larger and brighter than Regulus. But the gases were drawn from the white dwarf into Regulus making it both huge and bright and causing it to spin the way it does.

In total, Regulus is another example of how what looks like a common star to us, is quite fascinating when seen in the light of modern science.

Vital stats for Regulus:

• Brilliance: Magnitude 1.35, 22nd among the brightest stars in our sky; shines with the luminosity of about 150 Suns.
• Distance: 77 light years
• Spectral Type: B7V
• Position: 10h:08m:22s, +11°:58′:02

The buzz about the Beehive (M44), Mars, and Leo’s whiskers

In ancient times the constellation Leo extended much farther east and west, and M44 was considered to be its whiskers.

from “The Next Step – Finding and Viewing Messier Object” by Ken Graun

Whiskers indeed! I like that. It’s a great way to remember where to look for M44, for if you can find the Sickle – the huge head and main of Leo – then all you have to think is “now where would his whiskers be?” Scan 2-3 binocular fields in that direction – westward – and you should soon stumble upon M44, the Beehive. In 2010 this is especially easy. Start at Regulus and scan towards Mars, one of the brightest objects in the sky. M44 will be along this path, much nearer to Mars than to Regulus. Here is a chart you can use to find it – and to map the changing position of Mars, which will be especially interesting in March.

Following Mars and finding M44, the Beehive - or if you like, Leo's whiskers! Click chart to see larger image. (Chart developed from Starry Nights screen shot.)

Click here to download a black-on-white (printer-friendly) version of this chart that you can also use to chart the movements of Mars.

Over the next couple of months Mars will serve as a bright beacon making it easier to locate M44 whose other names are “the Beehive,” and Praesepe, which is Latin for manger. And if you have dark skies, away from light pollution, you will see this as a small, wispy cloud, perhaps suggestive of Leo’s whiskers. It is, in fact, a beautiful star cluster as binoculars or a small telescope will reveal. Galileo first discovered its true nature and in this hazy patch discovered more than 40 stars. You should see about that many with your binoculars. This is one of the nearest star clusters to us, and although there is still debate over its exact distance, it is around 580 light years. That compares with about 400 light years for the Pleiades. The two clusters are pretty close to the same size, but M44 is considered much older. M45 – the Pleiades – is estimated to be 78 million years old, while M44 is thought to be about 660 million years old. As star ages go, they’re both quite young.

The Latin name, Praesepe, is worth examining because it explains the names of two relatively bright stars which flank it – Asellus Borealis and Asellus Australis. Borealis means “northern” and Australis means “southern.” Asellus means “ass” – as in donkey – and Praesepe means “crib” or “manger.” In other words, the Beehive apparently looked to some like a pile of hay in a manger and these two flanking stars were donkeys, eating that hay, one to the north and one to the south. In binoculars the scene should look something like this screen shot from Starry Nights software to which I’ve added labels.

M44 and surroundings as it would appear in binoculars with a 5-degree field of view. Click image for larger view. (Chart derived from Starry Nights software screen shot.)

Click here to download a printer-friendly version of this chart.

The two donkeys are about as bright as the stars in the handle of the Little Dipper, so under dark skies should be faintly visible to the naked eye with the northern one the dimmest. The third star, Eta Cancri, is dimmer still. Its name, however, indicates that it, the Beehive, and other stars shown here are all part of the rather obscure constellation known as Cancer, the crab.

There’s a revealing naked eye exercise buried here as well. This is a good month to chart the course of Mars across the background of stars. Mars starts out the month appearing to run away from the Beehive – that is, it’s moving westward against the background of stars. Then, just before mid-month it appears to stand still for a couple of days as it reverses direction and starts to come back towards the Beehive (eastward) as if tugged by an invisible cord. In April it will skip right by, missing the Beehive by less than a degree and passing between the Northern Ass and the Southern Ass.

Keep in mind that all this happens over a period of days and weeks, and to see it you need to carefully chart the position of Mars against the background of stars on several nights. This sort of exercise helps you appreciate great observers who charted the heavens before the invention of the telescope. It also helps you understand how puzzled early observers were by the apparent behavior of Mars and why this had them scratching their heads for centuries trying to make sense of these movements in a universe where Earth was at the center of everything. During any given night, of course, everything appears to move westward because of the rotation of the Earth. The movement we’re interested in here is the revolution of Earth and Mars around the Sun.

It’s much easier today – with a sun-centered solar system – to understand why Mars first appears to move in one direction, then the other. This is caused simply by Earth overtaking Mars as the two planets orbit the Sun at different distances and speeds. Here’s where the planets are in mid-March, courtesy of John Walker’s “Solar System Live” online orrery.

Click image for larger view.

See the Zodiacal Light

Finally, don’t forget to look for the zodiacal light this month – especially if you missed it last month.

You don’t need a totally clear horizon to see the zodiacal light, or binoculars, but you do need total darkness and that means little-to-no light pollution. I feel I have a good shot at it from my favorite ocean-front observing point where I have a clear horizon to the west with no cities to create light domes there. Moonless evenings in February, March, and April – and mornings in September and October – are the best time for folks at mid-northern latitudes to look for this subtle phenomena. In March 2010 that means to look about 80 minutes after sunset on a clear night between March 1 and March 15.

For more detailed information on this, see the February posting here.

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