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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 January 2014 – Hello Jupiter and Mercury, Goodby Venus

In January 2014 Jupiter rises in the east as the Sun sets, dominating the brilliant Winter Hexagon, and Venus sets shortly after the Sun making it very hard to see after the first week of the month. But Mercury will tease us for a week or so with a brief appearance.

How do you find these planets? They’re hard to miss because they are so bright.

Jupiter

Wait for a couple hours after sunset – by that time it will be  about  three fists (roughly 30 degrees) above the eastern horizon.  It’s in Gemini and at magnitude -2.7 it is far brighter than that brilliant collection of stars we call the Winter Hexagon. Here’s what you should see.

Jupiter in the Winter Hexagon. Click for larger version. (Prepared from Starry Nights Pro screen shot.)

Jupiter in the Winter Hexagon as seen from mid-northern latitudes about two hours after sunset in January, 2014.. Click for larger version. (Prepared from Starry Nights Pro screen shot.)

Click here for a printer-friendly version of this chart

The brightest star of the Winter Hexagon is  Sirius, but Jupiter easily outshines it. Betelgeuse is inside the Hexagon – and yes, Castor and Pollux count as one star for the purpose of this asterism. ( If you counted them as two the “hexagon” would have seven sides!) This is the greatest concentration of very bright stars in our sky and is one of the reasons why we tend to think of winter nights as being clearer than the nights of other seasons.

If you have binoculars and a steady hand, see if you can see any of Jupiter’s four moons. They will be little pinpoints of light near the planet roughly in a line that goes through the planet’s equator. Binoculars will frequently reveal one or two of the four moons that are very easy to spot in any small telescope.

Venus

Venus starts out the month fairly easy to spot very low in the southwest about 30 minutes after Sunset. It is the brightest “star” in the sky, outshone only by the Moon and Sun, and is a bit west of southwest..  BUT . . . you need clear skies and an unobstructed western horizon and with each day Venus gets significantly lower so that by the end of the first week in January I think it will be very difficult to spot from my location at 42 degrees north latitude.

Of course Venus isn’t vanishing. By the end of the month it will be a “morning star,” shining even more brilliantly in the sky just before dawn. It will stay there right through September and by next  winter it will be in the evening sky again.

 Mercury

Mercury always teases, quickly putting in an appearance and just as quickly vanishing. In this case it come son stage at the end of the month. It’s going to be in about the same location as you last saw Venus – that is, a bit west of southwest about 45 minutes after sunset – at that time  should be about 6 degrees above the horizon on January 26, 2014.

It shine at about magnitude -.6 – brighter than nearly any star, but, of course, this will be diminished by twilight. It reaches it’s highest point – about 10 degrees, or one fist – right at the end of the month and should stay visible through the first week or so of February, though it will be lower each night.

Binoculars will be helpful in finding it. Start looking about 30 minutes after sunset. It will get a bit easier each night for the last week in January, then as February begins it will start getting closer to the horizon – and the sun – and thus harder to see each night.

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.

August 2009 – and all the planets have shown up for the party!

That’s the good news – the bad news is the “party” is an all-nighter. That is, if you really want too see all the planets – and maybe little, demoted Pluto as well – you need to start at dusk and stay at your task well into the wee hours of morning.  For Pluto, you will also need a powerful telescope and better charts than I’ll provide here, but the others can all be seen with the naked eye or binoculars.

But what I like about this situation is it makes it easy – even for those of us using nothing but the naked eye, which is really the focus of this web site  – to  see most planets on a single night and to get a sense of how their position in the sky relates to our position in the solar system and where we all are on our annual journey around  the Sun.

Astronomy is always about two realities – the reality we see and the reality we know. The trick is learning to merge these two so that when you see something in the night sky, you are familiar enough with what is really going on that what you see makes perfect sense, given what you know.

orrery_080109

The best example of this is provided by the two major planets this month – Jupiter and Saturn. The chart above shows the reality we know. It shows where all the planets are at the start of August if you could get  above the plane of the solar system and look down at them. Study it. This is from the online orrery at “Solar System Live.” (http://www.fourmilab.ch/solar/)  I drew the bar across it to represents our horizon – the line between night and day –  and the arrows show the direction the bar is moving as night progresses. To the left this shows how, from our perspective, things are setting in the west – and to the right, how they are rising in the east.

Notice that in this view Saturn is near our western horizon and Jupiter near the eastern horizon. That’s the situation right around sunset. But the sky is too bright then for us to see even bright planets. We have to wait about 45 minutes. At that point, Saturn will look like a first magnitude star about 12 degrees above the horizon almost due west – azimuth 266 degrees – in the early part of the month.

Switch to the east and Jupiter is not so shy. It is at magnitude -2.8 (nothing gets brighter than this except Venus, the Moon, and the Sun), but it is still hugging the horizon. Chances are it is too close for you to see. Give it another 45 minutes – 90 minutes after sunset – and it will be about nine degrees above the horizon a bit south of east. For my latitude – 42 degrees north – it will be at azimuth 118. But the exact position isn’t too critical, since it is so bright and there’s nothing in that general vicinity at this time that will compete with it.

This will change slowly as the month goes on – that is, Saturn gets closer to the horizon at sunset each night and Jupiter rises earlier, until on August 14th Jupiter is rising in the east as the Sun is setting in the west.

Did you notice on the solar system view that Mercury is right over there near the western horizon as well? It is, but this happens to be a fairly poor showing for what is always an elusive planet to catch. Sky and Telescope gives this instruction: “Observers near 40° north can look for it 5° above the western horizon a half hour after sunset from August 6 to August 18th.” Yep – and it will be near magnitude “0” – but you will need a very clear western horizon to see it, and I suggest you search for it with binoculars.  Earlier in the month is better than later for both Saturn and Mercury. As the month goes on Saturn not only gets  closer to the horizon, but also closer to Mercury – and this will make  both very difficult to see. By August 17 the two planets are just 3 degrees apart, but then Mercury is only 2 degrees above the horizon and Saturn about 6.

Much easier to find are our two morning planets, Venus and Mars. Both can be spotted, without strain, with the naked eye. But Venus is by far the easiest. It is a brilliant  magnitude -4 – brighter even than Jupiter, which by this time is well over in the southwest, and should be easy to see low in the east northeast by 3:30 am. By the end of the month you’ll have to wait until about 4:30 am for it to be easily seen – but that’s still two and half hours ahead of sunrise.

Mars is a bit more of a problem, though it rises well ahead of Venus. At 3 am August 1 it is a first magnitude “star” about 7 degrees to the north of Aldebaran, also first magnitude,  and both are roughly 15 degrees above the horizon, a bit north of east. Because Aldebaran is a very red star, it will be interesting to compare it with the “red” planet, but it’s best to wait another hour to do this so both are higher in the sky and not as affected by the atmosphere, which tends to make every bright object colorful.

By the end of the month Mars is higher at 3 am, but Aldebaran is higher still. Mars will form an interesting triangle, though, with Aldebaran and another very red star, Betelgeuse. In fact, if you are up at that hour you get a preview of the early winter sky with the bright constellations of Auriga, Taurus, Gemni, and Orion coming into view, and Mars in the middle of them as our chart shows.

Mars early in th emorning at the end of themonth. Click for larger version. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Mars early in th emorning at the end of themonth. Click for larger version. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Returning to the evening sky, this remains a good year to track down Neptune and Uranus with binoculars. Both are relatively easy to find, but offer special challenges.

Notice on the solar system chart how Neptune is roughly in line with Jupiter as we view both from Earth. On August first a careful study of the Jupiter region with binoculars around 10 pm will reveal Neptune at about magnitude 8 and only two degrees to the north (left) – but finding it can be tricky.  Try putting Jupiter in the right-hand edge of your field – or even move your binoculars so Jupiter just drops out of the right hand edge. That way the glare from it won’t interfere with your view.  At that point Neptune should be pretty close to the center of your field of view. There are several stars nearby and both Neptune and Jupiter are changing position as the month goes on. Here’s a chart for August 1.

Neptune and Jupiter at the first of August, 2009. (Clickfor larger view.) (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Neptune and Jupiter at the first of August, 2009. (Clickfor larger view.) (This chart uses a screen shot from Starry Nights software which I have then annotated.)

By the middle of the month, they have drifted a bit farther apart, and there’s a row of sixth magnitude stars in a gentle arc between them. If you compare the first chart and this second one you will see these stars and how the position of the planets change relative to them.

Neptune and Jupiter near the middle of August, 2009. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Neptune and Jupiter near the middle of August, 2009. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

By the end of the month these same stars are closer to Neptune and the gap between Neptune and Jupiter is almost five degrees. That means they both probably fit in the same binocular field, but just barely.

If you look at the horizon line on our solar system chart – especially the eastern one – and note the direction it is moving, then you can see how our view will change during the night. As Jupiter and Neptune get higher we eventually get to a point where Uranus comes into view, then, well after midnight, Mars and Venus put in an appearance.

Uranus is easier to see than Neptune because it’s significantly brighter – about magnitude 6.  We also get a special break this month, for Uranus will form a wide “double star” with 20 Piscium, a star that is just a tad brighter than the planet. But this makes it easy to identify.  Here’s my way to locate it. First, trace out a few asterism in the sky south of east. (The following chart is for 11 pm EDT, August 1, at 40° North – but should serve as a general guide for almost any location.)

This charts helps you locate thegeneral area inw hich to find Uranus. Click forlarger version. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

This charts helps you locate thegeneral area inw hich to find Uranus. Click forlarger version. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Next, you want to zero in on the Circlet of Pisces and an unnamed trapezoid below it.

Tracking down Uranus with binoculars. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Tracking down Uranus with binoculars. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

The Circlet will not fit quite in the typical binocular field of view. The trapezoid should fit and maybe Uranus at the same time – but the way I find Uranus is to find the trapezoid in my binoculars, then move up so that only its top two stars are visible in the bottom of my field of view. Now up and to the right are two almost identical stars – the higher one is Uranus. It is about half a degree above 20 Piscium, a star that is just a tad brighter, though you will be challenged to tell the difference.  (The charts show only those stars you can expect to see with your binoculars – but depending on the binoculars and conditions, you may not see all of these stars.) Uranus is on the brighter side of magnitude 6 and at this point, at least 10 degrees above the horizon. Waiting until later in the night – or later in the month, this will only get easier as Uranus will get higher.  But as the month goes on it will pull away a little from 20 Piscium. By August 30 they are a degree apart and instead of Uranus being directly above 20 Piscium, it will have moved above and to the right – westward.

And Pluto? I wouldn’t try to hunt it down even with my 15-inch telescope.  Although it is relatively high in the south once it gets really dark, it is much too faint to see in anything except large amateur scopes. And to make matters worse, it has lots of competition, for it is above the Teapot in the middle of the Milky Way, and at magnitude 14, just a faint, faint dot among many, many other faint dots. Better to spend your time exploring the Milky Way itself. See: August Guideposts: Asterisms guide you along the Milky Way.

This is the general area within which you can find Pluto this month. But theplanet is faint and buried with the faint stars of the Milky Way.  (This chart uses a screen shot from Starry Nights software.)

This is the general area within which you can find Pluto this month. But theplanet is faint and buried with the faint stars of the Milky Way. (This chart uses a screen shot from Starry Nights software.)

Choosing and using binoculars for astronomy

What binocular should I get to view objects in the night sky? The short answer is almost any binocular will help, but if you’re looking for a one-size fits all answer, get a good 10X50 binocular. Of course, one-size doesn’t fit all, so here’s some background that I hope will help you find the correct answer for you.

Binoculars are an incredible way to extend your reach into astronomy and while I recommend everyone start by observing with the unaided eye, binoculars make a wonderful next step. There are a handful of astronomical objects that are best seen with binoculars and a lot more that become more interesting and beautiful if you point binoculars at them.

Binoculars are essentially a pair of low-power, wide-field telescopes that are easy to carry and easy to use. As with any telescope, their main purpose in astronomy is to gather more light allowing you to see fainter objects. If your naked eye view of the stars ends with stars of magnitude 5, binoculars can extend that view to magnitude 9 or even 10. There are approximately 2,800 stars of magnitude 5 or brighter that can be seen with the naked eye. But use binoculars and that number jumps to roughly a quarter million of magnitude 9 or brighter stars and more than half a million stars at magnitude 10 or brighter. So you see, binoculars make a huge differences!

Binoculars are commonly identified by two numbers representing their power and the diameter of their objective lens. For astronomy, the best all around choice – in my opinion – is 10X50 binoculars. The first number means the binoculars magnify 10 times – which means essentially you instantly cut the distance between you and astronomical object by a factor of 10! The second number refers to the diameter of the objective lens in millimeters.

This last is an indicator of how much light the binoculars gather – and thus how faint the object is that you can see with them. This number is a bit deceptive because what is important is the light gathering area of the lens. Let’s take a look at two simple examples to see how this changes.

To begin with, the eye of an older adult typically opens to about 5 mm.(Yes, the eye of a teenager may open to 7mm or more – but this quickly changes with age in most people.) Let’s assume 5 mm is the norm. This figure means the light gathering area of your eye is roughly 20 square millimeters. A 40 mm binocular lens has a light gathering area of 1256 square millimeters – more than 60 times that of your eye. A 50 mm binocular lens has an area of 1,962 square millimeters – roughly 100 times that of your eye. Notice the big jump between the 40 mm and the 50 mm lens. Area goes up much faster than diameter.

The power number is also important, but only for putting a high end to things. It’s easy to add power to a binocular, but even a person in excellent physical condition can not hold a high-powered binocular steady. In fact, I believe that any binocular above 10X needs to be put on a tripod for a steady view – and that decreases its ease of use tremendously. Frankly, even a 10X binocular can reveal a little more if put on a tripod. I would favor binoculars a bit below 10 power generally, but there’s a catch.

There is no sense bringing more light to your eye than your eye can use. The light from a binocular is focused in a cone known as the exit pupil. Exit pupil – the diameter of this cone as it enters the eye – is easy to determine. Just divide the power into the diameter of the lens. Thus a 10X50 binocular has an exit pupil of 50 divided by 10 which is 5 mm. That 5 mm exit pupil matches the dark-adapted eye of the typical adult and that’s why I recommend this as the limit.

Popular 7X50 binoculars provide an exit pupil of 7 mm. Since this is much larger than the pupil of your dark adapted eye, you actually will see less with these binoculars at night then with a 10X50 pair. The lenses are the same size and they gather the same amount of light – but with the 7X50 binoculars that light is put in such a large cone that nearly half of it misses your eye. Suddenly the 50 mm lens is acting more like a 30 mm lens in terms of the faintest star it shows you!

The last number that is critical is eye relief. This too is in mm and you want something that provides at least 15mm of eye relief. This number simply represents the distance your eye should be from the binocular lens. It becomes especially important for people who wear glasses and only then if you have to wear glasses because of astigmatism. If astigmatism is not the issue, you should simply take your glasses off when using binoculars. Focusing the binoculars will correct your vision. But for convenience sake, some people like to leave their glasses on. With your glasses on you can not get your eyes real close to the binocular eye lens and this may mean that you lose a significant portion of the field of view and light that is gathered. You want binocular designed so that when wearing your glasses you still get the full use of them and this is why you want an eye relief of at least 15 mm.

So does this mean that everyone should purchase 10X50 binoculars for use in astronomy? Absolutely not. Your rule should be this:

Purchase the largest binoculars you can comfortably hold whose exit pupil is lower than 5.

Binoculars get heavy quickly as you turn your head upwards and peer at the sky searching diligently for a star cluster or nebula. And heavy binoculars can just be a pain to carry around all evening.

So, for example, 7X35mm binoculars do not collect nearly as much light as 10X50. But they are still an excellent choice for many people because they are much lighter and because it is easier to hold 7X binoculars steady than 10X ones. Notice that the exit pupil is exactly 5mm – that is 35/7 equals 5. Similarly, 8X40 make an excellent choice.

Don’t get fanatic about these numbers. Any binoculars will help you see more.

Choosing binoculars for astronomy, by the way., doesn’t preclude their use for other activities, such as bird watching. And sometimes their ability to do well in dim light – while critical for astronomy – is also very helpful when looking for a bird or deer in twilight.

Finally, whatever binoculars you choose, do learn how to use them. Most binoculars have a central focusing knob and most people simply hold them up to their eyes and focus them with this knob alone – and this is a mistake.

When you first use a pair of binoculars you should do this:

  1. Aim at a distant object, close your right eye and focus with the central focusing knob using only the left eye and thus the left side of the binocular.
  2. Once focused that way, don’t touch the central focusing knob. Instead, close your left eye and use the diopter adjustment on the right binocular eyepiece (just twist that eyepiece, it turns while the other one doesn’t) to make sure the view through the right side is in perfect focus.
  3. Thereafter you simply use the central focus with both eyes open for any objects you wish to focus on.

It is the second step that is usually ignored – but when you ignore it you are not getting the most out of your binoculars. It’s a bit of a bother, but our two eyes are seldom the same. And binoculars adjusted this way for one observer will not work at their best for another observer. Usually binoculars are a personal item that are used by a single observer. But if someone hands you a pair of binoculars to observe with, you should first adjust them in this two-step process for your vision. Then when you hand them back to their owner, it is polite to remind them that you have changed the diopter adjustment and they will need to change it back.

Of course, they may not know what you are talking about when you say this. I’m amazed at how many people who own binoculars are unaware of this. In that case, you can be helpful and explain it to them.

To sum up:

  • Make sure you’re comfortable with the weight of the binoculars you choose.
  • Get the largest diameter objective lens you can comfortably carry and hold.
  • Don’t exceed 10X magnification for handheld binoculars.
  • Don’t exceed a 5mm exit pupil unless you are young and know your dark adapted eye opens wider than 5mm.
  • If you must wear glasses, make sure the binoculars you choose offer enough eye relief so that wearing glasses does not cut down on your field of view.

A few things to generally avoid:

  • Binoculars with a ruby coatings on their lenses.
  • Zoom binoculars
  • Very wide field binoculars

My personal choice for astronomical observing are 12X36 Canon image stabilized binoculars. If you have been following closely you’ll see this violates the power rule – but only because I’m willing to pay a premium price for a good image stabilization mechanism. before I owned these I had a pair of 15X45 image stabilized binoculars, but I found that while these were excellent astronomy glasses, I frequently did not use them. They were simply too large and bulky for me to want to carry them all the time, or to hold them to my eyes for extended views. So I sold them, sacrificing power and light grasp for a pair that were smaller, but that I use much more often.

And that brings us to the final rule that applies to all astronomical instruments, including telescopes: The instrument that’s right for you is the one you use the most. Don’t get obsessed with the numbers game. Be aware of it, but choose what works for you.

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