Posts Tagged ‘Double Stars’

Binoculars set up in Observing Shelter awaiting darkness for testing with doubles - and really testing me more than the binoculars. Unitron is there to check seeing conditions and acts as control of sorts - so to the Sparrow Hawk. (Click image for larger view.)

Until the past week I have never seen really sharp stars in binoculars – and what’s more, I assumed that was normal – that what I wasn’t seeing, others were not seeing.


Maybe decades worth of wrong. How many decades?  I’m not sure simply because it’s been relatively recently that I made a serious attempt to see double stars with binoculars and splitting close doubles is the most demanding resolution task of both the instrument and the observer.

From my experience I’ve developed some basic guidelines for splitting doubles with binoculars.  They are:

1. Wear your glasses if you have astigmatism – otherwise do without

2. Sit down – or better, lie back in a lawn chair – you must be comfortable

3. Hold the binoculars steady – even 7X50s will benefit from being on a tripod, or parallelogram mount unless, of course, they are image stabilized types

4. Focus carefully – very carefully –  first the left eye with center focus, then do the diopter adjustment for the right eye while keeping the left eye closed

5. Spend time on target – Look for at least one solid minute – don’t expect instant success.

6. Relax your eyes – let them focus at a distance and get used to it

7. And if all else fails, maybe you have a problem similar to mine – back off from the eyepieces an inch or two, move your head about some – find the correct head position – the one that works and yields sharp stars.

What follows is all about my own special case of “if all else fails” – because believe me, points one through six didn’t make a difference for me until I could settle the issue of point 7 and right now I’m not sure how many others have a similar problem, but I think it’s relatively few.

OK – the point is, I have been happily using binoculars for years without realizing I wasn’t getting the most out of these instruments – not even close to the most. Oh, I’ve seen galaxies out to  50 million light years or more – and I’ve gotten all sorts of expansive views of star clusters and nebulae. But I suspect what I discovered a few days ago may actually enhance  viewing of those objects as well.  What did I discover? That binoculars can, indeed, deliver “refractor-like” images of double stars. Let me be as clear as I can about this.

Double stars should look like the stars in the images to the right. That is, they should look like nice round discs with clean edges. Now any star that is low in the sky is  likely to throw out spikes of light, change colors, and dance about in any instrument just because in that instance you are looking through an awful lot of moving air.

But, if they are overhead or roughy 45 degrees or higher – and the air is average steady, then you should see nice sharp images when your instrument – binocular or telescope – is properly focused.

I do with telescopes – I don’t with binoculars – or didn’t up until recently and still don’t unless I am especially careful.  Is this my special problem? It may be. I have evidence there are some others who share it, but I suspect most people see the sharp stars they should, assuming their binoculars are held very steady – or are of the image stabilized variety – and they have been focused well.

Now let me emphasize that telescopes give me no problem – I can always see sharp, clean images with telescopes when seeing conditions are good. And while I am most likely to see the best images of doubles with either a long focal length refractor, or an apocromatic refractor, I get good, clean star images with any well-adjusted telescope of any design. Not so with binoculars. There the images have been consistently poor for me and I’m still not sure why. but lately I’ve come to suspect that my head simply isn’t screwed on straight – something critics have been telling me for years 😉

Determining what to expect with binoculars – that is, which doubles will split with binoculars  –  is much different than with telescopes. Double star fans know that all doubles aren’t created equal – and that the main problem is how far apart they are in angular measure – usually stated in seconds of arc.  A typical binocular has a field of view of between 2 and 8 degrees depending on how powerful it is. A typical binocular double is separated by less than one minute of arc. So when we are talking about stars separated by, say 30 seconds of arc, we’re talking about a distance that is just 1/120th of a degree. If your binoculars show a six degree field, then this pair of stars is taking up  about 1/700th of that field of view. Darned little.

So you also typically put the pair of stars in the middle of your field of view and the middle of the field of view is where even poor quality binoculars tend to perform quite well. Stars half way out to the edges may start to deform and stretch, but in the center they are sharp.  That’s why I say – and my experience confirms – that quite inexpensive binoculars can perform reasonably well when splitting doubles.

That is the first piece of big news I pulled out of my recent Eureka Moment.

The second was a handy rule of thumb I stumbled across when researching this subject trying to figure out what the heck was wrong with me. Telescope resolution – or expectations of resolution – are typically guided by something called the Dawes Limit which is entirely dependent upon the size of the objective  – a bigger objective creates smaller star images (in terms of angular size)  and will thus split stars that are closer together – it’s as simple as that. Now double star observers no it’s not really that simple – that frequently when the pair of stars have one that is much dimmer than the other, this rule crumbles because the dimmer star gets lost in the glare of the brighter one.

But if we are talking about stars that are within a couple of magnitudes of one another in brightness, the Dawes limit is a good starting point for determining how close stars can be and still be split.  The problem is, this rule assumes you are using fairly high magnification – say 30 times your objective diameter in inches. With binoculars you are almost always using much lower magnification. For example, my 10X30 image stabilized binoculars deliver only about eight times the objective diameter in inches. And my 25X100 binoculars have a power just four times the objective diameter in inches.

But Gary Seronik, in his small book “Binocular Highlights” suggests another rule of thumb that applies to binoculars – simply divide the power of your binoculars into 300. The answer is the separation, in seconds of arc, that those binoculars should be able to split. Thus my 10X30 binoculars – or 10X50 – should be able to split two stars that are separated by 30 seconds of arc. Albireo, a very popular double, is separated by 34 seconds of arc, so the 10X glasses should split it. My 25X100 should be able to split  stars that are 12 seconds of arc apart – that means the very popular double Mizar – which is separated by about 14 seconds – should split in the 25X binocular – and, indeed, it does. However, my 20X glasses will probably have problems with it  – 300/20=15 – and they do, though I have been able to split Mizar with those glasses, it’s difficult. So I think this is an excellent – though rough – guide. (The Dawes limit on those 25X100 binoculars, btw, is  barely a second  of arc – but that is a totally unrealistic expectation for binocular performance. Dawes limit = 4.56 Arc Seconds / Objective Diameter (inches) so 4.56/4 = 1.14. In fact, it is rare for a telescope to achieve this resolution on a double, but something like 1.8″ of arc is a reasonable expectation for a 4-inch t eleescope.)

But these numbers have not mattered much to me when using binoculars. I have only split the widest doubles. So, for example, over the years I really needed 15X binoculars to get a good, obvious split of the Dragon’s Eyes – Nu Draconis – a charming pair of 5th magnitude stars a wide 60 seconds of arc apart. Now, the new me finds them simple with just 10X30 binoculars.  Fifteen power glasses should, by this rule, be able to split stars just 20 seconds apart. The Dragon’s eyes should fall to binoculars as low as five power!  What’s more, in the past when I split this pair I didn’t get the kind of clean, “bullet hole”, stars shown in the image – I got dancing stars – bloated, jiggly stars throwing out spokes of light. It’s just that the 15 power binoculars – and the wide split – made it possible for me to see this pair as  two stars – and I assumed everyone was seeing the same thing.

But I was puzzled how observers I respect and admire like Seronik and Ed Zarenski, to mention just two, routinely split stars that were far, far closer together and instead of bragging about their amazing eyes and observing skills, seemed to think that others could routinely do the same. I know I couldn’t.

It must be my eyes. They must have problems I’m not aware of. That was my first train of thought and I’ve been pursuing that one for the better part of a year – without staisfaction. And a recent trip to the eye doctor confirms my practical experience – there’s nothing seriously wrong with my eyes. In fact, I have what the doctor describes as a “slight astigmatism” – so slight that they say that if I get corrective glasses I will barely notice the difference – and though this doctor worked with folks who sold glasses, she didn’t recommend them for me. (I ordered them anyway – there was  a special on where they’ll cost just $50 and this is something i have to see for myself because this whole business is driving me more than a little crazy.)

The Breakthrough

My breakthough came on a morning when I had decided to test five different binoculars –  10X30IS Canons, 15X70 Celestron Skymasters, 20X60 Pentax, 20X80 Celestrons,  and 25X100 Zhummels.  With the exception of the image stabilized Canons, all would be tested mounted on one of two parallogram mounts. The largest of these mounts was on a pier and really too tall for me to use sitting down, so I was using that one standing.  As a way to check the seeing and to make sure I could actually split these particular stars at low power, I had two small refractors set up as well – a 60mm Unitron using a 40mm Kellner eyepiece for roughly 24X and a 50mm Stellarvue Sparrow Hawk that was a lot like a single binocular in that it used a prism diagonal and was of very short focal ratio – F4.1. I used a 20mm eyepiece in this to get 10X, so it was, in many ways, a good match for the Canon 10X30IS.

My targets were the doubles Albireo (34.4″), Zeta  Lyra (44″), Nu Draconis -Dragon’s Eyes–  (62″), and Mizar (14.3″) – all were at a good altitude on this spring morning.

Initial tests

And the notes from my initial test showed nothing went particularly well at first.  This was the old me.

Actually, I started in the early evening with Mintaka – a wide  split at 52.8″ of arc that should be easy with all the binoculars I was testing, except there also is quite a difference in magnitude –  2.4, 6.8. That 4.5 magnitude difference makes Mintaka a bit of a challenge.  But the 25X100s showed it well. The 20X80s gave me a good look, though not quite as good as the larger binoculars. Actually, the best view came with the 20X60s – not sure why, but this is the old me talking.  I’m seeing a split, but the primary is shooting fire. The 10X30IS gave me an occasional glimpse.  The best view came with the Unitron with the 40mm Kellner, so this was roughly comparable to the 20X60 binoculars, but the star images were much better. I assumed that was because it was a long focal length refractor – and that probably was part of the reason, but as I later learned, didn’t account for all the difference.

The point here is that even the old me could split some doubles – just not nearly as well as I later learned was possible.

I moved on to the much more challenging Mizar. The 10X30IS couldn’t split it – no surprise. The separation is too little for those binoculars. Here I drew a quick sketch of what I saw with the 20X60s because the stars were so bloated and dancing so much I couldn’t be sure I was seeing a split, but I thought I was.  When I checked with the 60mmUnitron I was sure – the binocular view was correct – but, there was absolutely no comparing the two views. The Unitron – at roughly the same power- was far, far cleaner than the binoculars. (Remember, at 20X you should barely be able to split  Mizar – the formula says 15″ is  the minimum separation. Mizar is 14.3″ – though the stars are fairly close in magnitude –  2.2    and  3.9.) The 25X100 gave me a certain split, but certainly NOT “refractor-like” stars.

But something strange was starting to happen. As I maneuverd the binoculars on the parallelogram mounts they were sometimes a few inches from my eyes and once in a while I got a glimpse of sharp stars such as I saw in the Unitron. This first happened with the 20X80 Celestrons and it came when I seemed to bend my head back and literally look down my nose from an inch or two behind the eyepieces. I was tired. I was getting cold. And I really didn’t know what was going on, so I went in with the intention of getting four hours sleep and trying again when I was refreshed.

Morning session

Field notes on Albireo - at last, a clear view.

Nothing comes easily to me – especially in terms of binoculars. I wrestle with mounts, I fiddle endlessly with focus, and mostly I have ended end up seeing something like this:

I have a sense of two stars here, of course, but theimages are dancing, the colors swapping sides, and sometimes I think I see the secondary in one place, sometimes in another.

When I should see – and now do see –  this:

What a delight! This is what I'm used to seeing with a telescope and now - with more and more consistency and less and less hassle, can see with binoculars.

In one sense the change was nearly instantaneous – that is, I would go from a terrible image to a perfect one – no inbetween.  But it only happened after a lot of work and a lot of false steps.

What made me put in the extra effort was I justc ouldn’t reconcile the diffferent experience of using two very nice instruments on Albireo. The first was the Stellarvue Sparrow Hawk aka Little Rascal. This is a 50mm finder, essentially, but  it takes standard eyepieces and is easy to focus. But like a binocular it has a very short focal ratio – F4.1 – and it uses a prism to deliver an erect image. And as my notes show, when I pointed it at Albireo on this particular morning with a 20mm eyepiece (10X) I got a “clean and delicate” split just as I would expect with any telescope – though this wasn’t any telescope. this was essentially half a binocular.

Then when I switched to the 10X30IS Canon’s I was back in Blursville with dancing stars.  And then I started to notice something. I noticed it with the large, mounted binos – the 25X100 Zhummel and the 20X60 Pentax, and 20X80 Celestrons. If I backed my eye way off – I’m talking two or three inches from the eyepieces – and tilted my head so I was in effect looking down my nose  there were long moments when the two stars snapped into sharp focus. Crazy? I’m not sure. When Ibrought this up in a Cloudy Nights discussion forum a few people came forward to talk of similar experiences – but on a few.

Believe me , my heart was racing. I have looked at countless double with binoculars and I had never seen them like this.  This was a real breakthrough and I quickly skipped about from Albireo to Zeta Lyre, to the Dragon’s Eyes and then to Mizar. With these kargerf binoculars everything was great – really great with the bright image sof the 25X100,

I couldn’t believe my luck. I hadn’t even brought out the 10X30IS for this session because I had about given up on them. Twilight was starting to grow brighter in the east. I quickly went back to the house, got the 10X30IS, and voila! There was a perfect Albireo – a yellow star with a scrumptious blue pinpoint right next to it.  I simply couldn’t believe it.  It was every bit as good as I had seen in the tiny Sparrow Hawk refractor.  The only question that remains is why the heck did it take me half a century of observing to discover this?

Well, not the only question. Since this breakthrough I have had three more sessions under the stars and I have expanded the variety of stars I’m looking at to include 16 & 17 Draocnis, Regulus, and Psi Draconis.  I have had my eyes examined by a professional and asked her for ane xplanation – why the heck do I have to look down my nose at doubles? And I have discussed it in online forums and with Larry Patriarcha, the guy who makes and sells the best parallelogram mounts  I know of.  Allt hese people had ideas, but no really firm answers.

But here’s the rub. This is getting easier and easier for me to do – that’s good news, but doesn’t solve the puzzle. I am finding with practice I now achieve this state of double star nirvana without half trying. But it still is easiest to reach if I back off form the eypieces, then, once i get it, approach them slowly being careful to maintain my head position.

So I think it does have something to do with head position – after all, with binoculars you look up – with many telescopes using diagonals you look down.  And it may have some tiny thing to do with astigmatism, and it may have to do with stressing my eye muscles by tiltilting my head back and looking down my nose. But two things are clear to me – first, most observers don’t seem to experience this problem. Second, I don’t understand fully why I do, nor do I understand fully the solution because the ground rules seem to be slipping out from under me. There definitely is a groove and I find it easier and easier to get in it. And believe me, I’m not complaining. This opens up a whole new area of especially enjoyable observing for me.

Doubles I love. I always have found a magic in seeing two perect little globes next to one another.  But now I can see them with both eyes open and while leaning back in a comfortable lawn chair and looking up at the sky – and that, for me, really is double star nirvana.



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I was real pleased when I found the SV80S Lomo perfectly fit the saddle that was on a Celestron – made in China – FirstScope 80 equatorial mount that seemed to be pretty solidly built.

However, before I went out to  observe I did notice one major flaw with  that mount – the slow motion cables attached only to one side of the mount – one on one side and one on the other! What were they thinking? That would be a problem, though the mount seemed to move so smoothly I wasn’t sure I would need the  cables much.

I put the scope out on the rear deck with all related gear as the sun set. I returned to the house and napped in a darkened room through twilight so my eyes would be dark adapted and I could take advantage of the hour or so of dark skies before moon rise.


I spent the next twenty minutes trying to make a single adjustment – the one where you set the latitude. I was doing this by aiming at Polaris and no way could I center it. There was significant play in this motion and every time I tried to tighten it up – not easy since  there is no stop on this mount, so you have to tighten real tight – every time I did this it would move and Polaris would end up being off by at least a full degree. I usually don’t worry too much about that, but the play in the mount bothered me and I wanted to get it right. I couldn’t. I tried over and over again, trying to second guess it by going past the point where I wanted it to stop. I finally gave up and decided to get the 76mm Tasco out of the telescope shed. That meant a long walk with a heavy scope and mount in the dark, plus more set up time, but at least I knew that scope would work, though the mount has a flaw in the RA motion.


After aligning it with reasonable success on  Polaris I decided to hunt down Mu Draconis for another look. (Polaris and companion had shown nicely indicating both decent seeing and transparency.)  But first I thought I should reposition the tripod and then swing the whole head on the azimuth bearing. Uh oh. I could barely get it to move. Well, maybe it wouldn’t matter. I pointed the scope towards Mu, high overhead. Ooops. It hit the tripod leg. Have to move the tripod and adjust that azimuth setting. What the heck is wrong? It’s taking all my strength to barely budge it!

Maybe the scope isn’t quite level and it’s binding? Yeah. that looks like the problem. So I go to adjust the offending tripod leg and the bottom half falls out on the deck and since these legs are round, it rolls away from me – leaving me  trying to act as the third tripod leg while I grope in the dark for the stray limb. That comedy of errors came to a successful conclusion and I got the tripod adjusted so the head was level – but I still needed all my strength to move it in azimuth just a little.

Frustrated, I look quickly for  Mu and with luck, find it right away. Not only that, but it splits beautifully – easier and better than it had the other night. But now the scope is hitting the tripod leg and I can’t follow it as it drifts out of view. That’s it. I’ve had it with equatorial mounts for the night. I want to see if I can split Mu with a 60mm anyway. What I need is that nice, simple, light weight Unitron 114 alt-az.

So it’s back to the telescope shed in the dark and this time I carry the Unitron, fully assembled, back to the deck.  It’s so light you can do it with one hand. This is surely the way to go.


The moon is already starting to rise, but that’s OK – the night is still clear. The  altitude slow motion has run it’s distance, so I have to back it way off. I have trouble getting the altitude lock at just the right tension. The scope swings wildly. I don’t remember that being a problem before. But not insurmountable. It is frustrating though. The azimuth lock also is giving me woes. I must be sending bad vibes to it. But after fooling around with a wide field eyepiece and not finding Mu I’m getting frustrated. I finally turn to the dinky little finder on the Unitron which is positioned so it’s easier to use than most when the scope is pointed near vertical. Bingo. I find Mu with it. Great!

But wait – I can’t focus. I push in the draw tube and it keeps losing focus. What the heck is going on?  The tightening clamp doesn’t seem to be holding. The weight of the Unihex and 1.25-inch eyepiece seems too much when pointed high up.  So I remove the Unihex and go in the lighted house – the hell with night vision. A gibbous moon is already high enough to put that out of play. I look in the closet in the basement and find the other tube you can use with a single eyepiece. I steal the  diagonal from the 76mm Tasco. Great. I’m in business. There’s Mu and I’m able to split it with the 60mm. That’s enough success to bring my mood back to an even keel.

But it’s all I can do to see the companion of Polaris with this scope – even when I first set it up with the moon very low.  And while the split of Mu is technically satisfying, it’s a borderline thing that doesn’t leave me feeling real good. I’m not that thrilled with pushing a scope to it’s edge. I want a more satisfying view of something.  And while I’m getting the hang of the correct tension of the lock knobs on the two axis, I’m finding it a pain. What I really need to do is return to the SV80S Lomo. It is a real nice scope and if I put it on a modern alt-az mount like the Voyager I’ll be happy. Should be easy to do.


First, this means I have to put the clam shell back on the  SV80. The clamshell has two entirely different screws – one short that needs to be turned with a hex wrench – and one long with a knob on the end for hand tightening. I assembled it once, while sitting on the couch, and it doesn’t seem right. The  knob  seems as tight as it can go, but the scope is still slipping in the  clam shell. I back off of the knob – and the knob comes off the screw, leaving the long screw in place with no way to loosen it. Is it cross-threaded? I’m worried, but I get a pair of vise-grip pliers and gingerly clamp down on the screw, hoping I’m not damaging the threads. I loosen it.  Good. I reverse the screws – though I don’t see any reason why this should make a difference. I return the knob to its screw and am able to tighten it so the scope doesn’t move.

OK – now to the shed where the Voyager mount is  in pieces – the head in one place and the tripod in another with an old parallelogram mount on it. No matter. I’m going to make something work right tonight! But there’s no way I can lift the p-gram mount off its post. It sometimes sticks, but this is ridiculous. Again I’m using all my strength and it won’t come off. So once more I am fumbling in the dark – this time with a wrench trying to undo the post. I know this isn’t a real good idea and I’m right. i finally get it undone and sure enough, I jam  two or three fingers between the bars of the the p-gram forced together by the counterweight. This can happen with this mount, I thought of it in advance – but I didn’t think eenough. So I’m sitting there on the floor of the shed in pain until I finally extricate my fingers!


I get the Voyager head onto the tripod and the Voyager is read to do its thing.

RIGHT! Yes, this operation went right. The Voyager/SV80 combo proves to be so good I return to the shed for the eyepiece tray that I had custom made for the Voyager. It goes on correctly. Nice. The scope is on, the eyepiece tray is on, and I have a sweet split of  the double double in the SV80S Lomo – but not quite as good as I think it should be. Some clouds are moving in as well. Still – I’m starting to wonder if the TV Plossls just aren’t the right eyepieces for this very fast scope?

I go get my collection of Naglers. Return to Mu. Yep! The Naglers do a better job than the Plossls. A little more contrast and they are sharp to the edges – the Plossls weren’t. What’s more, the best views come from the Nagler 6-3mm zoom. This is a wonderful eyepiece. It works well with the long focal length scopes and well with the short focal ratio scope. Amazing. If I keep using this scope I may get the 4-2 Nagler zoom!

My cleanest, most satisfying split of Mu comes with the zoom at the 4mm click stop – 120X, Nice! My spirits have moved over to the positive side  of the register. What’s more, an old favorite, Iota Cassiopeia, is above my tree line now. I go for it. Wow! Beautiful – just beautiful.  With the 6mm zoom a pin prick of light appears cleanly – widely – separated form the primary, Go down to 5mm and the the closer – brighter – star is separated from the primary now. At 3mm setting Iota Cass becomes the precious gem that it is.

This is what it should be like. And the Voyager mount is absolutely smooth and provides no frustrations. All works as it should. But the clouds are getting pretty thick now.

So I do a quick look at the moon with the zoom still in and cranked up. Wow! 160X never looked so good. And I quickly reposition the scope so I can get past a tree and see Jupiter. Very nice. No South Equatorial Band yet, though some hint of it.

I got a lot of stuff to put away, but I have at last found a combo of scope and mount that will move easily in and out of the library to the deck for quick set-up and fun star-splitting – plus a lot of other exploring.  Oh – and I can use the 30mm Clearvue with this scope to get a 5 degree fov and so I don’t need a finder at all.

And did I mention that’s what I used to find the third set of Dragon’s eyes? 16 and 17 Dracomis? Well it was and it worked like a charm.  Yes!

Like Shakespeare, I now need one of those famous quotes to sum things up. How about “all’s well that ends well?” At least for this night. 😉

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Boy, this cloudy weather continues ad nauseum, but there was a little break yesterday and it did come just as it began to get seriously dark, so for a couple hours I got to share some quality time with old friends.  The seeing was very good – the transparency, marginally good. But I turned the 120mm refractor immediately to the double-double and with the 5mm Nagler (180x)  had a beautiful, clean, classic split. I just stared. The sight was familiar, but I kept trying to get the numbers straight.

See, between each pair of stars there’s something in the order of 150 astronomical units. That’s roughly 20 light hours. And between the two pairs there’s a much larger gap – variously  stated as two tenths or a quarter of a light year. I’ll accept two tenths. That’s 1,752 light hours. That meant the gap between the two pairs was nearly 900 times as much as the gap between the two stars that make up a pair. It just didn’t seem that much, though,  and I guess if I had been more scientific about it I would have gotten out the reticle eyepiece and tried to measure it.  Maybe I’ll do that some night. But then, if I did so would it mean anything? I tend to assume we’re looking at this system from above or below  – I forget that these pairs of stars are slowly – very slowly – orbiting one another and where they are in that orbit and how that orbit is oriented to us could make them appear closer together than they really are.

All of which is pretty idle speculation on my part, but did move be a bit closer to appreciating the complex system I was seeing.

I wandered on over to M57 for a peek, but as I said, the transparency wasn’t that great – just very steady skies. I decided that I needed to find my way to  a couple objects in Cygnus I’ve never spent much time looking at before.  The first is a binocular triple – Omicron Cygni. This should be a fun challenge for a good night at Allens Pond this summer. Locating the brightest star is pretty easy – it’s fourth magnitude and is in – or near – what I think of as the western wing of the swan.  What I didn’t know until I checked Jim Kaler’s Web site just now was that in viewing these I managed to miss a carbon star nearby (U Cygni). Dang! And the mental image I retain tells me I saw it and didn’t pay close attention, but I have an overall impression of a very red star in the field.  I was using the 32mm Plossl which gives me a comfortable field of more than 1.5 degrees. Didn’t have any appropriate binoculars handy, but judging from the view in the finder, it should be easy to spot two of these stars while the third will be difficult.  And I’ll have to remember to look for U Cygni next time I have a chance.


My next step was to drop a trail of bread crumbs on the way to 61 Cygni. This fifth magnitude star is off the eastern wing of Cygnus and is the fourth closest star in our night sky and the first to have it’s distance from us measured (11 light years) more than 150 years ago. It’s sometimes called Bessel’s Star or Piazzi’s Flying Star – Bessel’s Star because he first measured its distance in 1838 and Piazzi’s Flying Star because he noted how fast it appeared to be moving (partly because it is so close to us) about a half century before Bessel made his measurement. Me – all I wanted was an easy way to find it in a  kind of busy area of the Milky Way and I discovered that it was conveniently at the apex of rwo bright triangles easy enough to pick out in wide field binoculars.  (See the chart to the left  modified from Starry Nights software.)

Funny – the North American Nebulae has always eluded me, yet for some reason with the 120mm on a night with transparency poor, I felt I could see it fairly easily using the 32mm eyepiece in the 120mm refractor. There was a fairly obvious change in background brightness where it should be. So I need to revisit this with that instrument on a better night.

By this time I was getting tired, however, and the clouds were moving in, so I made one final excursion. This time I swung to the western sky where Izar was still very high and in the steady air, very easy to split  – though I really had to crank up the power to get a comfortable view. I used the 2.5mm Nagler giving 360x – well above 60x per inch – but it worked fine which said good things about the quality of the scope, the quality of the eyepiece, and the quality of the night.

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No kidding. (Yeah, I think all those apostrophes make sense 😉

One of my favorite destinations in the summer skies – or early mornng skies these March days – is the well-known Double Double. This multiple star is not only beautiful and charming, but is frequently a bit of a challenge and seeing what power it takes to split it cleanly is a good indicator of how good the seeing is at that moment.

What I didn’t know after all these years was that the Double Double has  an easy alternative – sort of a Double Double with training wheels attached – for those who want a warm-up exercise – or just a fun side trip. It’s neither as charming nor demanding as the Double Double, and it is not a true binary system where all the stars are related and in one another’s gravity field. But – it’s got it’s own charm and it is easy. I learned about it from “Turn Left at Orion,” the great little observer’s guide from Guy Consolmagno and Dan Davis.  I was checking the distance to the Double Double stars before going out (200 light years) and saw under “also in the neighborhood” directions for finding the Double Double’s Double.

Finding Iota.

Finding Iota.

I won’t give all the details. Essentially you go to Iota Lyrae, a 5th magnitude star that’s easy to star hop to from Vega. (It’s barely visible to the naked eye here on the best nights, but bright in the finder.)  See chart above.

Moving Iota to the top right of this 2-degree field I was easily able to see the pair of 7th magnitude stars that make up the Double Double's Double.

Moving Iota to the top right of this 2-degree field I was easily able to see the pair of 7th magnitude stars that make up the Double Double's Double.

A degree and a half due south of Iota (see chart above)  are two seventh magnitude stars – a nice, wide pair like the  two primary  stars of the Double Double.  (Actually, these two are about three times as far apart as the two primary stars in the Double Double.) They are  Struve 2470 and 2474. The first one has  an 8.4 magnitude companion a generous 14 seconds west of it. The second has an 8.1 magnitude companion 16 seconds west of it. (To put those distances into perspective, the separation of the close pairs in the Double Double are 2.8 and 2.3 seconds – much more challenging.)

This was easy to split with the 80mm Eon and 13mm Nagler eyepiece yielding about 46X. (The same scope split the Double Double this morning, but needed 171X to do it and gave the cleanest split at 240X – a magnification I was surprised the little scope handled so well.)  I’m sure the wider Double Double’s Double will split with low  power and a smaller scope. It will be fun to check out in the “Little Rascal” – if it ever arrives. (Seems they sent it to the worng lace, so maybe I’ll get it next week.)

So – I find this all a little tongue twisting, but fun, and a good exercise in star hopping and splitting.

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Summer’s other triangle – that’s what Gary Seronix calls the familiar triangular pattern around Vega. I’d never thought too much about it until poised in the snow yesterday about 6 am, I swept the sky in that general direction with the 66mm AT at low power and stumbled across Zeta Lyra – it felt like a new discovery, though I must have seen it a thousand times.

See. a few minutes earlier I had been looking at Nu Draconis. Now this is a  wonderful double for binoculars, or low powered, small telescopes like I was using.  Nu is relatively easy to find because it’s the faintest star of the five that make up the “home plate” type shape of the head of Draco. (Well, OK, to make a “home plate” you have to borrow a fifth star from Herculis. Draco’s head is usually shown as a four-sided, irregular polygon.) What I love about Nu is that this is a nearly perfect pair of 5th magnitude stars, separated by 43 seconds of arc and barely detectable in ordinary binoculars as double. Go to something like my image-stabilized 12X36mm Canon and it’s pretty easy – but turn a small scope on it like the 66mm and it is a real delight. There’s something hypnotic in seeing two Suns of almost identical color and brightness this close to one another.  I fiddled with my small, portable stool and eyepiece position so I could sit their and really soak this in. While I was doing this, we kept turning towards our own star, of course, and to the naked eye Nu and it’s companion stars that form Draco’s head began to vanish in the twilight glow.

It was a balmy 16 degrees, though, with no wind, so I sat and enjoyed.  Part of me was fiddling with the telescope – trying to get it to work better – well, not the scope, but the mount. It is the light weight version of Vixen’s popular Porta Mount and I am not that pleased with it. I really like the Astro-Tech Voyager better, but it’s heavier and so there are trade offs between steadiness, ease of use, and ease of lugging around. It was because of this – and also trying to decide if the little camp stool – which is easy to carry – was a viable choice here as an observing chair, that lead me to scan in the general direction of Vega. That’s when I suddenly swept up another double that looked a lot  like Nu’s twin – only the two stars weren’t identical – I felt there was about a magnitude difference between them – but they seemed to be separated by the same gap as the stars in Nu and I wondered what they were.

A little more sweeping around – then take heel of hand and thump forehead several times. What a dummy! I was looking at Zeta Lyra, a star I’ve seen so many times I couldn’t begin to count them – and yet, I had never paid any attention to it because every time I had seen it I was on my way to the familiar – and spectacular – Double Double – Eta Lyra. This is the problem with having favorites – you tend to ignore some nice things that are in plain sight.  Vega is hard to miss – it’s the fifth brightest star – and the brigtest in the huge  Summer Triangle of Vega, Deneb, and Altair. The images – and captions – below are screen captures from Stellarium and explain the progression from Vega to Zeta Lyra

Vega dominates the tiny constellation, Lyra. In February its high in the East before morning twilight begins. Two dimmer companions form an obvious triangle with Vega.

Vega dominates the tiny constellation, Lyra. In February its high in the East before morning twilight begins. Two dimmer companions form an obvious triangle with Vega.

Binocular will easily show that the fainter star that makes up the bottom left of the triangle is really a closely mnatched pair of stars. (A small telescope will show that each of these is a double - this is Eta Lyra, the "Double Double."

Binocular will easily show that the fainter star that makes up the bottom left of the triangle is really a closely mnatched pair of stars. (A small telescope will show that each of these is a double - this is Eta Lyra, the "Double Double.")

M y smnall telescope clearly reveals that Zeta Lyra is also a double, but this is a real challenge to split cleanly with binoculars because the two stars are of different brightness.

My small telescope clearly reveals that Zeta Lyra is also a double, but this is a real challenge to split cleanly with binoculars because the two stars are of different brightness - 4.3, 5.7.

What I really like here is that all of this illustrates some basic points –

  • While I advocate planning an observing session before going out, there are times when just prowling around, discovering something interesting, then trying to figure out what it is you’ve found is much mroe fun.
  • Switching from naked eye to binoculars to telescopes of different size gives us a whole new perspective on objects. What can be boring in a large telescope can be exciting in a small one – and genuinely better.
  • In his book “Binocular Highlights”  Seronik points out that a simple formula for determining the closest double star you can split with binoculars is to divide the power of your binoculars into 300. That will yield a result in arc seconds and looking at this triangle gives a very quick test of the theory.
  • The other major factor in splitting a double star is the difference in brightness between the two stars – and Nu Draconis and Zeta Lyra illustrate this well, They both have almost the exact same distance between the two stars – 43 arc seconds for Nu and 44 for Zeta Lyra – but Zeta is far harder to split because there is a bout 1.5 magnitudes difference in brightness.

I checked this for myself this morning under far from ideal conditions. My 12X36 IS binoculars should split stars that are 25 arc seconds – or greater – apart. (300/12=25). My 8×42 glasses should split stars with about 38 arc second between them by the same formula. Well, the 12X36IS can split both doubles – but it has real trouble with Zeta.  The 8X42 splits Nu Draconis, but when I try to split Zeta I get a distinct impression that it is more than one star – but not two.  Why? Not because they are too close for this power, but because they are close and the difference in brightness adds to the difficulty. Eta Lyra – the Double Double – is easily split into two compoents by either binocular, but the gap betweent hese two is huge – more than 200 arc seconds.

Bottom line – there’s a beautiful small triangle around Vega – which in itself is a magnificent star – and be sure to explore each of the components with binoculars and/por telescope.

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