• Choose a post by category or constellation

  • Learn the Night Sky

  • Search strategies

    Use the Search box below to find doubles by popular name, RA, or telescope size. For example, a search on "15h" will find all doubles we've reported on that have an RA of 15 hours. A search for "60mm" will find all doubles where we used that size telescope.

24 Comae Berenices – easy split with any scope, but bigger sure helps colors

I “discovered” – well, stumbled upon – 24 Comae Berenice while trolling for galaxies with a 12-inch Dob. That immediately prejudiced my opinion of it – it was beautiful! A spring rival for Albireo. How had I never  seen it before? And why did I  find it so hard to find again?

24 Comae Berenices – Σ1657 – H IV 27 – HIP 61415 – SAO 100159
RA: 12h 35.1m Dec: +18°23′
Mag: 5.11, 6.33  Sep: 20.1″ PA: 270°  (WDS 2012)
Distance:  2631 Light Years
Spectral type: K0, A9

Well, for starters I didn’t know what I was looking at in that first view and I guess I am focused on this region as the happy hunting ground for galaxies so I never seriously thought about doubles here. Should have, though, because there are several. We’ll stick with 24 – aka Σ1657, though. This little gem is between the Virgo Cluster of galaxies and the Coma Berenice cluster of stars, so it’s a prime candidate for stumbling upon – especially if you like just prowling about for galaxies in  this region.  Haas lists it as a “showcase” and  “the Night Sky Observer’s Guide” calls it a “springtime version of Albireo.”  It’s still reasonably accessible in early summer. In fact,  as 24 Comae Berenices heads for the western horizon you can check out the real Albireo in the east. A couple hours after sunset  on the Summer solstice  they are both roughly 40 degrees above their respective horizons when viewed from  mid-northern latitudes.

That said, I thought it would be a piece of cake to find 24 again, but when I looked on different nights  with a 60mm Unitron, a 100mm Skywatcher ED, and  a classic RV-6 Dynascope I found myself spending much more time searching than I expected. Problem is, there are a lot of stars in the 5-7 magnitude range in this region and I ended up developing both a bottom up strategy, and a top down strategy for a star hop and I still can’t tell you which works best. Let me show you what I mean.

Two suggested star hops to 24 Comae Berenices prepared from Starry Nights Pro screen shot. Click image for larger view.

As to colors, I had the primary as yellow going to orange – I settled on “tangerine-in-bright-sunlight”  for the primary and the secondary as “summer-sky-blue” – especially if your summer skies tend towards the murky as mine do right now. But these colors screamed at me when using the light grasp of the 12-inch and they were fine in the 6-inch reflector. But they lost some of their zip in the 4-inch refractor and I was a bit disappointed with the view in the  60mm. All of which makes sense since are eyes need a lot of light to see color and when you look at the numbers, Albireo has a full two magnitudes on this pair.

Speaking of numbers, though, the spectral types of K0, A3 do confirm my color descriptions, making the colors similar to, but a bit more subdued than Albireo – that is the Albireo blue is more intense.. Use those numbers then look at this chart.

The “apparent” column is what we tend to see.

Now using the same chart, look at the colors for the Albireo pair – Spectral type: K3, B0

The 20-second split should be easy in just about any scope – in fact, I think this would make a real nice binocular double, though I haven’t tried that yet.

The colors I saw on the night I made this sketch weren't quite as obvious as when Greg looked at it, but it's a colorful pair nonetheless.   (East & west are reversed here to match the refractor view, click on the sketch for a larger version).

The colors I saw on the night I made this sketch weren’t quite as obvious as when Greg looked at it, but it’s a colorful pair nonetheless. (East & west are reversed here to match the refractor view, click on the sketch for a larger version).

The Polaris (binocular) challenge – a learning exercise for new Splitters and a warm-up exercise for experienced ones

Polaris (Alpha [α] Ursa Minoris) (Σ 93)
MG: 2.0, 9.1  Sep: 18.2″  PA: 232°  (WDS 2009)

You can take this as a challenge, a lesson in splitting, or a warm-up exercise to use any time you feel like it  before moving on to something new.  For Northern Hemisphere observers Polaris is perfect in this respect because it is available every night, all night,  and stands virtually still. What’s more, it is not only a good challenge for binoculars, but also for any small scope.

Conclusions first

For me it has been all these things, but most importantly it has been a learning experience. I won’t keep you waiting – here’s what I have learned by taking the Polaris challenge:

  • I can easily split Polaris at 30X
  • I can intermittently split Polaris with 20X80 mounted binoculars in average conditions
  • All the numbers we use  – I use – are approximations, so don’t get anal retentive about them unless you have done a thorough, optical analysis of your equipment. (Something that is beyond my knowledge and patience.)
  • My binoculars say “20X80” on them. The effective objectives are really closer to 72mm, not 80mm –  that much I can measure.
  • I have  developed a simple, sure-fire way to always know where Polaris B should be
  • I have found that splitting nearby Mizar, with stars much more closely matched, but separated by 14 seconds instead of 18 seconds – is a great warm-up to splitting Polaris.
  • All the other general rules for splitting apply in spades –
    • be comfortable
    • be well rested
    • be fully dark adapted
    • focus with extreme care
    • position your head carefully in line with the eye lenses
    • spend time on target
      • look for at least a solid minute at a time

And now the details – how I got there from where I was

I start as a 70-year-old star splitter who has never sought the challenges John routinely takes on, but who has over half a century split more double stars more times than I care to remember and at the top of my list of stars frequently split is Polaris. I do a lot of outreach and I almost always include it in the show, usually using at least a six-inch scope so my  visitors have no trouble seeing that little faint dot next to the second magnitude primary and reminding them then that if our Sun were placed at the distance of Polaris it would be a bit fainter than the  secondary – Polaris B.

Recently I finally made a breakthrough splitting doubles with binoculars – something that was a real eye opener for me – and I was hooked on the kind of delicate images – and  elegant splits you get at low power – or any time your splitting takes you into the realm of the improbable. So I had to see if I could split Polaris with binoculars. And I thought I did on my first try with 25X100 Zhumells – only when I checked our own web site to remind myself  of the position angle  (pa) of Polaris I found that my supposed split was simply wrong – way wrong – 180 degrees wrong!  Now that is embarrassing to an experienced star splitter – but it came because I was really under estimating what I should see and because I didn’t have an easy way to know where to look for Polaris B.

Knowing where to look is a special case – and I have since seen writings where experienced observers screw it  up – because Polaris is rotating around the North Celestial Pole just like every other star – so Polaris B will, in the course of 24 hours, appear to rotate about Polaris. All this means is to use the Position Angle of 232 degrees for Polaris you have to apply the same two rules that you apply to any star:

  • west is the direction the stars appear to be moving
  • north is the direction from the primary towards Polaris

Whoops! Can’t use that second one here because we’re looking at Polaris. So which direction is true Celestiual North when you look at Polaris? To answer that find the crude asterism known as the “engagement ring” – those  stars will always be to the south of Polaris and the position angle of the brightest star in the ring is darned close to the position angle of Polaris B – all of which should become clear as you study this chart.

Low power finder chart for Polaris B showing field for 20X80 binoculars. Polaris B is at almost the same pa as the star marked 64 - brightest star in "Engagement Ring" asterism. Click for a larger version. Developed from Starry Nights Pro screen shot.

The preceding chart serves as a guide in two keys ways – first, use it to know where to look for Polaris B.  The secondary is, of course, much closer to Polaris than any of the stars shown, but with a pa of 232° it is for all practical purposes in the same direction as the brightest star in the Engagement Ring marked 64. Using Starry Nights Pro software I measured the PA of that star from Polaris as 229° – so Polaris B is just a tad  west of this line.

Not rocket science, but not easy – it pays to sneak up on this one

Knowing that Polaris B is magnitude 9.1, it helps to first find the other numbered stars on this chart. The numbers follow the standard convention for showing magnitudes on a chart in that the decimal point is left out – so the star marked “90” is of magnitude 9.0. Since Polaris B is impacted by the glare of Magnitude 2 Polaris, I used the 9.8 magnitude star as my rough guide to know what to expect to see.

The next question was, however, just how close should I expect Polaris B to be – and for this I took two approaches. First, I did a warm-up exercise with a Televue 85mm. I started at 85X with a 7mm Nagler. My eyes weren’t fully dark adapted and the night was far from perfect, so it took a few moments for Polaris B to pop into view even at that power – but it soon was shining steady and obvious right where it is supposed to be and you wonder why it wasn’t always so obvious.  I then dropped the power systematically, staying on each step until I had a solid, positive identification.  I went to 66X, 54X, 46X, and finally 30X with a 20mm TV Plossl.  That was my lowest solid, consistent view for that session.  I could see it from time to time with a 25mm Sirius Plossl (24X), but I could not see it with a 32mm Antares Plossl – a better 30 or 32mm Plossl should have produced it, though – at least intermittently.

Actually, before I did this with Polaris, I shifted to Mizar and got a clean split right down to 19X using the 32mm Plossl.

The Mizar connection

Why Mizar? Well, it’s nearby, so the sky conditions are pretty much the same.  The two stars, Mizar A and B are much more closely matched in brightness at magnitude 2.2 and 3.9. And finally, the split is similar to that of Polaris at 14.3 seconds vs 18.2 seconds.  While this was a piece of cake for the scope, it’s a good challenge star for the 20X80 binoculars. They do split it cleanly, but it gives me a real good idea of how close I expect Polaris B to be to Polaris A when seen in those same binoculars.

The PA of Mizar's companion is indicated by the short arrow - I think of it as always in the general direction of the 7.6 magnitude star that forms a triangle with Mizar and Alcor. Click chart for a larger version. Prepared from Starry Nights Pro screen shot.

So I split Mizar first with the 20X80 binoculars and once comfortable with that split, moved on to Polaris without changing the focus.

The numbers are precise, but the measurements aren’t

We can be such fools for numbers – see the book “Proofiness.”  But don’t let the numbers associated with binoculars fool you.  They sound precise, but they aren’t.

But first, should you even expect to be able to split Polaris with binoculars? In this case you need to forget about  the usual answer to that question which starts with checking the Dawes limit. The Dawes limit for an 80mm objective is 1.4″   ( Dawes limit = 4.56 arc seconds/Objective diameter in inches.) Ha! Good luck. As star splitters know this is seldom achieved and of course there are  many other variables – local conditions, observer, and the difference in magnitude in the two stars, for example. These all have a significant impact on the true limit of what you can split leaving you with a rough, but useful guide.  However, when you introduce binoculars into the equation all bets are off – the Dawes limit moves from being a reasonable guide to being virtually meaningless.

I like the formula the Sky and Telescope columnist Gary Seronik uses. Because binoculars are low powered instruments, he has a rule of thumb that says the practical splitting limit for a binocular is 300 divided by the power.  By that rule the 20X80 binoculars should be able to split stars separated by just 15 seconds. The Polaris pair is 18.2 seconds apart and should fit comfortably into that rule. And, of course, the Mizar pair are a little closer together than that – and a fairly easy split, which is why I say all of these numbers are just rough guidelines.

What’s more, the numbers on your astronomy equipment may simply be wrong. In fact, the more I read, the more I am convinced that the numbers most of us take on trust and use as if they were absolutes are really approximations. This is certainly the case with binoculars, as Ed Zarenski has frequently reported on Cloudy  Nights over the years.  And Seronik, in the December 2011 Sky and Telescope, pointed this out with one simple test anyone can perform. Point a flashlight into the eyepiece end of a binocular and measure the diameter of the projected circle of light – that’s your effective objective.

Rough and ready flashlight test of the 20X80 Zhummel binoculars. The bright circle of light in the inset shows the working objective diameter the system yields for my particular pair. So while the lens may be 80mm, the effective objective is something closer to 72mm. Click image for a larger view.

If the effective objective measure is off by that much, then what about magnification? I suspect it is wrong as well, not to mention field of view. In fact, it seems like every time someone put a stock binocular to the test they find that in most cases all the key numbers tend to be on the high side. Doesn’t mean there aren’t accurate ones out there – for me it just means take it all with several grains of salt.

That’s one reason why I am not suggesting we have a contest to see who can split Polaris with the least amount of power – but I do encourage you to give it a try and report your results here in the comments after this post being sure to mention exactly what you were using by make and model.  And if you’re new to this game, don’t get discouraged. A decade ago I was feeling very satisfied to split Polaris at high power with a 6-inch!

As for me, I’m going to keep trying. The “intermittent” split I got last night isn’t good enough. I could only hold it for about 10 seconds at a time. What’s more, I want to try the 25X100 Zhumells again on this, plus the 20X60 Pentax – and  I have some 16X70 Fujinons on the way. These last are, according to the reviews I’ve read, really, really good. Wonder if it will make a difference? Since you’re only using the center of the lens, I suspect the inexpensive Zhumells are pretty good – but the Fujinons may do better because of better contrast – and the individual focus eyepieces should do a better job of finding and holding the best focus.

I’ll see. Meanwhile, I expect to use Polaris as a frequent warm-up exercise for star splitting, helping me to fine tune focus, get used to the correct eye position, and telling me when I am well dark adapted – not to mention having something to say about transparency and seeing on any given night.


Seeing double the natural way – looking up with both eyes and binoculars

The best way to look at the stars is to lie back in the grass on a hill side on a warm summer’s night in a region free of light pollution and look up. The only way to improve on this is to add binoculars. And when it comes to splitting doubles, this is doubly true!

Bring on the doubles! - 25X100 Zhummel binoculars.

Binoculars make a terrific double star instrument because you are doing what comes naturally – you are using both eyes and you are looking up. And there are loads of beautiful doubles that provide absolutely charming splits when viewed properly in binoculars. What’s more, binoculars give you a sense of context. Because they give a correct image and wide field of view, the transition from naked eye is not so abrupt or confusing. It’s a great way to learn your way about the night sky and to keep what you view in context.

I should add that once you get past the smaller binoculars it is neither simple, nor cheap –  it actually gets about as complicated, cumbersome, and expensive as using a telescope. Image stabilized binoculars maintain the size and portability we have come to associate with binoculars while making it easy to get a steady view, but they are expensive. However, most of the time I use larger binoculars and their mounts are  as heavy and awkward as any mount and as expensive. There’s no free lunch here – but for me the binocular astronomy experience is well worth the effort and price.

But I have a confession to make. Until very recently I didn’t consider this the case. I thought binoculars did a poor job with doubles – but I now think this was my special hurdle to leap and now that I’m over it I’m in bin ocular double star nirvana – so I decided to provide some basic guide lines for splitting doubles with binoculars, plus a short list of some especially useful binoculars doubles that range from easy to difficult and will give you a way to test yourself and your binoculars, should you care to.

My knowledge comes the hard way – I acquired it through numerous hours of observing and most of them were relatively futile. If you want to read the whole saga of my personal journey with binocular doubles, go here.  But I really think most people have a far, far easier time of it with these inexpensive and highly portable instruments. So let’s get started.

Short List of Binocular Doubles

First, here’s a list of some excellent spring and summer binocular doubles arranged in order of the easiest to the most difficult. The top of the list can be split by any binocular, the mid section takes a good astronomy binocular, such as a 10X50, and the last few call for big astronomy binoculars in the 20X80 or 25X100 range – which can now be acquired quite cheaply, incidentally, but mounting them is the rub.

  • Mizar and AlcorMany can split these two famous stars in the handle of the big Dipper with the naked eye, but for me it always takes binoculars – any binocular.  RA:  13h 24m   Dec:  +54° 56′ – Mag:   2.2, 4  – Sep:  11.8′ (708.5″)  – PA :   71°
  • Epsilon Lyra – Double Double – No, I don’t mean to actually split each star – I mean the initial split into Epsilon 1 and Epsilon 2 – that’s easy for any binocular and since these are in the same low-power binocular field as Vega, easy to find. I am able to split these with my  6.5X21 Pentax “Papilio” – the “butterfly” binoculars.  RA: 18h 44m   Dec: +39° 40′  Mag.: 5, 5.2 –  Sep. : 210″
  • Nu Draconis – The famous “Dragon’s eyes” are delightful because the split is clean with just about any binocular and the stars nearly identical. RA: 17h 32m Dec: +55°11′  Mag: 4.88, 4.86 Sep: 63.4″ PA: 311°
  • 16 & 17 Draconis – This pair is more widely separated and easier to split than Nu, but I listed it after Nu because it is a bit more difficult to find. RA: 16h 36m Dec: +52°55′  Mag: 5.4, 5.4 Sep: 90″ PA: 196°
  • Albireo – Beta Cygni – I think this has got to be one of the most popular double stars there is, and while it mark’s the Swan’s head, it is easier to find with the naked eye, than with binoculars. The reason is it’s in the heart of the Milky Way and it’s hard to know which is the star you seek because there are so many. RA: 19h 31m Dec: +27°58′ Mag: 3.4, 4.7  Sep: 34.7″ PA: 55°
  • Psi Draconis – I know I have the right star when I see the perfect little kite asterism  in my binoculars with Psi as the brightest member – RA: 17h 41.9m   Dec: +72° 09′  Mag.:   4.6, 5.6  Sep:   30.0″  PA:   16°
  • RegulusAlpha Leonis –  With a separation of nearly three minutes of arc you would think this one would be up with the other easy stars – it’s isn’t because the magnitude difference is so great – great enough for me to call ont he light grasp of an 80mm or 100 mm binocular. RA: 10:08:22.1 / Dec: +11:58:01 – Mag.: 1.35, 8.12  Sep.: 177.6  PA: 207°
  • Mizar – Yep, this is the brighter half of Mizar and Alcor and it does make a lovely split, but it takes more binocular muscle – more like 20X and easier with 25X.  RA:  13h 24m   Dec:  +54° 56′   –  Magnitudes   2.2, 3.9 – Separation  14.3″ – Position Angle    153°

Short check list of guidelines for getting the most from your binoculars

Garrett Optical 28X100 binoculars on Universal Astronomics Millenium Mount with rotating beach chair - to me the perfect chair to sit in while using binoculars since it both leans back and rotates, but hard to find and the most recent version of this chair I found was not that well made.

From my experience I’ve developed some basic guidelines for splitting doubles with binoculars.   Many of them you probably already do. If so, treat this as a reminder.

  1. Wear your glasses if you have astigmatism – otherwise do without.  And if you need glasses, seek binoculars with long eye relief and flexible eye cups that roll back.  You only need to see the center of the field to split a double, but the whole field is useful for finding the double.
  2. Sit down – or better, lie back in a lawn chair – you must be comfortable. Get in a position where you are looking at your target area without strain, then bring the binoculars to your eyes. This is important. Even with a nice Parallelogram mount I frequently see people raising their head and straining their necks to look through binoculars. Take the time to make the mount do the work for you.
  3. Hold the binoculars steady – even 7X50s will benefit from being on a tripod, or parallelogram mount unless, of course, they are the image stabilized types. Most people think they can hold binoculars steady. Wrong! And this is doubly wrong if you’re trying to split close doubles. An ordinary photo tripod can hold small and medium binoculars, but will likely result in a pain in the neck. I can’t use one for anything except objects that are so low the atmosphere becomes a problem. However, I know excellent observers who use such amount for all their  binocular observing. I much prefer the kind of parallelogram mount that puts the binoculars to one side of the tripod or pier so you can observe comfortably while seated in a lounge chair. This isn’t laziness – it’s practical considerations related to seeing well.
  4. Focus carefully – very carefully – with center focus types remember to focus first the left eye with the right closed, then do the diopter adjustment for the right eye while keeping the left eye closed. I know everyone should know this already, but it’s surprising how many people have used binoculars casually for years without being aware of it.  Acceptable focus for land views just isn’t the same as the critical focus needed to split close doubles. Once you have the diopter set, you can leave it alone and just use center focus.
  5. Get the interpupilary distance right!  That is, make sure the binoculars are the same distance apart as your eye. This is another one of those things that might evoke a duh! But the truth is, your brain wants to see a single image and might be working overtime to give you one because the binoculars aren’t adjusted properly for your eye. (This is also true if your binoculars are out of collimation – but evaluating and correcting collimation is a topic beyond the scope of this post.)
  6. Spend time on target – Look for at least one solid minute – don’t expect instant success. Don’t fiddle with the focus forever – give your eyes time to adjust. This is one of the key instructions in Crossan and Tiron’s “Binocular Astronomy.” They write:”the most important thing in observing is to really look – a mere glance at an object or a field is simply not enough. You must keep your eyes at the oculars for a full minute at a time.” I can’t stress this enough. over and over again I see people taking mere glances and thinking they have seen all that can be seen. As Holmes told Watson: “You see, but you do not observe.”
  7. Relax your eyes – let them focus at a distance and get used to it. I wish I could explain this better. I feel it’s important, but I’m not sure exactly how to describe it. If I’m in doubt I take down the binoculars and just try to let my eyes focus on the stars. Then I come back to the binocular view.
  8. And if all this fails to deliver sharp star images, 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.

This last has driven me crazy and continues to puzzle because believe me.  Points one through seven didn’t make a difference for me until I could settle the issue of point 8 and right now I’m not sure how many others have a similar problem, but I think it’s relatively few.

I’ve been to both the eye doctor and my massage therapist and right now the one whose advice makes the most sense relative to this situation is my massage therapist. She noticed me holding my head a bit funny and she knew I had flexibility problems with my shoulder and neck. These apparently don’t come into play when I am leaning over the eyepiece in the diagonal of  a refractor or catadioptic telescope – or for that matter, looking directly into the eyepiece of a reflector. But when I look up to look through binoculars, all bets are off. What feels natural to me simply isn’t the position that yields sharp star images. For years I have blamed this on the quality of the binoculars. Then for a while I blamed it on what I perceived as my astigmatism. But tests show that astigmatism is slight and what I am finding is critical is getting my head into a position that works – even if it feels unnatural to do so.

I discovered this by backing away from the eyepieces as much as two or three inches and moving my head around, tilting it in various angles.

My advice to you? Don’t worry about this unless you’ve tried everything else and are still having problems getting sharp star images.

Meanwhile, check out some of the doubles on the short list. Warm up by trying the easiest first – and get your focus right on them. Most are conveniently grouped with other bright stars and easy to track down – and each is distinctive. Even if you have seen them all in telescopes, the binocular view is different and special. Give it a try and see if you don’t agree.

More binocular astronomy resources:

Binocular  Highlights” by Gary Seronik – this is a great book to begin with. It mentions several double stars, but a lot of other good objects to look for with your binoculars. Also, scroll down his web site for some excellent binocular reviews and related suggestions on mounts.

Review of Binocular Mounts – Go here to learn of  some of the possibilities of commercial binocular mounts. If you’re handy with tools, there are plans here for making a parallelogram mount.

Binocular Astronomy, Crossen and TironAgain, a good guide. I have the first edition – have not seen the newer one advertised here, but I assume it is at least as good.  This is a general guide with lots of solid observing advice and several specific doubles.

Binocular Double Star  Club – Here’s a good list to whet your appetite – and if you’re into “awards,” go for it.

2011 in review

The WordPress.com stats helper monkeys prepared a 2011 annual report for this blog.

Here’s an excerpt:

The concert hall at the Syndey Opera House holds 2,700 people. This blog was viewed about 20,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 7 sold-out performances for that many people to see it.

Click here to see the complete report.

DSC-60 – Visiting Mintaka, an old and comfortable friend

This is a DSC-60 Project observation –  for project details go here.
Splitting Tools for Mintaka: Yields easily to 50mm scope at low power.

Data from Double Star Club list

  ] 20 Delta Orionis 05h 32m.0 -00° 18′ 2.2, 6.3 52.6″ 359

Mintaka (Delta (δ) Orionis)
RA: 5h 32m  Dec: -00° 18′
Magnitudes –   2.2,  6.8
Separation –   52.8″
Postion Angle –   0°
Distance:  915 LY
Spectral Classification –  B4

A couple bonus points to note about those stats – first, the declination – this star is just 18 minute south of the celestial equator. In fact, it’s the brightest star that close to the celestial equator.  Combine that with the PA of 0° – due north – and it’s a good way to help get yourself oriented. Oh – and that separation – 52.8 seconds – that’s just a tad more than the width of Jupiter as it appears in our sky when we’re closest to it, as is the case as I write this. So Jupiter could just fit between the two stars!

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

OK, I really should admit it – I don’t get out to Mintaka – Delta (δ) – often enough.  It’s one of those easy doubles I’ve known forever, but it’s in one of the best parts of the best neighborhood in the best universe – well, the only universe I know, although this multiverse idea is beginning to make some sense to me 😉

So this morning I found myself heading west on Orion’s belt, certainly one of the best known asterisms in the sky. Who can miss three perfectly spaced stars of almost even brightness (1.71, 1.68, and 2.2)  and straddling the celestial equator where they can be seen from almost any location in the world?  And Mintaka, a charming double, is one of those three – the western most. But it’s easy to ignore because the belt itself is embedded in a huge open cluster. what’s more, when you look at the other end of the belt  you get  the famous, but nearly invisible, Horsehead Nebula, not to mention the Flame Nebula and the delectable quadrupal star, Sigma Orionis.

But Mintaka is #20 on the Double Star Club list and I just had to see how it looked in a 60mm scope – well, at least my  8-inch SCT masked to 60mm. And it didn’t disappoint. This is not even close to being a challenge, even with a 60mm, but it has it’s own charm. While there’s quite a gap in magnitude between the two, the large angular separation makes this a good object to try to capture with binoculars. In physical terms given the angular separation and distance from us the faint companion orbits the primary at about a quarter of a light year.

What the 8-inch shows is a silver star with a smaller blue star tagging long. Stopped down to 60mm with the off-axis mask, the blue star turns to a steely grey, while the primary remains silvery.  Haas  saw the secondary as “very bluish white” and the primary  as “yellow white” and quotes Smyth and Webb as seeing the companion as “violet.”

Whatever color you see, there’s a lot more to this star that you don’t see.  Jim Kaler writes on his web site that the primary is “ALSO double, and consists of a hot (30,000 Kelvin) class B, slightly evolved, giant star and a somewhat hotter class O star, each radiating near 90,000 times the solar luminosity (after correction for a bit of interstellar dust absorption), each having masses somewhat over 20 times the solar mass. This pair is too close to be separated directly.” In addition, he notes the two stars orbit each other about every six days causing a slight dip of about .2 magnitudes.

Mintaka is another example of how Bayer made things up as he went when it comes to Greek letter designations. Usually the stars in a constellation follow the Greek alphabet starting wiht “alpha” being the brightest. But Mintake is Delta Orionis, yet Mintaka is the seventh brightest stars in Orion. Again, Kaler comes to the rescue here, saying Mintaka “received the Delta designation from Bayer, who lettered the belt stars in order from west to east before dropping down to Orion’s lower half to continue the process.”

Oh – and those two closely matched super stars we know as Mintaka. They’re heading for a short life and fiery doom.  Kaler notes that given their size “their only fate is to explode violently as supernovae.”  Hmmm… and a twin supernovae at that – wouldn’t that be something? What does happen when one star goes supernovae right next to another?

DSC-60: Tackling Meissa with a 60mm SCT!

This is a DSC-60 Project observation –  for project details go here.

from Double Star Club list

[  ] 22 Lamda Orionis 05h 35m.1 +09° 56′ 3.6, 5.5 4.4″ 43°

from John’s post:

Meissa (Lambda [λ] Orionis)
RA: 5h 35.1m  Dec: +09° 56′
Magnitudes –  A: 3.5     B: 5.5     C: 10.7     D: 9.6
Separation –   AB: 4.9″      AC: 28.7″      AD: 78.0″
Postion Angle –   AB: 50°      AC: 185°       AD: 272°
Distance:  1056 LY
Spectral Classification –  A: O8  B: BO.5

So you didn’t know they made a 60mm Schmidt Cassegrain? Niether did I.  But if you have one of the ubiquitous 8-inch SCTs – hmmm, come to think of it, I have three –  you can make an off-axis mask for it and turn it instantly into a color-perfect, 60mm scope. The cost can be close to nothing, the time about half an hour, and, of course, you do no permanent injury to the scope – the mask is something you put on and take off like a lens cap. It just cuts the scope down to 60mm.  I’ll do a separate post on why and how, but the object here is to see how this performs on Meissa a really wonderful star in Orion’s head.

I just got out at 5 am this morning as astronomical twilight began and quickly swung my “parked” SCT  (it stays set-up in a little observatory) to Meissa. What a sight this is. I didn’t even try to split it at first. I just enjoyed the wide field view. And I did this without the mask on the SCT so I was picking up most of that wonderful pattern of stars that make’s up Orion’s head and is part of an obscure open cluster. (See John’s post for details and charts. )

I was using a 24mm Panoptic which yields 83X and roughly a  49-minute field of view.  I wanted more, but serious twilight was closing in and a wider field eyepiece was 100 feet away in the house, so I stuck with the 24mm Pan, absorbed the beauty of the scene, then popped in a 16mm Nagler. Yep. I could see some signs of a split, but the stars were pretty fiery. So I quickly put on the off-axis aperture mask. (The off-axis part is to avoid the central obstruction.)

Voila! I now had 60mm of clear, unobstructed, color-free aperture. And what a difference. Meissa and her brightest companion  – yes, we’re only going after the brightest companion because that’s what the DSC list calls for – and that’s what is easily in reach of 60mm of aperture.  (I stress “easily” because John is always pulling rabbits out of the hat with his 60mm scopes – secondary,  tertiary and whatever you call the fourth star in a multiple just tumble out of his scopes like clowns out of a tiny car in the circus.  Not me. I stick with the easy stuff, by and large. I don’t have John’s eyes,really dark skies, endless patience and observing skills.)

Anyway – these are the sights I love. I just wanted to sit there an absorb it.  A large, white dot tinged with blue, and next to it a fainter, smaller, violet dot. Simply lovely. I mean these were the kind of perfect, round, well-behaved 60mm stars that we thrive on. Such order has a special ascethic of its own. Wonder if I can split it witht he 24mm? Out came the 16mm (125X) and back in went the 24 Pan – and yes, sure enough,there they were. Absolutely exquisite in their delicacy.

And at higher power? Well with an 11mm Nagler (182X) we had a big old honking split.  Yes, skies were steady! And yes, this is too darned much power for a 60mm if you follow the rules, as I generally do, and limit yourself to 60X per inch (2.5X per millimeter)  then 144X should be tops. But the heck with the rules, what about the 9mm Nagler – 222X?  Yes! We certainly have lost light – and eye position becomes absolutely critical, but we still have a perfect pair of stars.

That eye position business is interesting. John and I both became acutely aware of it when we first experimented with masking. The reason for it is simple. The higher the power, the smaller the exit pupil – the cone of light exiting the scope – and so of your eye isn’t in perfect position you don’t see anything.  There’s a wonderful eyepiece calcualtor on the Televue web site which I use when I want data like this and going there I learned that the 16mm Nagler gave me an exit pupil of about half a millimeter with the scope masked  which is right at the limit of what any sensible person recommends. (Hey, that’s 125X and pushing real near to the 60X per inch limit. ) Televue recommends no more than 2.5X per mm which would put the top at 150X and the 13mm Nagler – next in my case – delivers 154X and that, for Televue, is too much. And keep in mind, these folks are in the business of selling us eyepieces – so i put a lot of stock in their recommendations wwhen they start telling me NOT to use certain eyepieces they make.

But . .. who can resist trying? So the 11mm delivered an exit pupil of .33mm and the 9mm of .27mm – ridiculously small cone’s of light. No wonder eye position was absolutely critical.  But this is of more than academic interest. I learned something from it this morning. Eye position is pretty darned critical when you are using full aperture, too!

Now it’s interesting, because you don’t hit the wall – half a millimeter exit pupil – until you put in a 5mm eyepiece into your  8-inch scope – I’m talking unmasked now. WIth 200mm of aperture the numbers change. Using the 2.5X per mm rule that Televue applies you should be able to use 500X. But Televue has another rule that cuts in before then – they recommend 350X as the maximum “regardless of aperture.”  Of course they’ll sell you eyepieces that will take you higher – at least on the typical 8-inch SCT –  but they won’t recommend you use them to deliver such power.

But here’s what I found as I went back to viewing Meissa unmasked: I could see perfect stars  in the 8-inch SCT this morning – conditions were very good – but only if I was very careful to get my eye centered perfectly over the eyepiece. I’m sure someone will tell me that’s because I need to be on the axis of the light cone, or something like that – and this is hardly an entirely new revelation. But quite honestly, before fooling around with masking I was more likely to assume that  when stars  misbehaved it was because:

a – I didn’t have the focus correct

b – seeing was too poor to deliver a sharp image

To these two obvious thing I now have to add eye position, which with my Naglers, at least , is critical. I could really get quite an attarctive  split this morning with quiet , well-behaved stars, at several different powers and full aperture IF I was very careful about eye position.  Not all that easy to do.  I always observe sitting down, of course, but to position your eye correctly you need to really be just at the right height above the eyepiece and  in this case I used a hand to form a brige between the eyepiece  and my face to help steady it. (OK – I’m 70 -maybe younger folks would find this easier.)

If I don’t do this, the view unmasked is pretty if you like dancing, flaming stars.  In between the flaring you do see the split – and the additional aperture does show you the fainter companions John describes – and with the wide field provided by the 24 Pan and bright stars provided by eight inches of light grasp, Meissa really is beautiful. But I am also sure that if I didn’t have such great seeing conditions I would not have seen it that way – the 60mm would have provided an improvement for seeing Meissa A and B as clean, steady, dots. (One  other possibility – the scope I was using is a Meade LT-8 ACF – the Advanced Coma Free variety.  Perhaps that contributed to the view – I just don’t know. It would have been fun to have it go head to head against one of my older SCTs without the advanced design.)

It’s a trap! No it’s THE Trap – the truly awesome Trapezium done DSC-60 style

Hubble photo of Orion Nebulae modifed to put emphasis on the Trapezium. Click on image for larger version.(Flipped left to right as in telescope using a diagonal.)

This is a DSC-60 Project observation for project details go here.
Double Star Club list:
Theta 1 Orionis 05h 35m.3 -05° 23′ 6.7, 7.9, 5.1, 6.7 8.8″,13″, 21.5″ 31° , 132°, 96°

Click for larger image.

Theta 1 Orionis (θ 1 ) – Trapezium 
RA: 05h 35.3m Dec: -05° 23′
Mag: 6.7, 8.0, 5.1, 6.7    Sep & PA: See graphic
Distance: 1350 ly
Spectral type: B1,B0,O6,B0.5

Magnitudes differ somewhat by source – these are from James Kaler and listed A-D, as are the spectral classes. A&B are eclipsing variables.

In my book there is simply no prettier, no more awe inspiring, no more intellectually stimulating sight in the heavens than the Orion Nebulae with the Trapezium at its heart. This four-star trapezoid is easily in reach of any small telescope and positioned near enough to the celestial equator so that it can be observed from just about any where in the world.

When I say this post is “done DSC-60 style”  what I mean is this post  will focus on the four stars in the Double Star Club list  and how they look through a 60mm scope. But these stars are easily reached by even a 50mm refractor.  In fact some say they can be seen with 10X50 binoculars held real steady. I can’t see them that way. My eyes need a 50mm objective and at least 20X to see three of the four stars.  And the sight only gets more interesting – because the surrounding nebula is enhanced – if you use a larger scope and there are two more stars in the Trapezium worth pursuing with larger instruments – and actually more still that are probably out of the reach of amateur observers.

But one of the first lessons the Trapezium offers us is the difference between the human eye and the camera. Look at just about any of the many gorgeous pictures of the Orion Nebula and you will not see the Trapezium no matter how large the telescope used.  You rarely see it in a photograph that even approximates the visual view through a telescope. It certainly doesn’t come through well in the Hubble photo that leads this post, though the nebula is spectacular. But at the telescope your eye will capture the glory of the nebula and the four diamond studs that are the Trapezium.

I’ve been looking at this off and on for more than a half century and it never grows dull, but the view through a 60mm refractor takes me back to my youth and sparks the love affair anew. Here are the pearls you seek – elegantly represented in an out-of-this-world setting. The “C” star glows brightest. I know, we’re used to the brightest star of a multiple star being designated “A,” but in the case of the Trapezium they broke this rule and lettered the brightest four stars in order of RA. The dimmer, more difficult E and F stars do not follow this pattern, however, but they’re out of reach of the 60mm scope so I won’t pursue them here.

Simulation of the low power telescope view of the Trapezium - with the Orion Nebula removed for clarity, but, of course, you will see it with binoculars or telescope. This small image is typical of what the naked eye reveals. Click on it to get a larger version showing the telescope view at low power.

With the naked eye or low power binoculars you see essentially two stars here – the Trapezium looking like one star identified as Theta 1 (θ 1 ) Orionis and what looks like it’s twin, Theta 2 (θ 2 ) Orionis.  Theta 2 is the brightest star in what I call Orion’s Mini-belt. These three stars will probably be the first to catch your eye in a scope and they point to the Trapezium which, of course, unfolds more and more as you increase power. There is about 134 seconds of separation between Theta 1 and Theta 2 – the stars of the Trapezium themselves span about 14-seconds of arc.

I had to play around with the preferences in Starry Night Pro making the stars into tiny specks and get rid of the nebula entirely  in order to simulate the view through my 60mm Unitron refractor at about 36X using a 25mm Ramsden eyepiece – yes, that’s one of the old eyepieces supplied with the scope c. 1970! Of course in the scope I see both the nebula and the Trapesium, so the simulation just can’t do the view justice. What a;ways missing in books and even on the computer screen is the brightness dimension – it gets represented – simulated – by the size of a dot indicating a star, but brightness isn’t size – its – well – brightness! And I think that’s why the live observing experience remains unique and important.

To me there is something magical in such a low power view where the stars are mere pinpoints. I liked this view also because it revealed the nebula for what it is – a burst blister in the surrounding darkness caused by the  huge star-forming region known as the Orion Molecular Cloud. That cloud is far, far larger than what I could see in the telescope field, covering roughly half the constellation of Orion.

I switched to an 18mm Kellner –  I was going completely “retro” on this evening, using the Unitron with its original eyepieces and original Unihex eyepiece holder which includes a less than pristine diagonal.  It just felt right to do this. At this power (50X) the brightness differences of the stars is more apparent and the C star really looks blue to me while across from it the B star still is just a pinprick. (While some have reported color in these stars I see them as white or blue, with duller shades simply a result of the star being fainter.)

Moving up to a 12.5 Kellner (72X) and a 9mm Symetrical (100X) the picture got bigger, but no brighter. Aesthetically I preferred the view at 50X. It had an elegance enhanced by the delicacy of the relatively  dim, B star.

But there are so many things to take in here that you need to just sit and stare and tell yourself what all of this represents. For many years, when confronted with this view, I dreamed of flying in a rocket ship to the Orion nebula – it’s a mere 1,350 light years away – and I imagined looking out the window and seeing these huge, glowing clouds pass by as you do in an airliner.  But the truth is the view would be more like what you see in the simuation above. There would be no clouds! this where the magician of reality  uses great distance to literally pull the wool over our eyes.

My bubble in this respect was broken by Terrence Dickerson in his book “Nightwatch” in which he wrote:

. . . a hypothetical spaceship rocketing through the nebula would encounter only slightly more particles than those recorded in interstellar space. The average density of the nebula is one-millionth the density of a good laboratory vacuum.

Of course it gets much denser near where new stars are forming, since they are pulling material together.

Does that diminish the viewing experience in any way? Heck no! It is a testimony to how distant 1,350 lights years really is. The numbers simply numb us – but try to imagine particles so far apart that there are far fewer of them than in a vacuum on Earth, then imagine us actually seeing them as clouds because we are so far away!

Of course,  the Trapezium at the heart of the nebula is exactly what it appears to be – four hot, young stars that have burned through the dust around them and popped a blister on the huge Orion Molecular Cloud, giving us a look at what is behind that cosmic screen.

And behind the scenes . . .

And then there is the incredible number of stars that are hidden by dust and need to be dug out with infrared observing tools and when they are what we find is the Trap is the tip of the iceberg – an iceberg that holds what is probably the youngest and defintely the most star-packed open cluster we know. The density of this star city is believed to be  6,000 stars per cubic light year – think of what that must be like in comparison to our own region where the nearest star is more than four light years away.  The age is believed to be less than a million years and the Trapezium itself is unstable and will probably vanish in a huge explosion of the C star in the next few million years – so get a look now while you can!

This is all part of what makes the  Trap and surrounding nebula a sight where the sheer majesty overwhelms you. I strongly urge you to click on the following picture to study the larger version. The picture is a composite of what is seen with the Hubble Space Telescope in Visible light and what is seen by the Spitzer Space telescope in infrared light.  As NASA explains it:

Orange-yellow dots revealed by Spitzer are actually infant stars deeply embedded in a cocoon of dust and gas. Hubble showed less embedded stars as specks of green, and foreground stars as blue spots.” All but washed out in the long exposure are the four stars of the Trapezium in the bright area below and to the right of center.

Click image for a larger version of this composite shot in visible light and infra red.

Go here for complete picture and NASA explanation.

Jim Kaler points out more fascinating facts within the Trap itself:

By far the leader of the pack is Theta-1 C, a great 40-solar-mass star with a temperature of 40,000 Kelvin (making it the hottest “naked eye” star, though the 4 are inseparable without optical aid), a huge luminosity 210,000 times that of the Sun (85 percent of the Trapezium’s total), and a 1000 kilometer/second wind with 100,000 times the flow rate of the solar wind. The power of the star is such that it is evaporating dusty disks around nearby new stars that in other settings might form planets.

The other members of the Trapezium pale only in comparison with “C,” all containing over 10 solar masses. A main interest lies in their multiplicity. Theta-1 A is an eclipsing double also known as V 1016 Ori. Every 65 days, the star dips by a magnitude as a star still in the process of formation just one Astronomical Unit away passes in front of the bright component, the whole thing watched by another companion 100 AU off.

Theta-1 D seems to have a companion as well. The champion in this contest, however, is Theta-1 B, which has a companion 60 AU away called “B1.” “B” itself is another eclipser (known also as BM Ori) that drops by nearly a magnitude every 6.5 days, the companion probably much like the Sun. Since “B1” is also double, Theta-1 B is quadruple. Adding them all up (and including fainter Theta-1 E, which lies close by), the Trapezium is a complex multiple of 11 stars!

. . .  Most multiple stars are hierarchical, a distant star going around a close double (like Theta-1 B), or two close doubles going around each other (like Mizar or Epsilon Lyrae), which gives great stability. The Trapezium, on the other hand, is gravitationally unstable, the stars all too close together. As a result, one after the other will be ejected from the group. After only a few million years, the leader of them all, Theta-1 C, will inevitably explode as a great supernova, the others probably doing so as well, all lighting the dusty gases of interstellar space, all providing shock waves that will promote new star formation within the local molecular clouds.

And this is what those little dots of light in your 60mm glass are all about! Awesome. But there’s more.

As I said, the Dickerson statement about the nebula being a vacuum still leaves me a bit confused. It is obviously denser near new stars, else the stars couldn’t form. The question is, how dense does it get and how close to those stars do you have to be  to experience clouds?  More to the point, how dense is matter in the area we actually see in our scopes as nebula? I’m just not sure from what I’ve read. But it is something to think about and while thinking about it, why not sit back and enjoy the Trapezium, the nebula, and starbirth in this wonderful animation.

About this animation

From the Hubble Web site:

This animation reveals the topography and beauty of the Orion Nebula like never before. Based on data obtained by the Hubble Space Telescope, all of the gas clouds, stars and proplyds are positioned as accurately as possible. The animation ends with a close-up examination of the proplyd HST-10, where astronomers see dust grains clumping in the early formation of rocky planets, but whose gaseous envelope is also being burned away by the Trapezium stars in the nebula’s center.

Credit: Greg Bacon (STScI), model based on data by C.R. O’Dell (Vanderbilt University), and The American Museum of Natural History/Rose Center for Earth and Space