March 11, 2017: Astronomy Binoculars

Last week I had my Oberwerk 12×60 binoculars out for the moon’s occultation of Aldebaran.  I hadn’t used them in a while, and I had been sort of unsatisfied with them for a longer while.  Why?  Because they were giving me double images, as well as eyestrain and headaches as a result from not being able to merge the two images.  I just couldn’t really use them very much.

Any pair of binoculars will deliver slightly different – and slightly out-of-sync – images to each eye.  It is your brain’s job to then merge these two images into one.  Your brain is constantly doing this all day long, even without binoculars.  Whenever your eyes look at anything, due to the parallax that comes with looking at something from two different locations.  It is the distance between your eyes that causes an offset in the images, which allows your brain to judge distances to things.

Binoculars are incapable of doing this for anything, say, greater than a mile or so away, because the parallax created by the distance between the two lenses is just too small.  But because you’re still using two eyes to view things through binoculars, the brain still interprets objects viewed through binoculars as being offset, leading to a pseudo-3D effect.  You perceive things, even things like the moon, a quarter of a million miles away, as having distance and shape and standing out from the background.  The same pseudo-3D effect is also at work when you use binoviewers in a telescope on the planets.

When I used my binoculars for the first time in a long while last week, they were delivering two very different views of the moon – offset not just left to right (which is normal in any pair of binoculars, and which the brain can compensate for and still merge, to a degree), but also offset up and down as well.  The brain can’t merge a vertical offset like that.  My binoculars were definitely out of collimation, and were literally a pain to use.  (If you’re wondering how I used them to observe the Aldebaran occultation anyway, it’s simple:  I just closed one eye.)

Uh oh.  My dreaded bugaboo, my Achilles’ heel:  collimation.  As many of the 9 regular readers of this blog know, due to an awful experience with a junky Bird-Jones scope a dozen years ago, I am decidely collimation-phobic.  This is why I have thus far stuck to Maks and ‘fracs – two types of scopes that don’t really need collimation, or if they do, only need it once every few years.  As I wrote last week, I am trying to overcome this fear by moving onto an SCT.  I’ve watched videos, like this one, and this one, describing how to collimate an SCT, and it just doesn’t look too hard.  More to the point, it doesn’t look too hard for me.  In any case, it looks a lot simpler than Newtonian collimation, where, to my mind, there are just too many variables in play.

So instead of just trying to fix the problem, I decided to look for new binoculars.  Truth be told, the 12×60 Oberwerks I own are actually a little too much for me to use well.  The advice I give to beginners in terms of buying binoculars is to stop at 10x50s, because any larger and the binoculars will be too heavy to hold steadily for any length of time, unless your name is Ah-nold.  If the magnification is too high, you won’t be able to hold them still enough to see things – your natural inability to remain stock still will cause vibrations that will overwhelm the view.

oberwerk back
A slightly newer version of my Oberwerk (und underpaid) 12x60s

I decided to take my own advice and look for a pair of 10x50s.  But man, there are a helluva lotta models out there!  To whittle the number down, I “had to” become somewhat expert on binoculars, or at least more knowledgeable, checking out a number of different websites for information and recommendations, and looking at various features, to try to narrow things down from hundreds of models to just a dozen or so.

Now, I wanted to get some good binocs, a quality pair.  Sure, I could buy pretty much any cheapo pair for $50 or even $30 – there are plenty out there – and they would work pretty well for me.  But I want better than cheapo.  Cheapo binoculars, like Celestron’s SkyMaster 15×70 binocs, suffer inordinately from collimation problems – the same collimation problems that were keeping me from using my Oberwerks.  My understanding with those sixty-five dollar Celestrons is that if you buy them, you have to be prepared to return them once, twice, even three times, because such a high proportion of them are out of collimation when you buy them.  And even if they’re not out of collimation when you buy them, you have to carry them around like eggs to keep them from falling out of collimation from a bump or two.

I don’t want cheapo.  I want good.  What differentiates good from cheap?  Consider this an expansion on my entry about Astronomy Binoculars from last year’s buying guide.

First, as a preliminary matter, any binoculars for astronomy should have porro prisms, and not roof prisms.  Unless you’re prepared to spend a whole lotta money on a pair of binoculars with roof prisms – like well over $200 or so, which I’m not prepared to spend on binocs.  Porro prism binoculars have that familiar offset binocular shape, like my Oberwerks, pictured above, as opposed to a straight-through design that roof prism binoculars have.

Second, the prisms used in the binoculars should be made out of BaK-4 glass, not BK-7, which is cheaper quality glass and not as good as BaK-4. Typically, binoculars under about $50-60 or so will have the cheaper BK-7 prisms.  If you want to save money on binoculars, this is one way to go.

Third, you want to make sure that they are not “permafocus” or “self-focusing”, but instead that they do have a focus knob.  Additionally, they should also have an individual diopter adjustment.  This is a separate focus adjustment on at least one of the eyepieces which allows you to focus it separately from the main focus knob in the center.  The diopter lets you adjust for the difference in focus between your two eyes.

Fourth, 10x50s should have at least a six-degree field of view, and obviously, more is better, like 6.5 degrees.  Remember that a seemingly small difference like that is actually larger than it appears because the larger diameter means a much larger area – the formula for area is Pi multiplied by the radius squared.  A 6-degree TFOV shows you a patch of sky that’s 113 square degrees in area; a 6.5 shows you 133; and a 7 shows you 154.  That’s a huge difference.

Fifth, and finally, the binoculars should have fully-multi-coated optics, which is a good indicia of a quality pair.  Never buy any binoculars with ruby-coated lenses, as this is a hallmark of cheapitude.  Binocs with FMC will allow more light transmission than those that aren’t.  However, this particular requirement isn’t quite a dealbreaker; binocs with “only” multicoated optics aren’t awful or anything – they’ll just be a smidge dimmer.

Note that if you’re reading the description of a pair of binocs, and it just doesn’t discuss a particular feature, check some other websites.  Not listing a positive feature more than likely means that it doesn’t have that particular feature.  And if it doesn’t explicitly state that it has what you want, you should walk away.

I looked into regular binocs, you know, the normal kind we’re all familiar with.  But I also researched the image stabilization binoculars, mostly from Canon.  I had tried these out once at an outreach event in Manhattan last May and was fairly amazed.  Fifteen times magnification, and nary a shake in sight.  Impressive; most impressive.  The detail and resolution were even greater than 15x because the image was so rock-steady.

When I went home and looked them up, I was then fairly amazed at the price – those Canon 15×50 IS binocs were about a thousand dollars.  Oof.  And the reviews on them weren’t even so hot – there were numerous complaints that the rubber eyecups degraded and just fell away after only a couple of years.  Like the people who wrote those reviews, for a solid grand, I expect better quality than that.

With all that in mind, which binoculars was I looking at to buy?  Well, I found three different models that I was interested in:

1.  The Bushnell Legacy WP 10×50 binocs, $85.  These are about the least expensive binoculars that meet all the above requirements – BaK-4 porro prisms, fully multi-coated, center focus with diopter adjustment.  I am personally prejudiced against the Bushnell brand name, because they seem to be the most commonly found binoculars at garage sales and thrift shops.  That prejudice is unwarranted; Bushnells get good reviews for quality.  This model not only hits on all cylinders, but it is also waterproof to boot, and has a 6.6 degree TFOV.  Plus, you can get them even cheaper than at that Amazon link by buying them at Jet.com and using the coupon code “triple15” for 15% off your first three orders – bringing the price down to $78.  However, they weigh 2.8 lbs., which is pretty heavy.

2.  The Orion Scenix Wide Angle 10×50 binocs, $93.  These have BaK-4 porro prisms, center focus with diopter adjustment, but are only multi-coated, not FMC.  However, they have a full 7 degrees TFOV, and weigh only 1.8 lbs., which are very light as binoculars go.  Other than that FMC business, these would be a really good buy.

3.  The Nikon Action EX Extreme 10×50 binocs, $153.  These have all five attributes, including a nice 6.5 degree TFOV, but obviously they are almost twice as expensive as the Bushnells, above.  The recommendation in favor of these are that they are very solidly made.  In other words, they can take quite a knocking and still maintain their collimation – and if that’s not a hallmark of quality, then nothing is.  These weigh “only” 2.25 lbs., much lighter than the Bushnells.  Even at the price, this was definitely worth considering, because I think it’s the weight that causes my current binocs to be difficult to use for very long.  My “lightweight” Oberwerks are supposedly 2.6 lbs., which is still kind of heavy.

You probably already know how this story ends.  I didn’t end up buying new binocs.  Instead, I decided, “what the hell, let me give collimating these a shot.”  I mean, if they were “useless” to the point that I couldn’t even really use them anymore, I may as well play around with them – at least to the extent of trying to fix them.  I certainly couldn’t make them any more unusable.

The instructions to collimate them were right there on the Oberwerk website.  And they absolutely couldn’t be easier.  On each half, right underneath the rubber armor, is a single screw.  Even without the instructions, it wouldn’t have been all that hard – turn the screw one way, the image gets worse; turn it the other way, and the image gets better.  Simple.

But the instructions made it even easier than that.  Turn the right screw clockwise, and you will move its image down and to the left.  Turn the left screw clockwise, and you will move its image down and to the right.  Since the image in mine was offset where the right image was both higher and too far to the right, a half turn on the right side, and less than a quarter turn on the left, made the alignment perfect.  The images merged.  Nice!  I’ve got my astronomy binoculars back, baby!

Next time:  Observing in Canyonlands National Park!

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