Various Reviews, Page 11

By Ed Ting

Updated 12/20/11

1) William Optics Binoviewer 


1) William Optics Binoviewer  12/20/11

(1.25" binoviewer, 1.6X multiplier, two 20 mm Plossl eyepieces, heavy duty box/carrying case, $225 - $250 street)

It sounds like a simple proposition.  Split the image into two, put in a pair of your favorite eyepieces, and enjoy the freedom of viewing with two eyes.  But as anyone who's done it will tell you, things aren't quite that simple.  While binoviewing can yield tremendous rewards, there are many complications to getting there.  Consider:

The WO binoviewer package - a lot of nice equipment for ~$250

After reading the above, you may be wondering - why bother at all?  Well...if you've ever looked through a properly set up binoviewing rig, you know why.  The views can be simply stunning.  Remember your wonder and fascination when you first looked at the moon through a telescope?  Get ready to experience that feeling again.  Looking with two eyes seems to relax the brain and body, and you want to linger on the object.  This holds true for planets and (if you can get it to work on your scope) on deep sky objects as well.  Everything seems to take on a 3-D look and it can be hard to tear yourself away from the view.  For a real treat, point your scope at the moon, turn off the drives, and watch the moon drift across the field of view.  You'll feel like you're flying across the surface.

William Optics binoviewer on the Celestron C6.  Note thread-on diagonal.

Much has changed since my last binoview article back in 2000.  Back then, binoviewing was a fringe activity done by wealthy observers.  Today binoviewers are an enthusiastic, vocal bunch, and exert influence on observers and manufacturers alike (recently, TeleVue shaved 1 mm off the diameter of its 13 mm Ethos so that more observers could use them in binoviewers.)  

Roughly speaking, binoviewers fall into two classes: those costing about $1000, and those costing about $200 ("middle class" products such as the original Denkmeier and the Burgess attempt to bridge the gap with models costing about $500.)  In the past, if you owned a $200 binoviewer, it meant one thing - some poor microscope sacrificed its head for an astronomer.  Microscope head-based units were easily recognizable from their 45 degree erect-image prisms and .965" eyepieces (and, sadly, by their often poor performance.)  Today things have changed.  There is no shame in owning a $200 binoviewer.  While they have smaller prisms and reduced clear apertures as a result, within those bounds they perform perfectly well and allow more astronomers to experience the thrill of binoview observing.

No one's talking, but the WO unit appears to be very similar to $200 binoviewers sold by Celestron and Orion.  I selected the WO because of its intriguing 1.6X barlow.  This is much a lower powered multiplier than any other I'd seen.  Most other units are sold with a 2X barlow.  I showed the ad to local club member John P, who is the club's de facto bino view expert (John owns a TeleVue and a Denk II, along with a duffel bag full of binoview accessories.)  He expressed doubt, smiling and shaking his head at the same time.  Lower powered binoview barlows tend to be longer, not shorter (the WO 1.6X barlow is the stubbiest, shortest barlow I've ever seen.)  Still, I figured that even if the barlow didn't work as advertised, the unit was still a bargain.

The William Optics binoviewer arrived in a nice, sturdy cardboard case.  Taking the unit out, I was impressed by its hefty build quality.  The binoviewer comes with a pair of 20 mm "Swan" eyepieces with a claimed 66 degree field of view.  The barlow was perhaps the only disappointment - it's small and seems way too light.

I was fortunate to have a variety of scopes at hand for testing the binoviewer.  I tried the unit in the C90, C5, C6, C8, a Starmaster Oak Classic, and Orion Short Tube 80, a Pronto, a Takahashi FS-60CSV, and 12.5" and 20" Obsessions.  After playing musical chairs with the equipment for months, I found the C5, C6, and the Oak Classic were the bet fit.  On the Starmaster, I had to move the mirror all the way up to find focus.  And when all was said and done, I found myself using the binoviewer on the C6 over 90% of the time.

But enough of all this.  You don't care about any of the above, do you?  What you want to know is this - does a typical $200 binoviewer give you the same experience as the more expensive units?

The answer, I'm afraid, is no.

Having said that, a $200 binoviewer with sensible 20 mm or 25 mm Plossls will knock your socks off while viewing the moon.  At one local skywatch, a club member said the view of the moon through the WO/C5/CG-5 combination was the best he'd ever seen.  You may also get decent views of Jupiter and Saturn, provided you don't push the power too high.  Deep sky is tough.  With the smaller prisms, you lose a lot of light.  I never did get the binoviewer to find focus in the 12.5" Obsession, either with or without the supplied 1.6 X multiplier.  It didn't work in the Oak Classic either.  All of this started me wondering what the purpose of the barlow was.  I'm thinking it's just to boost the power, not to help you find focus.  However, as stated above, boosting the power is the last thing you want in a binoviewer.  In the end, I wound up putting the 1.6X barlow away and haven't used it since.  

You can play games with your own barlows.  I tried slipping my TeleVue 1.8X, 2X, 2.5X, and Meade 3X barlows over the nosepiece to see what would happen.  In the 12.5" Obsession, only the 2X would find focus, and only if I moved the mirror up all the way.  Unfortunately, moving the mirror up meant that I could no longer find focus with my eyepieces.  Since the views through the WO/2X combination weren't anything to write home about, I stopped using it this way and moved the mirror back to its original position.

Even cheap eyepieces like the Celestron 25 mm E-Lux work well.  

One of the most expensive parts of any binoviewer are the internal prisms.  When manufacturers start to cut corners on any binoviewers, the first thing that happens is the prisms start to shrink.  The same holds true for binoculars - cheap binoculars have much smaller prisms inside.  This is hard to evaluate unless you hold the binoculars up to the light to see the exit pupils.  In a nice pair of binoculars, exit pupils are nice and round.  Cheaper binos will have squared off exit pupils.

The result of the shrunken prisms is that the clear apertures of the binoviewers also shrink.  Top quality binoviewers like the Denk II and the TeleVue have massive prisms inside, yielding nice big 26 mm or 27 mm clear apertures.  Cheap binoviewers have a considerably smaller spec - 20.2 mm in the case of these WOs.  Does this matter?  Absolutely.  First, the difference between 20 mm and 27 mm is huge - over half a magnitude.  The nice binoviewers are going to throw out a noticeably brighter image.  Just as importantly, the smaller 20 mm clear aperture is going to limit the kinds of eyepieces you can use - most significantly, the big low-power eyepieces you were planning on using.  Most 32 mm Plossls, for example, have about a 25 mm clear aperture.  Not only will the image be dimmer, you may see vignetting around the edges.  Ever wonder why cheap binoviewers are always sold with a pair of 20 mm eyepieces?  They're not being nice to you, they're hoping you don't go experimenting too much.  I've looked through many pairs of eyepieces with the WO, and have come up with a partial list of what works:

Again, if you have a full-sized binoviewer like the TeleVue, Denk II, or Baader, you can use any eyepieces you want without fear of vignetting.  I don't have the money to buy two 13 mm Ethos eyepieces, but those who have tried them tell me the view is stunning.  

The William Optics binoviewer is excellent value for the money and gives a taste of that binoview glory for a fraction of the cost of the expensive units.  On the other hand, if you are truly dedicated to binoview observing, you really do need one of the nicer units.  The TeleVue and Baader are self-contained "set it and forget it" products - there isn't much to modify.  If you're a tinkerer, you might be happier with a Denkmeier.  Seeing all their combinations of nosepieces, multipliers, and various accessories in various configurations makes my head hurt, but Denk owners are more than happy to experiment.

Binoviewing has become a regular part of my observing now.  I use the binoviewer about 25% of the time.  If you haven't used one before, check one out.  You may find that you just have to get one.

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