Arie's Dobsonian Telescopes

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 The Ingredients
 Secondary cage and trusses
 Mirror box and Mirror cell
 Side wheels and Rocker box
 Argo Navis
 ServoCAT


 The Telescopes
 12 inch
 20 inch
 16 inch
 8 inch


 Binoscope
 Mirror cells
 Tunable top
 Miscollimation to merge images
 Optics and performance
 The WOW factor


 Other enabling companies


 Links

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Binoscope


The noted astronomy writer and columnist Phil Harrington inevitably ends his columns with "And remember that two eyes are better than one". How is that? A lot has been written about the virtues of looking at the night sky with two eyes. It is not diffcult to convince people that looking through a binocular at the moon, planets or bright deep sky objects is a pleasant experience. But even giant binoculars cannot be a match for two, large-mirrored telescopes when it comes to hunting fainter deepsky objects. That is, a combination of such two telescopes, or binoscope.

But why make a tedious and complex combination of two telescopes when you also can use a premium binoviewer on one large mono-telescope? And indeed, a lot has been written about the pros and cons of binoviewers versus binoscopes, with one of the main drawbacks of a binoscope being the complexity to build one. But while that is certainly true, this was exactly what I wanted to do: build a more complex optical system than a mono-Dobson telescope. So I can put all these discussions aside and concentrate on what I did and why I did it.

Of course one can build a giant binoscope in the range of 2 x 22 inch such as the one from Bruce Sayre or a 2 x 16 inch from David Moorhouse, but, as often, practical reasons stand between such a dream and reality. So I considered those binoscopes as a source of inspiration, not examples to follow. For instance, one of the restrictions I put on the binoscope was that I wanted less heavy optics than the described 20 inch mirror. And another restriction was that I wanted to avoid ladders and that is inevitable, even with a 2 x 16 inch binoscope. That is, unless you use pretty fast mirrors. And that didn't sound as advisible for a binoscope either, given the complexity of co-collimation and image merging. So f/5.0 came out as about the optimum for me, with no need for a coma corrector and higher tolerances for collimation etc. Furthermore: no ladder. Adding up all these considerations resulted in a 2 x 13 inch f/5.0 mirror system.

So what does 2 x 13 inch compare to? Lot's of confusion there. The most knowledgable discussions on the web point to about 1.4 times the aperture, so the 2 x 13 inch would compare to about 18 inch. That's good enough for me. A very good article on that subject can be found on the website of Bruce Sayre. A direct link to that article on his website is this. The why of this 1.4 factor, how the brain behaves upon receiving signals through two eyes, phenomenon such as neural summation etc are discussed there.

To make a story short, two almost identical 13 inch f/5.0 mirrors were made by Mike Lockwood. Around these mirrors I built the binoscope below. Was it difficult to make it? Certainly more difficult than any mono-telescope I built, but then again, very doable. In the next sections I'll describe what was different from building mono-telescopes and how I resolved problems I encountered.

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