Binoscope VS Binoviewer

Hi.
The idea of a binoscope is very exciting and interesting. However the idea of building one and alligning all the optics for two scopes to get two images to merge is very daunting.

Naturally, just dropping in a binoviewer into a 'normal' scope is much easier.

My question is this: is an 18" dob with an 10 square inch obstruction due to secondary and a binoviewer any different really than a binoscope with two 12.5" primaries and two 5 square inch secondary obstructions?

Aren't the 2 12.5" primaries really just the same (more or less) as one bigger 18" primary. Isn't an 18" easier to build and collimate? Isn't 1 secondary preferable to 2? and isn't the binoviewer paid for by not having to buy 2 spiders (never mind 2 diffraction patterns...but I bet you could align those if you are carefull...still, you might be adding them), 2 secondaries and 2 moonlites? Plus if you want to go back to full aperture monoscope, you have an 18"-er.


Thought of the day.

TomL

Maybe that's why you see a lot of binoviewers but few binoscopes.

Doug

Building a binoscope is much more difficult. You've got to have matched primaries. Then you have to collimate each side of the scope, and then be able to merge the two images.

Optically they are a little different also. If you keep the focal length the same the two telescopes (18" vs 12.5") the 12.5" might be an f/6 with a 75" FL. The 18" would need to be f/4.16, so much more coma and chance for other optical defects. If you keep the focal ratios the same, then you are going to have a smaller field of view, as well as a ladder to deal with.

Hi Tom,

There are lots of posts about this type of issue in earlier threads. You might consider doing a search on "binoscope" to see what pops up.

To me you're argument makes perfect sense, and I think most folks would agree.

It's hard to quantify the effect of a seperate column of light going into each eye, vs. a single column split, and half of the light going into each eye (even if you compensate with more aperature. It is a different effect, but is it worth the extra hassle and cost? Most would say no.

But if you get a chance to see this sometime, you might like it. Unfortunately, I have become hooked. Maybe the voice of reason will rescue you from this path.

David Simons

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