I'm trying to binoview the sun through a 1.25" Herschel wedge, so a barlow / GPC in front of the diagonal would not make sense. Also the binotron 27's body thread was a bit larger than the standard 1.25" filter thread. Who knows what exactly the "binotron-27" thread spec is, and Russ would not tell me lol. Most 1.25" eyepiece filters cannot connect because the male thread is just a bit too small.
I tried out one low tech low budget solution:
A barlow with a detachable lens cell:
https://www.amazon.c...d_source=1&th=1
I was also lucky to find an atypical 1.25 filter that will thread into the binoviewer body. It was maybe just slightly larger than standard. But for some reason it cannot go all in. As you can see in the pic there is still a small gap left between the filter and the body. Anyway, I unscrewed the filter glass and use this as an adapter.
It worked! The sun comes into focus in my refractor and the contrast was so much better than single eye! I can see so much more! But at the same time it was clear that the barlow is operating at a much higher magnification than designed, due to the long light path of the binoviewer.
While it's kinda nice, I am still wondering about the proper solution here. I've heard people say that if the barlow is used with a larger spacing than designed the image will degrade. Not sure whether that is true.
Also the connection is not very secure between the binoviewer body and the filter housing.
Does anyone know a better solution?
Edited by wolfli, 21 June 2024 - 10:26 PM.