Can you buy 1.25" Crayford focussers?

[Omaroo]

Hi all :)

I'm just curious (because I haven't been able to find any yet) whether or not anyone knows if you can actually buy 1.25" crayford focuser assemblies at all? I'd like a pair of them for the bino scope, so that the diagonals don't hit each other as they are likely to with 2" diagonals inserted as they are swung around to meet interocular requirements. I'm trying to stay with the narrower option if I can....as it's lighter too. Two focusser assemblies with diags and EP's add up to quite a bit of top-end weight - which I don't particularly want to have to compensate for down below.

Cheers
Chris

[Satchmo]

Hi Chris

Remember that you still have to get an F5 light cone through the focusser before the 1.25" star diagonal, so the back focus is quite long and a 1.25" draw tube won't cut it, a 2" focusser is mandatory .

The easiest lightest solution is the JMI 2" `reverse' Crayford with 1.25" adapter( as seen on the last 3 Ozzie/Kiwi binoscopes). A Chinese Crayford would also do, but there is a big weight penalty there ;)

Mark

[Omaroo]

Aha! OK Mark - thanks. I could have sworn that Paul's 12" unit you brought along to Lostock had 1.25" focusers. I'll look into the JMI units. Thanks!

I think that I'll need to start looking at getting some dimensional data off you pretty soon so that I can start putting together some plans.

Cheers
Chris

[larry brockman]

I have a 200mm Reverse Binocular Telescope under construction. My plan incorporates 2 X standard OTA f8. The inner pupillary fine adjustment is via the standard 2" rack & pinions supplied on OTA. 1.25 diagonals are adapted to the focusers to turn them 90 degrees. I then plan on using a Helical Focuser that has a 1.25 nose piece directly into the diagonal. The other side of the Helical suits a 1.25 eye piece. I will set the OTA and rack & pinions to meet near focus when mounted in the main frame and the Helical’s to do the fine focus. I have the parts on order and will do a test run before I finalize the design. I have gone this way to avoid rotating the OTA to adjust the inner pupillary setting. My theory , the less moving parts the better.
I did look at 2" focusers , helicals and eyepieces etc. all were too bulky to meet minimum pupillary settings.
I should have the Helical’s next week and will do a test run with one of the OTA’s and know better how they might work.

Best regards Larry Brockman

[Omaroo]

Excellent Larry! :)

I'd be keen to keep up with your progress on this project. I'm now a firm believer that bino's are going to become a bit more prevalent as time goes on. They are just so damn great to view though.

Cheers
Chris

[larry brockman]

Thanks for your interest , I will keep in touch as things progress.

Regards Larry Brockman

P.S. Gee I would love to see the shed you keep all your gear in.