Best way to attach CCD to 2" focuser ???

[Skipper Billy]

I am having real problems attaching my CCD/filter wheel assembly to my focuser.

The compression ring of the focuser is sitting half on and half off the lip at the aft end of the safety undercut on the T2/M48 adapter. See attached images. I have tried moving the assembly out a little but the undercut is deep enough to alter the orthagonality depending on which of the 3 focuser screws are tightened first.

Any suggestions for a more positive and accurate way of attaching the camera/filter assembly to the focuser??

 

[johnrt]

Could you pack out the undercut to make it less deep with maybe some PTFE tape?

[Skipper Billy]

Maybe - but I was hoping there might be a more positive system that I don't know about??

I might try filling the undercut in with chemical metal then spinning it true on the lathe as a temporary measure.

[Freddie]

I had the same problem once and gave up and replaced the adaptor with one without a lip. I couldn't find a solution that was solid enough not to introduce droop issues.

[Skipper Billy]

OK - where can I get an M48 - T2 adapter without the undercut?? They all seem to have it ???

[Hicks]

Can you not get an adapter that screws into the focuser instead of using the compression ring?

When I bought my moonlite, although it came with a 1.25" and 2" compression ring adapters, I bought a 68mm to SCT thread adapter instead. That screws directly into the drawtube and then the filter wheel screws into that (my filter wheel came with both a T-Thread plate and SCT that I could switch between though).

Moonlite do a range of adapters and I'd expect the results would be more stable than the compression ring? That is assuming the model you have had a threaded drawtube?

The one I bought was "2 1/2 inch 68mm thread to SCT-thread Adapter (Model 68mmto-SCT-thread-Adapter)" which is listed on the CSL2.5"  page on focuser.com can't seem to get a direct link

[Skipper Billy]

Thanks 'Hicks' - I am pretty sure that my focuser doesnt have a threaded drawtube - I will check as that would be a great solution. 

It seems daft to me to make something as well engineered as the Moonlite focuser then rely on a compression ring to hold the camera/filter wheel in the correct plane.

[r3i]

15 hours ago, Skipper Billy said:

Thanks 'Hicks' - I am pretty sure that my focuser doesnt have a threaded drawtube - I will check as that would be a great solution. 

It seems daft to me to make something as well engineered as the Moonlite focuser then rely on a compression ring to hold the camera/filter wheel in the correct plane.

A fully threaded solution is the way to go.

I think the threaded drawtube is a purchasing option on the larger 2.5" Moonlite focusers.  I looked into getting a Moonlite with the threaded option and a focus motor for my 8"RC a while ago, however the total cost was a bit pricey for me.  In the end I went for an R&P focuser from Teleskop Express in Germany that provides a 63mm thread which, together with an M63 to M48 adapter and an M48 to T-thread adapter, allowed me to get everything screwed together (I made a DIY solution for the focus motor).