Didge Is there a way to attach an EFW (7 x 36mm) to an M54 camera (eg 2600 Duo) using a method other than screws ?
Yes you can, except that the camera angle vs the EFW angle will be skewed (i.e., will cause third axis balance problem if your mount does not have enough torque). QHY cameras have an adjustable circular slot to make such adjustments; ZWO's camera do not.
If that is acceptabe to you, get a 54mm spacer that is about 8mm thick and threaded all the way (called a "Retaining Ring" at PreciseParts.com). 4mm of the retaining ring threads into the EFW, and the rest is threaded into camera's 54mm female flange.
The retaining ring could introduce extra vignetting, depending on the f-number of your OTA.
You may be able to find "zero thickness" M54-M48 adapters, where the outside male thread is M54, and the inside female thread is M48. But such a spacer will have a hole size of M48 and potentially introduce even more vignetting. Plus possibly weird diffraction pattern from the M48 thread.
If backfocus is not a problem, just use a M54 to M54 adapter (both ends of spacer are male threads). I have bought some (with 3mm optical path) from Cyclops Optics a few years ago. They may be more readily available elsewhere nowadays.
As with retaining rings, the M54-M54 adapter can cause the camera angle to be wrong. The ZWO components are not threaded so that all threads start at the same angles. Now, you can rotate the ZWO "tilt plate" (they call them that, but don't have the proper grub screw to implement tilt) by 60º, so the camera angle can be adjusted so that it is no more than 30º), but still not ideal. It is as if they do not use the products that they "design."
I have personally use direct attachment and swapping carousels instead of swapping EFWs. I.e., buy two EFW, throw the shell of one of them away, so you only have one shell and two carousels. Instead of moving the entire EFW, I just swap the carousels.
Chen
