Quote:
Originally Posted by AdamJL
would be good to let us know what filter wheel? The Sigma has a backspace of 44mm (more like 44.1mm but anyway).
Your camera takes up 6.5mm. That means your adapter and filter wheel need to be 37.5mm. Your "short adapter" is 17.5mm, so you've got 20mm to play with for your filter wheel and any spacers. What filter wheel do you own?
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I think all the ZWO filterwheels are 20mm "thick" so they should all be OK to use, refer...
ZWO 7x36mm...
https://astronomy-imaging-camera.com...zwo-efw-7x36mm
ZWO 5x2" & 7x2"...
https://astronomy-imaging-camera.com...7-x-2%e2%80%b3
ZWO 8x1.25"/31mm...
https://astronomy-imaging-camera.com...nch-or-7x-36mm
ZWO EFW Mini 5x1.25"...
https://astronomy-imaging-camera.com/product/efw-mini
ZWO EFW Manual 5x1.25"...
https://astronomy-imaging-camera.com...on-1-25-manual
All specified in their literature as 20mm "thickness". It's must be, as you've suggested Adam, a non ZWO filter-wheel used or there's a wayward spacer in there or perhaps not as shown in the system diagram below.... ???
Graham,
The system diagram for the ZWO 1600mm Pro here
Shows the ZWO1600mm
directly screwed on to their various models of 20mm thick filter wheels and then screwed to the "EOS Adapter for EFW +1600" adapter to which the lens is mounted. Check that is what you have setup with no extras, except
perhaps for some thin (sub mm) tuning spacers.
Best
JA