Our observatory has a STXL-6303, FW8G-STXL, and I ordered the standard cover... still waiting for FedEx to deliver. We also have a Takahashi Epsilon 200 astrograph that we would like to use for imaging. I need to order a custom adapter from Precise Parts to connect the filter wheel to the Tak corrector lens. The Tak corrector lens has a metal back focus distance of 59.8mm (see attached schematic) and the guided filter wheel has an optical backfocus with 3mm filters of 59.87... which means I cannot use the guided filter wheel, it would be just beyond focus when including a 1.0mm effective adapter length. This is okay, we already have a dedicated guide scope on the Tak. I planned on also using the 6303 with Nikon lenses, which is why I ordered the standard cover, but I got to thinking and the standard, non-guiding, filter wheel has an optical backfocus with 3mm filters of 42.77mm. This would give me 17.0mm of effective adapter length and I could hit focus with this setup. My question is: What is the optical backfocus with and without 3mm filters of the FW8G with the standard cover installed?
Look at the table here: http://www.sbig.com/support/product-documentation/backfocus-table/ Camera + standard filter wheel - without 3" accessory ring - no filters is 43.5mm Be sure to check the table.
Excellent. So the only difference between the Guided and Standard filterwheel is the cover? The back is universal? If so, this makes me very happy.
Correct, see - http://www.sbig.com/site/assets/files/1415/stxl_filterwheel_manual_022613.pdf Canon and Nikon Lens Adapters Canon EOS and Nikon lens adapters are compatible with the FW8S-STXL standard filter wheel. They cannot be used with the self-guiding filter wheel because the back focus requirements of the lenses are too short for the self-guiding version. In this case, one can use the self-guiding cover for longer focal length telescopes and add the standard cover for use with camera lenses where external guiding is quite acceptable. Guiding with the standard filter wheel can be accomplished using the remote guide head or separate guider like the ST-I.
