Hi, I am planning to order a custom adapter from Precise Parts so that my STF-8300+FW8 (no OAG) will meet the 55mm reference used by two of my telescopes. I am planning to replace the threaded adapter plate with the the "bolted" version of the STF8300/FW adapter on the camera side of the PP order page. The telescope side will just be a generic t-thread. From the backfocus table on the SBIG site, it appears the backfocus for the STF-8300+FW8 without the supplied threaded adapter plate is 34.7mm. This is for Baader 36mm filters (LRGB + Ha, OIII, SII). They came with the camera, as supplied by OPT. The OPT documentation says they are 2mm thick. So, it appears that I need an adapter with an effective length of 20.3mm, as shown: 55mm reference length - 34.7mm from backfocus table = 20.3mm adapter length So, before I go ahead and order this part, can you confirm that my numbers are correct? Thanks, David PS: given the popularity of the 55mm reference, this might be a great optional part for SBIG to carry for this camera. If anything, it would eliminate end-user confusion and cut down on support tickets
Hi David, 34.7mm if the backfocus for STF-8300+FW8 (no OAG) and 2mm thick Baader filters. Keep in mind there are hundreds of combinations so its very hard to carry every adapter. The plate below adds 3.7mm. http://www.sbig.com/products/accessories/cover-t-thread/ Call anytime if you need assistance. Regards Tim
Hi Tim, Thanks for the confirmation. Indeed there are lots of combinations, so I understand why its not a standard option. It would only make sense if the demand warrants it. thanks, David
Hi Tim, I have a similar back focus question and concern. I recently acquired a used ST-2000XM camera with a CFW8a filter wheel installed. I am not clear on exactly what length of spacer I will need to achieve focus with this setup. Can you help me out? Just installing it as described with no space into me focuser tube (Stellarvue SV110 ED) I was not able to achieve focus. Thanks, Les
Les, The back focus of that camera is "0.92 inch http://archive.sbig.com/pdffiles/USBmanRev14.pdf The CFW8a is "1.0 inch I would contact Vic at 530-823-7796 and find out what parts you need. The OTA is discontinued so there is not a published sheet available. You can always reach me by phone or email pics Best regards Tim
