Hi, I’d like to add an Optec NextGEN Ultra WideField 0.7XL to my refractor. The NextGen recommended distance from focal plane to connecting thread is 63.4 mm and a difference of 1 mm can already degrade the image quality. To connect the Nextgen to T2 (the output of my Sbig STF-8300), Optec has mount plate that is 17,00 mm , but I have also an OAG-8300 and a FW8-8300 and total back focus is 58,2mm. So, if I understand well the Sbig focus table, there is no way to use the OAG because 58,2+17=75,2 mm Without OAG I have 35,4+17=52,4 mm In this case I could use a 11mm T2 spacer to arrive exactly at 63,4 mm Could someone confirm that my argument is correct? I really would like to use the OAG and I wonder if there is a solution to use it. Thanks a lot Giulio NextGEN Ultra WideField 0.7XL http://www.optecinc.com/astronomy/catalog/nextgen/17409.htm Optec NextGEN Mounting Plate Finder http://www.optecinc.com/astronomy/catalog/nextgen/nextgen_mounts.htm Sbig backfocus table https://www.sbig.com/support/product-documentation/backfocus-table/
To use the OAG you would have to pick a different reducer since the distance from the reducer 63.4 mm Optec does have the spacer for the system without the OAG. SBIG STF-8300 with CFW5/8-8300 and T-thread adapter with 3mm thick filters.0.62 17392-0.62
Thank you Tim, but It seems like there is not so much choice to get a different reducer for refractor telescope on the market. At least I don't know it. The only choice seems to use a guide scope. Regards Giulio
