AstroDoc1

Definitely 5.4mm is the starting gap then adjust from there to improve the star shapes in the corners. I use a backfocus of 56mm because I add 1 mm for the 1/3 thickness of the filters. Let me know how you make out. Brian

I just received this scope and flattener. is 3.45mm definitely the correct flattener gap space for a 55mm back focus with the ZWOasi2600mm camera? I thought I read somewhere it should be 5.4mm. I need confirmation. thanks, brian