The field flattener thats forsale, is it ok for my scope?

[Rustang]

Ive been keeping an eye out for a field flattener for my recently purchased SW 80 ED DS PRO, I'm interested in the current TeleVue FF/reducer that's for sale and wanted to double check it should be ok. It states in the details below it has a 55mm back focus which I need for my DSLR and if its reduces the TV-85 which is 600mm FL to 480 then I guess it will do the same to my 600FL and make it an F6!? I like the fact I wouldn't need to buy an extra adapter for it to go in focus tube like whats needed for the Sky-Watcher .85x Reducer/Flattener!

"TeleVue TRF-2008 0.8x Reducer/Flattener for TV-85, TV-76 and Other 400-600mm Refractors

Model TRF-2008 0.8x Reducer/Flattener converts TV-85 to 480mm f/5.6 and TV-76 to 380mm f/5.0 for flat field, fast photography.

Fully multi-coated 3-element unit with 48mm filter thread inserts directly into 2" focuser, accepts standard T-rings for 35mm cameras.

"This accessory is a must-have for someone planning to use the TV-85 photographically" - review in Sky & Telescope, July 1999.

Also it can be used with any 400-600mm refractor telescope.

Important Note: This product was designed for an optimum 55mm back focus. (Distance from flange surface to film or CCD plane). If you use a CCD, be sure the spacing between flange and CCD is 56mm +/-2mm for best results."

 

Edited August 30, 2020 by Rustang