There have been many threads on which scope/eyepiece combo to use for wide field. Being a wide field junkie I've been on my own search to find affordable wide field enjoyment with a telescope. Enter the TS 2" FF....have thought about this one on and off for a few years. Teleskop Express used to call this for visual and AP use, but dropped the visual part for some reason. CN member doctodub? or is it doctordob....can't remember, mentioned using it for visual and how well it worked in a very recent thread, so I bought one. To make the decision easier the price used to be 225Euro's but was down to E155....the buy button was pressed.
I have 3 scopes I like for WF. 102mm f5 Celestron with GSO Crayford upgrade, 80mm f7.5 Achro used as a WF on my 6" f12 Refractor and a 60mm Sharpstar ED.
The specs for the flattener say for the 102 f5 I need 118mm light path for the FF to work, 113 for the 80mm and 128 for the 60ED.
For this I used 4 eyepieces, Pan 41 Pan 35 ES 34 68 and Agena Astro SWA38. Did comparisons with and without the FF. The Diagonal is a GSO 2" Dielectric. I measured the light path of this diagonal to be 113mm....a lucky number as it happens!
After a number of nights my result so far is:
The winner is the 80mm + FF and the Pan35. Pinpoint to the edge, very nice view at 4º TFOV. In the same scope with FF Pan 41 vignettes badly, ES34 has edge issues from 80% out, ditto the 38SWA. Take out the FF and the Pan 35 is still the best view 80% out with a bit of FC visible.
4" f5....no real difference for some reason with or without the FF....best is the Pan 41. Widest with nearly pinpoint stars at the edge. This is probably more to do with the lack of magnification but good is good. Next the 35, good to 80% out. ES34 good to 70% out and 38SWA bringing up the rear and not worth using, seeing as the Pan41 is so good.
Haven't got around to the ED60 yet....more to come. I need to muck about with spacing for the 4" f5 too...118mm might not be the best.
So far I'm very happy with the TS 2"FF as I really bought it to use with the 80mm f7.5. Turns my cheap preloved Achro into a nice WF scope, as long as I stick a Pan 35 in the focuser. The focuser being the weak point of this scope. The usual pincushion is evident, not that I'm bothered by that.
Photo's of the scopes in question and the FF on the diagonal.