Quote:
Originally Posted by astro744
I did the same with a 10.1” f6.4 (Suchting) with 2.1” and 1.83” secondary. Installed the 2.1” for the same reasons but also I prefer less magnitude drop at the edges in my wider field low power eyepieces. I can interchange them fairly easily.
I got the best view ever of Saturn in a 16” f5 (Suchting) but with a 2.6” secondary. Almost like having a 16” refractor. However I felt the low power wide field views were noticeably dimmer at the edges. If it were mine I’d probably go for a 3.1” secondary at least maybe 3.5”. Note other factors such as tube diameter, tube thickness and focuser height come into play, (also use of Paracorr).
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This was one of the differences I noticed when switching from my 18" F5.6 to my 18" F3.5 scope, the illumination drop off in the slower scope is significantly more acute.