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My current Dob scope is an 8" f/7.5 Newt with a 1.25" focuser. I want to upgrade to a 2" focuser but I believe my diagonal is too small. What size diagonal should I use, or how do I calculate the correct size, for an 8" f7.5 Newt?
Gabrielle See Far Sticks: Elita 103/1575, AOM FLT 105/1000, Bresser 127/1200 BV, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS 100/1000, Vixen SD115s/885 EQ: TAL MT-1, Vixen SXP, SXP2, AXJ, AXD Az/Alt: AYO Digi II, Stellarvue M2C, Argo Navis encoders on both Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102 Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Tak prism, TAL, Vixen Eyepieces: Antares to Zeiss (1011110) The only culture I have is from yogurt
I measured my secondary mirror by guestimate and got 1.44" minor axis diagonal which, according to the online telescope design websites, is plenty big enough to fully illuminate a 2" EP. So now I'm shopping for the new 2" focuser.
Cheers,
JT
PS, it's not easy measuring your secondary mirror when you don't want to disturb it inside your OTA... jt