-THREAD MOVED TO EQUIPMENT DISCUSSIONS-
Can someone please assist with working out secondary mirror size?
The scope is 200mm F5 (1000mm). I believe the current secondary is 55mm and since it needs replacing anyway I figured a smaller secondary would be better for contrast.
One big factor seems to be the size in diameter of the focal plane. This is what's got me stuck.
A 45mm secondary will reduce the obstruction from 27.5% to 22.5%. That's got to be good!
Using a 32mm TV plossl the current 55mm secondary seems to fully illuminate this eyepiece to perfection (using some calculator) but how much smaller can I go with a reasonable loss in magnitude? These calculations are doing my head in.
If i can get better contrast for higher magnification but still use my lower mag eyepieces with little effect then great -
