|
f/4.66 on my 10" newtonian.
If I upgrade sometime in the future , f/3.5 - f/4 will be my preference.
I don't fancy having to climb a wobbly tall unstable ladder in the dark while alone to look through the eyepiece and shorter "tubes" are stiffer than long ones.
I also like a nice wide fov and the gain in photograhic speed (same criterion as you might use if trying to shoot under dull lighting (a fast , low f no lens will all you to record the image faster on film or the chip , whereas a slow (higher f number say f/22) requires a much longer exposure to capture the image on the same speed film, though it will give a deeper in focus field).
|