Focuser & Lense Questions?

morwim (Dan) · #1 31-07-2008, 11:21 PM

HI, I have a 2x 5" reflectors. one has a 1000mm focal length and the other has a 1400mm focal length. the longer one didn't come with a focuser so i removed the focuser from the shorter and fixed it to the longer hoping to get better results. but when i try and focus, i don't seem to have enough adjustment???? is this due to the difference in focal length???? Also i have 3 lenses, SR4mm / H12.5 / H20. When i look at Saturn, i can only focus in the H12.5 & the H20, the SR4 seems to have more times zoom but i cant seem to focus it at all. could this be due to the quality of the telescope itself???? Any advice would be much appricated. Thanks

TrevorW · #2 31-07-2008, 11:49 PM

the focal length is exactly that measure it then you'll see if you are not reaching focus with the focuser

morwim (Dan) · #3 01-08-2008, 10:04 AM

I thought as much Trevor, can anyone shed some light onto why i cant seem to focus the SR4.

rmcpb (Rob) · #4 01-08-2008, 02:40 PM

A 4mm lense in the 1400mm focal length will give a magnification of 350x. The theoretical maximum magnification of a 5" scope is about 250x on a stunner of a night and they will be VERY few and far between so the 4mm lense will just keep magnifying the blurring you get from overmagnification.

Cheers