Problem reaching focus

keppar (Graham) · #1 06-10-2008, 08:04 AM

I connected my 40D using a 1.25" t adapter to my Mengrez 90 refractor using the prime focus method .Why cant I get focus on the moon ?
Yet using the scope with a 20mm eyepiece I can get focus. I also get a lot of vignetting (I hope a 2' adapter will help this). What am I doing wrong ?

RB (Andrew) · #2 06-10-2008, 08:29 AM

You will need an extension tube to bring the 40D into focus.
Also using a 1.25" adapter will cause vignetting on the 40D chip.
Use a 2" adapter instead.

montewilson (Monte) · #3 07-10-2008, 04:42 AM

Hold a piece of paper at the back of the scope to find where the focus is at infinity. You can do this during the day looking at a distant object.

Also try to be more descriptive in your thread titles - you will get more responses.

iceman (Mike) · #4 07-10-2008, 04:58 AM

Hi Kepper,

to IIS.
I've edited the thread title to be more descriptive but it sounds like RB is on the money with his suggestion.

keppar (Graham) · #5 08-10-2008, 07:09 AM

Thanks Fellas
Obtained focus (just ) with camera mounted directly into eye piece have ordered extension tube could not get focus using 90 Diagonal do you know why