Thanks for helping me out Bob. If 15:1 is ok, can i use 10mm glass for a 150mm diameter mirror?

Will this make it harder for me to make this mirror, being a first timer?

The tube i have is 220mm diameter fiberglass and 700mm long. I will have to add a bit to the end if i have worked out 6" x f/6 to have a total focal length of 36". Do you think f/6 is the best mirror for a first timer to try grinding?

If the glass is thinner, do i need as much room around the mirror or can i get away with a 7" or 178mm diameter mirror in this tube?

This will give 42mm or 1 5/8" space inside the tube. Will this larger mirror give be a much better picture?

Is there a formula to work out the focal length in metric?

Once again, thanks for helping out another beginner.

• thicknes - bobmay - August 9, 2002 - 18:59 UTC