Sizing a secondary mirror

[barx1963 (Malcolm)]

I am thinking of having a crack a building an 8" or 10" dob. I have tried reserching what size secondary to look at. Unfortunately most resources talk a lot about "desired size of illuminated field" and such like which is a little over my head.
Is there an easy way to find out a suitable mirror size for an 8" f4 scope?

Cheers

Malcolm

[Rod]

Hi Malcolm

This article might help you:

http://www.garyseronik.com/?q=node/8

Rod.

[OzEclipse (Joe Cali)]

There are many elements to consider including the tube diameter and focusser height.

This application lets you play with different configurations and then view ray traces

http://stellafane.org/tm/newt-web/newt-web.html

Good Luck

Joe

[bojan]

Also, you can try the old version:
http://www.soft82.com/download/windows/newt/
It's not a web/java application, it runs independently from internet connection.

[anj026]

Here is a table of sizes for different apertures and f ratios by Michael Lockwood.

http://www.loptics.com/ATM/diagonals.html

[barx1963 (Malcolm)]

Thanks Andy
That is precisely what I was after!!

Cheers

Malcolm