[ATM] what is strelh ratio and how do I mount the spider

["David Williams" <dwilliams1128@earthlink.net>]

Hello to the ATM list

I heard a lot about the strelh ratio and I have wondered what that is.  Is that something like the wavefront error measured in lambda, but just slightly different?  


Also I have a polished mirror (20" F5 1"thick thin mirror), a mirror mount made out of plywood, an eyepiece focuser, the sonotube, and the secondary (mirror that is 3.1 minor 
axis) and spider are on the the way in the mail.


This is what I have :
primary mirror
primary mirror mount
eyepiece focuser
sonotube

This is what I don't have but is on the way :
secondary mirror (3.1 inch minor axis)
and spider

My question is this:  Given that the sonotube is 8 feet, 3 inches long and the focal length of the primary mirror is 100 inches, where should I place the eyepiece holder (focuser), spider, and primary mirror mount?
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