[ATM] convex secondary

[Jonathan Lavoie <atm@lavoielactee.net>]

Hello,

A fiew years ago I built 2 telescopes. One 10 inch F6.25 Newt and a 16 inch F18 Gregorian. Now I want to shorten the focal length of the Gregorian. I need to polish a 4 inch convex mirror that will be 11.5 inch inside the primary focus. This will give an F9 system.

I know the radius of curvature for the 4 inch secondary will be 34.5 inch and I know that it has to be an hyperbola but I didn't find the amount of correction that needs to be done. The primary is an F3 parabola amd I will not change its figure. So what figure do I need for the secondary to optimize the system for imaging with a Digital SLR like the Canon 300D ?

Jonathan
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