[ATM] Testing a flat

[Otterstedt at t-online.de (Heiner Otterstedt)]

Hi Adam,

you wrote:

>"If you set the flat at 45 degrees in front of your mirror, in contact
>with it, then go back to radius of curvature point. With careful
>adjustment you will see yourself reflected larger and larger (eye). If
>from this position you can use some very small torch bulb (no reflector)
>to illuminate the flat, which will in turn reflect the light back, into
>an eyepiece you have placed next to the bulb, examine the image. If it's
>a good image, your flat is good enough, in fact excellent. If the image
>is totally haywire, bad luck."
>  
>
I think, you should better do a real "Ritchey Common Test", which is a 
Foucault Test against a good
sphere with your test candidate in the light path.

See the archives for details on the Ritchey Common Test:
http://astro.umsystem.edu/cgi-bin/search_atm.cgi?query=Ritchey+Common+Test&show_context=0&results=0

Good luck with your flat!
Ciao, Heiner