Re: ATM Quality of Secondary Mirror

[btk@ix.netcom.com (Bill Marriott )]

You wrote: 
>
>Any tests of say 2.14 to 3.1 secondaries ? It would
>be nice to know what to expect !
>
>Bratislav 
>

In regards to secondaries, last Friday at the Chabot College Mirror 
Workshop, someone brought in an old Edmund Scientific 
secondary, rectangular, maybe 1" on minor axis, and wondered if we had 
any way to check how flat it was, as he was wondering if it was worth 
keeping, despite the limitations of a rectangular secondary.

Using a test flat we have,and a monochromatic viewer, we found the 
secondary's fringes were flat as a board, easily 1/10 wave. The lack of 
roll off on a rectangular flat suggests this was cut out of something 
larger after figuring.

Not to bad for an econo secondary.

I have a 2.25" eliptical in my 10" Newt., purchased from Edmond 
Sci. maybe 7 years ago. First thing I did upon recieving it was put it 
under the Fizeau interferometer at work, verifying that it did indeed 
meet its 1/8 wave call out.

Bill Marriott
Woodacre, Ca. USA
btk @ix.netcom.com