To: atm{at}misterg.fsnet.co.uk (Andy Gray)
From: Mark Suchting 
Cc: atm{at}shore.net
Reply-To: Mark Suchting 




Andy ,

Your outer zones are  rolling up compared to a reference sphere touching
the 70% zone,  and  a mild hole in the middle  ( Ronchi lines are bowing
outward at the edge and bulging slightly in the centre ) .   There also a
kink near the edge which doesn't look good.  It would do well to do some
smoothing work, aiming for smoother straighter lines.    This would be good
practise in figuring, and you will end up with a smoother parabola.

~Mark

~Mark






At 01:09 AM 19/02/2003 +0000, you wrote:

>If someone would be good enough to look at the ronchi-graphs
>at:
>
>www.misterg.fsnet.co.uk/ronchi (just .jpg s, no html)
>
>and offer comment as to whether I need to get closer to a
>sphere before starting to parabolise, I would be most
>grateful!
>
>Mirror is ~F/6 7" (actually 180mm dia, 1100mm focal length)
>
>Grating is an inkjet print {at} ~110 lpi. All pictures taken
>inside focus at approx distances in filename (i.e. F-7mm...
>is approx 7mm inside focus, etc.)
>
>I've just finished polishing it out (passes laser pointer
>test under water).
>
>Many thanks,
>
>Andy
>
>Andy Gray, N.Wales, UK

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