Re: Re: ATM My TDE

[<tomjan@ozemail.com.au>]

I've only ever seen it on a 6" F15 that I did acouple of years back. But I'm no expert so it could have been an extream example.

Thomas.
www.tjanstrom.com
> 
> From: "Herb Kasler" <h.kasler@attbi.com>
> Subject: Re: ATM My TDE
> Date: 10/12/2002 4:05:17
> To: <david.a.stevens@gm.com>, 
> 	<atm@shore.net>
> 
> 
> 
>    Dave,
> 
> Can you see any hook at all on a Ronchi test? At F/3.9, the Ronchi lines
> should be straightening out quite a bit towards the very edge of the mirror,
> so a really significant TDE should give you a pretty easily noticable hook.
> Alternately, a star test on a bright star with the uncoated optic should
> give you a characteristic pattern if the very edge is siginificantly long.
> If these two tests don't indicate any problems, then I don't think that I
> personally would get too worried about not seeing a diffraction ring all the
> way around the mirror on the Focault rig. I certainly never saw such a ring
> with my 16" f/3.9 mirror, even when I masked off the edge to a spot where
> the figure looked perfect. Perhaps the ring gets harder to see if the focal
> length of the optic is very short. Experts?.....
> 
> 
> Good luck,
> Herb.
> 
> 
> 

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