Re: [ATM] convex secondary

["Jonathan Lavoie" <atm@lavoielactee.net>]

Why wouldn't the secondary be 4", I tought the only difference between 
Cassgrain and RC was the figure of both primary and secondary mirrors?

I know anything about interference testing, does it need special equipment? 
How accurate is it?

About grinding and polishing twice the primary, it does not scare me because 
there is not much glass to remove each time and the first polishing does not 
need to remove 100% of tiny pits at the edge. If this method of null testing 
is doable and has good fiability I think I would go for this technique.

Jonathan

----- Original Message ----- 
From: "Mike Lockwood" <melockwo@uiuc.edu>
To: <atm@atmlist.net>
Sent: Tuesday, March 01, 2005 10:54 AM
Subject: Re: [ATM] convex secondary


> Hi,
>
> Oops, I just realized that if you've changed to an RC design the secondary 
> will probably not be 4" in diameter.  You could still make a test plate, 
> just of a different size.
>
> Mike
>
> Mike Lockwood wrote:
>> You might also consider making a 4" diameter concave test plate, and 
>> figuring the secondary to match it using interference testing.  This way 
>> you can avoid grinding/polishing the 16" mirror twice.
>
>
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> 

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