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Re: [ATM] convex secondary
Thanks to Jim and Richard, I decided to refigure the 16 inch and go for the
Ritchey-Chrétien design. Since I have to repolish the big mirror, I will be
able to use it as a Hindle sphere for testing the secondary. I know it will
not illuminate the edge of the secondary but I have no problem to shorten
its RoC a bit to make the Hindle test then grind back to the good RoC.
But as I understand it right now, the Hindle null test will give the good K
of eccentricity for a cass secondary that use a primary of K=-1 (parabola).
In the RC design the primary will be corrected at K= -1.1
Now my question is: If I want to null test the secondary with the Hindle
test, can I just figure the Hindle mirror at K= -0.1 to compensate, then do
like I was making a cass secondary? If not (considering that the RoC of the
big mirror will be a tad shorter during the test than when it will go back
in the scope) is it possible to compute a good K of deformation to get a
perfect null ?
Jonathan
----- Original Message -----
From: "Jim Burrows" <burrjaw@earthlink.net>
To: <atm@atmlist.net>
Sent: Monday, February 28, 2005 7:37 PM
Subject: Re: [ATM] convex secondary
> At 2005-02-27 02:04 -0500, Jonathan Lavoie wrote:
>
>>I know the radius of curvature for the 4 inch secondary will be 34.5 inch
>>and I know that it has to be an hyperbola but I didn't find the amount of
>>correction that needs to be done. The primary is an F3 parabola amd I will
>>not change its figure. So what figure do I need for the secondary to
>>optimize the system for imaging with a Digital SLR like the Canon 300D ?
>
> Texereau, Eq. (31) & (32), p. 145, gives the equations for the
> deformations (conic constants) of "Stigmatic mirror combinations". Hey,
> if you want to go whole hog for an imaging scope using them mucho $
> Canons, deform the primary also to make an RC - Eq. (42) & (43), p. 147
> (lotsa fun and a real challenge).
>
> -- Jim Burrows
> -- mailto://burrjaw@earthlink.net
> -- http://home.earthlink.net/~burrjaw
> -- Seattle N47.4723 W122.3662 (WGS84)
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> ATM mailing list http://www.atmlist.net/
>
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