Re: [ATM] first light on a Lurie-Houghton

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I don't think so. We measured pretty carefully the angle of the corrector plates, and it was right at 90 degrees, as far as we could tell. It's something else, and I am not sure what. 
Perhaps we calculated the curves wrong all together, perhaps the glass wasn't what we thought it was. Perhaps the convex ones weren't as close to the concave ones as they should be.
Guy

Chris Todd <christopher.todd@gmail.com> wrote: Guy,

I was wondering whether you had determined the cause of the image
aberrations in your Lurie-Houghton.  Was it tilt in the corrector?

Chris

On 8/14/07, Guy Brandenburg  wrote:
> Then this might be it. Hope it is, because trying to get the actual parameters of the glass would be a real pain in the neck, and will risk breaking the corrector plates.
>
> vladimir sacek  wrote:
> Guy Brandenburg wrote:
>
> > I could tell that the corrector plates were not truly parallel to the
> > primary, but didn't have the means to fix and adjust that at the time.
>
> The only thing about Houghton corrector that has very tight tolerances is
> its tilt. It is roughly ten times as sensitive to it as Schmidt corrector,
> whose wavefront error in terms of the tilt angle t (in radians) is given by
> W=tD/48F^3, D being the aperture diameter and F the mirror focal ratio
> number.
>
> As little as 1/10 degree tilt would produce some 0.6 wave of centerfield
> coma (equivalent to somewhat over 1/3 wave of spherical aberration).
>
> Vlad
>
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Guy Brandenburg, Washington, DC
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or else 
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