Re: [ATM] Super compact Houghton camera

["vladimir sacek" <vla@toast.net>]

Chris Dalla Piazza wrote:

> One thing that I was warned about from someone else that made one is the
> collimation.  He wouldn't specify which degree of freedom or if all 
> combined
> were troublesome.  I have heard that centering the corrector lenses is
> important and that misalignment can lead to astigmatism.

I don't have formula, but the raytrace suggests that if you keep corrector 
decenter bellow 1mm and tilt less than 0.1 degree, it should do fine (seems 
that the second lens element is more sensitive to both tilt and decenter, by 
nearly a factor of 2). Btw. it is the coma that will show as a result of 
misalignment.

Once the corrector is aligned with the telescope axis, the mirror has its 
regular sensitivity, as if the corrector is not there - for the field 
center. The difference is that there wouldn't be a good spot shifted 
somewhat off the center, due to the beam picking up the coma at the 
corrector, for which that beam would necessarily come at an angle.

Once both corrector and mirror are aligned, the diagonal is quite 
insensitive to its misalignment coma-wise, since there is no coma. The only 
problem that could arise from a significant diagonal  misalignment is image 
tilt.

Vlad 

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