Re: [ATM] mirror box baffle question

[Alexis Cousein <al@sgi.com>]

Michael Lindner wrote:
> Dave Smith wrote:
>> Can anyone comment on the diameter of a baffle in the
>> mirror box. Should it be the approximate diameter of
>> the mirror itself? If so, are there issues with having
>> such tight tolerances between the optical path and the
>> baffle?
> 
> Good question. If your goal is simply to baffle, then it should be about 
> the same size as the mirror. 

If over the mirror (this may cause troubles for any air circulation
around the mirror, especially with air forced by a fan setup, unless
the baffle is *only* over the mirror, but these baffles usually serve
to hide whatever is *around* the mirror).

If it's placed higher up, you should take into account the size of
the fully illuminated field you have, and whether you want the drop-off
of illumination that occurs by light missing the secondary to be
exacerbated by the baffle. If you don't want your baffle to vignette
a true field of view of around 1°, then you should make sure that
lines travelling from 0.5° away from the optical axis hitting the
edge of the primary don't hit your baffle. Divide degrees by 57.3
to get radians and use sin(x)~x if x is in radians and small ;).

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