Re: [ATM] secondary size dillemma

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

List:
Would the 1/2 mag loss at the edge be compensated by the higher sensitivity
of the eye in the marginal fov? I bet that the eye sensitivity varies more
than a half magnitude.

John:
> Does anyone know why an undersized secondary always seems to increase
contrast in the
> image? I can understand if the small secondary is vignetting away a TDE or
un-blackened bevel,
> that would certainly be an improvement. Or is it just the smaller
obstruction? Does going from
> 19% to 16% really make enough difference to the diffraction to give a
noticeable contrast
> increase?

For the effect of central obstruction, see:
   http://www.laughton.com/paul/rfo/obs/obs.html

/AtM

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