Re: [APML] Diffraction spikes with a refractor

[Philip Perkins <philip@astrocruise.com>]

>The most likely is the OAG, either the edge of the corrector / reducer lens
>or the pick off prism or some other object in the light path inside the OAG.


I would agree that this is due to the light cone striking something at the 
edge of the field such as the edge of the focal reducer (which was used in 
this case) or the pick off prism.  This effect is not seen too often 
because it needs a bright star to be positioned at some critical point very 
near the edge of the field.  Since this star is not very near the edge of 
field it seems that the pick off prism is a likely candidate.  I see the 
same effect sometimes (to a much lesser extent) with bright stars near the 
edge of field when using my AP 155 EDF with field flattener in place.

--Philip

Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com


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