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Prism vs mirror diagonal in APQ's

Started by kcolter, 02/28/2005 04:29AM
Posted 02/28/2005 04:29AM Opening Post
I have been told that the original APQ objectives and tubes were configured for the use of a prism diagonal as opposed to a mirror diagonal. The more recently released APQ's have been suitable for use with a diagonal such as the AP Maxbright. Is there something about the APQ objective that "needs" the additional glass of the prism diagonal to give the optimal image? Is there a difference in length of light path when the prism diagonal is used compared to the reflective diagonal? Is there much additional refraction of light occurring in a prism diagonal? Can someone "shed some light" on this issue?
Posted 02/28/2005 09:17AM #1
Kim

usual the APQ have been designed to be used with the Zeiss M44 diagonal prism. If you use in this modells a stardiagonal mirror, you will see quickly the differenc,e by getting color and some sphericla aberration. Recently I have seen also so APQ which have been designed for mirror use, not prism use.

There is no info on the optics which is for what designed, only a quick startest will show it

best wishes
Markus

clear skies

Markus Ludes
APM-Telescopes/Germany
Posted 03/02/2005 12:10PM #2
Kim
I have for several years read indirect references to the supposed fact that prisms are preferred.

It could well be an "urban myth" amongst Zeiss owners perhaps it is a fact but no where have I read anywhere a technical reference from say a Zeiss information leaflet!!

What Roland discusses below is of some interest to me.
As is what Markus refers to.

Another perhaps "urban myth" is the discussion about oil leakage and the effects on star tests. Again it was talk but no real quantitative info.

As Markus suggests the answers may be known by Mr Baader and his optical staff. Or as Paul suggests Dr Lalk

Perhaps we should ask them for an answer.

best wishes

Kevin