Leroy Guatney a écrit :
>
> Not being an optician enough to understand the astigmatism argument you make,
> I have some other thoughts about this subject.
>
Don't worry, I am not too, otherwise I guess I would have solved this
thing a long time ago :-)

> The Corrector plate has alignment marks. Shouldn't there be some on the
> secondary too if its orientation was important?
>
No, I could not find any.

> Also, presuming that your secondary is centered around the centerline of the
> optical path, spinning it would be no different from viewing through the
> eyepiece (allowing for a star diagonal changing the path by 90 degrees) at
> different position angles oriented on the back of the primary mirror cell?
> Same as changing the angle of your star diagonal aspect to the OTA.
>
> In other words, just using an eyepiece, no diagonal, and drawing a clock face
> on the back end of the telescope, rotating the secondary 90 degrees would be
> no different than aligning your body to the eyepiece from the 4 o'clock angle
> compared to the 7 o'clock angle.
>
> Thoughts?
>
> Leroy Guatney
Not if say the lens has some astigmatism and that the secondary mirror
corrects it (for example). The final image can become acceptable, but if
you turn the secondary mirror 90°, both astigmatisms would then add
instead of substract and the image would be terrible (which it is in my
case). Just the current idea I have about this now, not to say that this
is the true problem. I don't know exactly what is causing what I see and
would like to understand this argument about rotation of optics as being
important (preferably from somebody working at Meade or Celestron).
Maybe this has already been discussed on this list, does anybody know
about this ?
Alain

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