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markarian
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21 minutes ago, carastro said:

Glad you have got to the bottom of it, and thanks for coming back to us.  It was certainly a mystery, but what are you going to do now?  Not use the MPCC?

Carole 

Definitely not going to use it - and it seems the 10 inch newt really doesn't need it. As Louise says - the sensor size probably means I gets away with it.

In fact the MPCC was doing really weird things to the stars - even at the correct spacing. Not sure what was going on there. It worked fined for the 8 inch newt.

Edited by markarian
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Don't know if it will show in the corners or not - depends on seeing and guiding, but

F/4.8 10" Newtonian has diffraction limited field of about 2.45mm. Atik 460Ex has diagonal of 16mm so in effect only about 15% of field is diffraction limited.

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1 hour ago, markarian said:

This I took  last night shows much better stars without the MPCC than with surprisingly. Even stars in the corners look pretty good.

 

It's actually not that surprising :D

Level of coma is - I would not expect it to be so small, and have a look at collimation - it looks like it's a tiny bit off - stars in bottom left corner look really good, and in top right more coma shows (you want to balance it out to be about equal in each corner).

Star shapes on the other hand tend to be worse with Baader MPCC on fast scopes - due to spherical aberration introduced, so no wonder stars look tighter in center field without MPCC.

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