MN66 Collimation-better but...

Hello,

So I tried to deal wuth the secondary tilt and that improved the unfocused
star pattern. At higher powers the image stays the same all around the FOV.
At low powers the image begins to change to an oval as it approaches the
edge of field.

Also, at high power, I notice that the extrafocal image shows some
miscollimation while the intrafocal image is very, very close to perfect.

Thanks for your advice.

Dan

Dan wrote:
Hello,

So I tried to deal wuth the secondary tilt and that improved the unfocused
star pattern. At higher powers the image stays the same all around the FOV.
At low powers the image begins to change to an oval as it approaches the
edge of field.

Also, at high power, I notice that the extrafocal image shows some
miscollimation while the intrafocal image is very, very close to perfect.

Thanks for your advice.



In a MN coma is only corrected for the in-focus position (for a FOV of
about 1.5 deg) that's why you get the effect you describe in the first
sentence. As for the second, my two only suggestions are to keep
refining the tilt of the focuser/secondary and, when you feel all you
could do was done, collimate the scope in-focus with high powers, 300x
and above on a bright stars. That's the way I use to do it (the 2/3
times I had to, that is).

Andrea T.

Andrea,

Thanks for the advice, that's just what I'll do.

Dan


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s.com...

Dan wrote:
Hello,

So I tried to deal wuth the secondary tilt and that improved the
unfocused
star pattern. At higher powers the image stays the same all around the
FOV.
At low powers the image begins to change to an oval as it approaches the
edge of field.

Also, at high power, I notice that the extrafocal image shows some
miscollimation while the intrafocal image is very, very close to
perfect.

Thanks for your advice.



In a MN coma is only corrected for the in-focus position (for a FOV of
about 1.5 deg) that's why you get the effect you describe in the first
sentence. As for the second, my two only suggestions are to keep
refining the tilt of the focuser/secondary and, when you feel all you
could do was done, collimate the scope in-focus with high powers, 300x
and above on a bright stars. That's the way I use to do it (the 2/3
times I had to, that is).

Andrea T.