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Joe, nice job on ic1805!
You're right about the M16 shot, it's out of focus.
How are you using the KEF? With my 12"SCT, I usually align the grating lines in
RA, and then use the mount's .5x slow motion speed to jog the mount in DEC. Not
only do you look for the change in definition of the shadow's edge while
focusing, but the _direction_ that the shadow travels in as you move the scope
in DEC. While moving the slo-mo in one direction in DEC, the shadows will
move from L to R on one side of focus, then seem to "hang up" in movement at
good focus, then move from R to L when your past focus. And for a subject
of this size, focusing on a star about 1/3 from the field center is a good idea.
For a subject like a small planetary where I want the best resolution and
will probably be cropping the result heavily, I focus at the
center.
And as you probably know, with a C11 you should try
to finish your focusing with while turning the focus knob in the CCW direction
to help load the focusing mechanism with gravity. That will reduce mirror
movement due to settling during the exposure.
Thermal focus shift is a problem with an aluminum
tube SCT, and could be part of the problem with this M16 shot, but I doubt it
was the only factor in this case. It's pretty well out of focus.
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