[APML] Question on vignetting

["Bradley" <bhope@thorngarden.net>]

Morning, everyone;

Got a chance to go deeper with the Orion Nebula and now, for the first time,
I'm seeing a lot of vignetting I've never noticed before. Perhaps not the
best image to use to demonstrate it due to the trailing, but it shows the
vignetting the best.

I've checked the RA drive at a few steps above guide rate after putting the
scope back in approximately the same position and listened carefully...and
heard faint little crunchie sounds...so I get to take the scope down and
tear into the RA drive. Only seems to do it in one section of the sky so I'm
hoping it's just an "illegal alien" in the worm gear. And "DUH ME", I didn't
think to check polar alignment after hanging an extra 20lbs + on the scope
(Orion ED80, piggyback setup, 7 lbs of counter weight, Pixcel 237) so I got
a bit of field rotation going on as well. Also, the framing within the
vignetting is off a bit, M43 could have been a bit higher and I'd a brought
up more of the nebulosity beneath M42. I'm learning, and dealing with
issues..but, sadly, this will probably have been my last chance at M42 this
year. I'll be able to salvage some of what I shot night before last, but it
isn't going to be as good as it could have been...if I hadn't had the
trailing.

What I'd really like to ask is if the amount of vignetting I'm seeing is
normal?? Optical train is 10" SCT (2500mm at f/10), Meade microfocuser and
rear cell adapter, Meade .63 focal reducer, Meade T-adapter, 35mm camera.
Can the vignetting be reduced some by reducing the optical train..ie, by
removing the Microfocuser perhaps? Or by a different placement of the focal
reducer......or is this about what I should expect?

Clear, dark and steady skies

Bradley

Thorn Garden Observatory
http://astronomy.thorngarden.net

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