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Hey folks,
I'm just a beginner, but I'm intrigued with how you guys collect image
data over time. I often hear 20+ hours of data or more implying that a
number of exposures have been taken of the same subject over many days,
months, even years to build image data. I assume that this requires
detailed notes as to exposure times, focal length of the scope being used,
camera position, FOV, or additional optics in the train, i.e filters,
flatteners, focal reducers, etc. In these cases, how critical is the
geo-location of the imaging scope in terms of latitude? Or is this
automatically worked out because the celestial object does not change in
position relative to the celestial sphere? Additionally, what methods are
used to accurately position/orient the rephotographed object in the frame to
ensure it will align during the stacking process with previously
photographed images? Is this even critical given the large CCD areas some
of you guys are using?
The other question I have regards image processing. My stacking programs
are K3CCD and Registax. I usually follow up with additional processing
using Adobe Photoshop v.7 to enhance the image and pull out the detail not
evident in the original, stacked image. I'm having problems in that I'm not
able to control the dynamic range of the image. This leads to burned out
centers of galaxies or bright nebula and loss of detail e.g. M31 and M42.
Back in my film days, I could control such issues by dodging and burning
selected problem areas during the printing process. In CCD photography,
this technique is not practical since the adjustments need to be done during
exposure. So, simply -- How do I keep my centers from burning out? Is this
corrected during the processing stage or is it controlled during exposure?
or both. If so, how?
My current imaging setup uses a Takahashi TSA102 with a flattener/reducer,
Sbig ST2000XM camera all on a Losmandy G-11 mount. I'm aware of the 8bit
limitations with Photoshop v.7 and plan to upgrade to CS2. Also, I save my
images as jpegs prior to post-processing. I realize this is part of the
problem, since jpeg compression destroys a lot of available detail that
would otherwise be saved with a fits file.
I have several books about using PS as an astrophotography post processor,
but they are tedious to work through.
Your comments and suggestions are appreciated.
V/r
Scott Busby
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