Examples of Mistakes

Hi all,

Anybody know of a webpage or book where I can find examples of mistakes of astrophotography. (Yes, I know I can look in imy own album if all I want to see is "mistakes.") What I am looking for are examples of bad polar alignment, or bad seeing, or bad focus. How does one tell one from another? When is the less than good image the result of polar alignment error, and when is it bad tracking (or one of the other mistakes one can make)? What is the difference in a finished picture between out of focus and bad seeing? and How does one tell with a finished slide?

Alex

Alex,
I have a few! *L*
Here is one with bad focus...
http://members.cox.net/ecdon/Rosettecomb.html
Note the overly bloated stars. I also had dew/frost starting to build up on the objective on my Astroview 120 refractor.
Here is another one taken the same night.
http://members.cox.net/ecdon/horseNflame.html
Note the bloated stars (focus) and thier oblong shape (star trailing due to poor polar alignment).
Bad polar alignment will make the stars, starting from the edge of the photo, trail in a circular motion, sort of like a bullseye. The longer the exposure, the more the trailing creeps towards the center of the photo.
Don Spencer