What is this strange effect?

Hi, I'm new to imaging/processing and would like to know if anyone can explain what this strange haze is surrounding M31. Is this a processing issue or something I'm doing wrong at the camera? All the subs (about 20) were of varying lengths and iso's in a 400D. All the subs were also very short (<30 secs each) because I didn't get my shutter release cable for long exposures until after these shots were taken. Combined in MaximDL and raw images processed by Canon ZoombrowserEX. Thanks for any input/help!

Attached Image:

It looks like vignetting to me. The "haze" is either light pollution, or maybe it wasn't completely dark yet? What time was it when you shot these? Was M 31 still low in the sky?

Others here may be more helpful!

Steve

I agree that you are simply looking at normal vignetting on the center of M31. That, combined with processing choices, makes the glow stand out.

Your sky was a bit bright, probably the result of the moon, but perhaps light pollution.

From what I can see, you need to reduce the image scale by at least half. (In other words, you will be able to image only the central half or less of the galaxy with that field of view.)

What makes it look so dramatic is that you have vignetting, especially on the right part and the bottom of the frame.

You could try flat fielding the exposure some, and see if that helps.

ALex