3 Minute Andromeda Galaxy Comparison

In October, I got this fantastic picture of the Andromeda Galaxy from Dell City, Texas with its Bortle 2 – 3 dark skies.  

Camera geek info:

  • Canon EOS 60D in manual mode, 179 second exposure, ISO 1600, custom white balance 3500K
  • Williams Optics Zenith Star 73 III APO telescope
  • Williams Optics Flat 73A
  • iOptron CEM40
  • Dell City, Texas Bortle 2-3 dark skies

I wanted to see what happened when I used the exact same setup and settings from my driveway in Friendswood, Texas with its Bortle 7 (much much brighter) skies.  My suspicion was that the picture would be all white.  

On my first opportunity to try the experiment, there was also a two days past full Moon in the same section of the sky.  As you can see, I did get an almost all-white picture.

I backed off to ISO100 to avoid overexposing the picture, but then I didn’t get near the detail that I got from the dark skies.

I didn’t know how much the overexposure was due to the near-full Moon and how much was due to light pollution.

Yesterday, I got the chance to try the experiment again with no Moon.  As you can see, at the dark skies setting, I again got an almost all-white picture.

I backed off to ISO100 and ISO400 to avoid overexposing the picture, but again I didn’t get the detail I did under darker skies.

All of the pictures in this blog post are unprocessed, other than being saved to a lower resolution format.  It will be interesting to see what I can get when they are processed.

How dark are your skies?

SiteBortleMoonExposure LengthISOResult
Dell City, Texas2 – 3No Moon3 minutes1600Gorgeous detail in M31, M32 and M101 visible
Friendswood, Texas7Near Full Moon3 minutes1600Almost all white picture
Friendswood, Texas7Near Full Moon3 minutes100M31 as a fuzzball, M32 and M101 not obvious
Friendswood, Texas7No Moon3 minutes1600Almost all white picture
Friendswood, Texas7No Moon3 minutes100M31 as a fuzzball, M32 and M101 not obvious
Friendswood, Texas7No Moon3 minutes400M31 as a larger fuzzball, M32 and M101 barely visible

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