Monthly Archives: November 2022

3 Minute Andromeda Galaxy Comparison

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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

3 Minute Pictures from Dell City – October 2022

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A few weeks ago, we took my telescope and tracking mount on a road trip to our favorite Air B&B in Dell City, Texas.  My telescope and I enjoyed the dark (Bortle 2-3) skies.

Here are some three minute long exposure images I was able to get:

Andromeda Galaxy (M31) plus two satellite galaxies (M32 and M110).  The Andromeda Galaxy is the nearest large galaxy to our own, at 2.5 million light years away.  Its apparent size is 3.167 degrees by 1 degree.  In comparison, the Moon has an apparent size of 0.52 degrees on average.  The Andromeda Galaxy filled the screen on my camera – this image is not cropped at all.  It has an apparent magnitude of 3.44. 

Triangulum Galaxy (M33).  The Triangulum Galaxy is the third largest galaxy in our local group, after the Andromeda Galaxy and the Milky Way.  It’s 2.73 million light years away, and its apparent size is 1.2 degrees by 0.7 degrees.  It has an apparent magnitude of 5.72.  

Crab Nebula (M1) with Mars.  M1 is the remnant of a supernova observed in 1054.  It’s located in the Milky Way, 6500 light years away.  Its apparent size is 7 arcminutes by 6 arcminutes, and it has an apparent magnitude of 8.4.  Mars, of course, is the fourth planet in our own solar system, and the brightest object by far in the image.  

Eye of God (or Helix) Nebula (NGC7293).  The Helix Nebula is planetary nebula – the gases expelled from a star before it becomes a white dwarf, lit up by that star.  It’s located in the Milky Way, approximately 655 light years away.  Its apparent size is 25 arcminutes, and it has an apparent magnitude of 7.6.  

Orion Nebula (M42).  The Orion Nebula is one of my favorite objects in the sky, and one I’ve photographed before.  It’s a diffuse nebula, a cloud of dust and gas that is forming new stars.  It’s located in the Milky Way, about 1344 light years away.  Its apparent size is 65 by 60 arcminutes, and it has an apparent magnitude of 4.

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’m really looking forward to photographing these from my suburban driveway to see how the images compare.  It will be interesting to see if I get a white screen (pure light pollution) at these settings.  I’ll let you know!

I’m also looking forward to learning how to stack together a sequence of images with PixInsight to see what an hour plus image looks like.  I’ll share that when I figure out how to do it!