A few weeks ago after taking some photos of Jupiter, I changed my setup to do some long exposures on an easy target: a globular cluster. Unfortunately I forgot to note down the name of what I had photographed! So a few weeks later when I found the time to process the images I was at a loss to identify what Messier object it was. However, after an evening of matching up stars surrounding the cluster and I was able to correctly identify it as Messier 3.
Globular Cluster – Messier 3 (Benoit Guertin)
The above was taken with my Skywatcher 80ED and Canon 80D. It is a stack of 27 x 10sec exposures at ISO3200 on an unguided and roughly aligned mount.
Looking at my archives I found that I had imaged M3 about 10 years ago with the same telescope, so I decided to align both old and new image and see if anything would stand out. And to my surprise, spotted one star that appeared to have shifted. To help identify the star I colorized one of the photos and subtracted from the other (done in GIMP). All the stars within the field of view lined up except this one; the two colored spots are not aligned!
High PM Star BD+29 34256
To be sure this wasn’t on an error on my part I did a bit of research and found it to be a know high proper-motion star BD+29 34256.
It’s not everyday someone with amateur backyard astronomy gear can show how a star has moved in 10 years.
In a telescope globular clusters are more interesting to observe than your open cluster because they have a distinctive shape. Globular clusters are odd stellar objects; they are spherical clumps of stars that actually orbit our galaxy’s core. But not the way you might think; they don’t orbit in the galactic plane, but often perpendicular to it! This is not unique to the Milky Way, most nearby galaxies have their share of globular clusters.
Messier 53 is a nice example of a globular cluster located in the Coma Berenices constellation. It also happens to be one of the more distant globular clusters from the Milky Way.
Globular Cluster Messier 53
Canon 400D (ISO 800)
19 x 60sec
For this one I decided to try my luck at 60sec of exposure time, and the results aren’t too bad. I did have to throw out a few shots due to periodic error causing elongation in the stars. Also during the stacking a used a sigma 2.3 value to discard anything that fell out of standard distribution to reduce the impact of the few bad images.
Messier 13 Globular Cluster
M13 Globular Cluster – Benoit Guertin
Equipment: SW80ED, Canon XTi
Imaging: 29x15sec ISO800
The above image is a crop of the original. In the full frame image, galaxy NGC6207 (60 million light years away) is faintly visible on the top of the image at 1 o’clock from M13. As a reference M13 is 22,000 light years away.