The well-known galaxy NGC 4565 or the “Needle Galaxy” is seen edge on from Earth at a distance of around 50 million light years. It is also a popular imaging target and so I am in the process of imaging it with the 16″ telescope at Orion’s Belt Remote Observatory What is not as well known are the thousands upon thousands of other objects that are also contained in this 45 arc minute square of space! This is not something I am discovering for the first time but since we had a superb night of seeing when this image was taken I decided to look a little more closely at the “background” of my image. I think this activity is very important in general for anyone imaging out there because you might surprise yourself with what you find. And to be fair, you never know if perhaps there is something”undiscovered” in your images! So the steps I take to uncover the “hidden gems” in my images are as follows:
- I take my image and open it in the program I use for image processing, i.e. Pixinsight
Plate solve the image. To do that you do what it says in the caption and image above.
- After you run the script I just leave the image open and then go to the next step which is to run the annotation script. That’s the one that tells you what’s in there!
The result is seen below:
Now let’s look a little more carefully at this:
A little more magnification shows there 5 obvious named galaxies but one I circled which was not named after I ran the script the first time.
The small fuzzy patch in the center here is not dust or some other artifact but is actually “IC3571”, an irregular galaxy. Quite dim. It is around magnitude 17-18. Remember this is a green filtered image so my guess is a lot more information would exist with an unfiltered exposure! As I look around the image I see all of the galaxies named are of the “IC” catalog type. This stands for “Index Catalog” and is a supplement apparently to the well known “NGC” catalog or “New General Catalog” which was produced at the end of the 19th century! Since then the explosion in data acquisition over just the last 20 years has produced countless catalogs and databases which we now have access to! So back to the image. I was very curious why the galaxy I circled in white in the 2nd image above was not designated as it was obviously brighter. I went back to the image annotation script and realized there was a galaxy catalog database that was not checked!
So what is this? “PGC” is the “Principal Galaxies Catalog” published in 1989. The “Lyon-Meudon” extragalactic database or “LEDA” was created at the Lyon observatory in France in 1983 and apparently the PGC catalog was based on LEDA. In the early 2000’s the PGC/LEDA database expanded to become “HyperLEDA” or literally LEDA on steroids! It’s basically an extragalactic database for astrophysical research and contains data on about 2 million galaxies! We’re light years away from the old “NGC” days!
After running the annotation script a second time with the PGC data included, the result was this:
The galaxy I had circled in my original image that was unnamed is now identified as “PGC42060”!
More information about this region can be investigated on the HyperLEDA database website. That will keep you busy for awhile!:
But that’s not all! What else could be hiding in the background? You can also go to the well known astronomical database “Simbad”:
You have a number of options from here. If you enter the name of the principal object in this case NGC4565 and the size of the field (50 arc min) you will arrive on a page with a list of hundreds of identifiable objects. Not only galaxies, but planetary nebulae as well! If you go to the top of the Simbad home page, you can click on the second tab to the right labeled “Aladin”. There you can access a digitized sky survey image of your field that shows you where all of these objects are located:
And you thought this was just about “pretty pictures”! Enjoy hunting for the “hidden gems” in your images!
Thanks for reading!