A Final Challenge
This observing program was challenging for a number of reasons. Chief among them was the size of many of the objects — especially the Lacertae galaxies. Ironically, the last photo I worked on was the most challenging. I chose to try and photograph PG 1553+113, a 15th magnitude galaxy in Serpens. The Slooh scopes I am using have a number of star catalogs from which to choose a target — but none with the PG designation. Unfortunately, there were no other object IDs to choose from. (In a number of cases, I was able to use a PGC or UGC identifier to locate an object with an otherwise obscure catalog listing.)
Slooh’s other way of target choosing is to use RA and DEC. I had the coordinates from the program instructions and directed a Slooh scope to that spot. But then I ran into another problem. My “go to” plate solvers (Nova Astrometry online, and Pixinsight on my Mac) can find PGC or UGC numbers, but no PGs. Sky Safari was of no help either. I did some more investigation and discovered a source related to SIMBAD called Aladin. I began in SIMBAD and did a basic query on PG 1553+113. SIMBAD returned a page of arcane references and but also a link to an Aladin photo. When opened, it marked the location of PG 1553+113 with a small blue + sign. I took a screen shot of my photo and the Aladin photo, tried to make them the same size, and put them next to each other. Here is a link to that composite (opens in a new browser tab). Notice the arrows in each frame. These show that the two photos are of the same area of the sky. I zoomed in on the blue + sign in the Aladin photo and did the same with my photo. Here is a link to the zoomed in composite (opens in a new browser tab). Notice that the blue + sign in the Aladin photo actually obscures PG 1553+113. But as seen in my photo, without the + sign, the galaxy is located as if it were one corner of a triangle. Some “plate solve!”