Updated: Oct 3, 2021
What is Plate Solving?
Plate Solving, as it relates to amateur astrophotography, in its simplest form is taking a picture of the night sky where you are currently pointing, comparing it to a star map, and figuring out exactly where you are pointing. Now there are nuances to the process which make it not completely simple. However, there are many software vendors who have incorporated the magic of plate solving into easy to use, and accessible software.
Why Does It Matter?
Have you ever tried to find a target in the night sky and just can’t do it? Does your star finder tell you that you are pointed in the right spot, yet, there is nothing there? Does your telescope mount synchronization program tell you to center a particular star and press enter? (Easier said than done.) I see a bunch of stars. Is that the right one or is it this one? Maybe it’s none of the ones I see.
If you have these frustrations, then plate solving is for you. I will discuss Plate Solving in the context of using Astrophotography Tool (APT). Astrophotography Tool is a session manager program that provides an interface for all your equipment to work together. It is a one-stop-shop for pointing your telescope, operating your tracking mount, setting your imaging plan, operating your camera, and, of course, plate solving. APT is just one of several session mangers. Some use N.I.N.A, Sequence Generator Pro, and a number of others. All of these do roughly the same thing.
There are many plate solving programs that will interface with these session managers. I use All Sky Plate Solver (ASPS), Plate Solve 2 (PS2), and ASTAP. ASPS is a blind plate solver. This means that you don’t need to know anything about where you are pointing. The program will still figure it out. This program normally takes about 30 seconds to tell you where you are pointed. If you use ASTAP or PS2, it usually takes one or two seconds, however, you need to tell the program the general part of the sky where you are pointing. You can do this by selecting a star, or a celestial object as a reference point for the program. This is not a problem though since you only need to get within about 180 degrees.
APT will plate solve the image and then send a visual location to Stellarium (online observatory). This is extremely helpful when you are pointing manually using a narrow field of view. N.I.N.A. does not do this. I don’t know about the others.
When I first started astrophotography, I dismissed plate solving as an advanced feature I would learn later after I I got the basics. BIG MISTAKE. Plate solving is not a complicated process for advanced users. It is made simple by the software we use and is a great benefit for novice users. Stop wasting valuable imaging time looking for your target. Use plate solving and go immediately to your target.