Finding Pluto
December 2022 :
Over the past few decades, there has been a lot of talk about Pluto from losing its status as an official planet to the spectacular fly-by images of the New Horizons spacecraft. It's an object that was so remote and dim that I never thought of actually seeking it out. Looking at my planetarium program, I soon discovered that Pluto’s magnitude was 14.4. I wasn’t quite sure what the limiting visual magnitude on my 152mm f5.9 refractor was but after finding an online calculator for that question, I got my answer, 12.5. I did find the math for calculating limiting magnitude an interesting topic that I may expand upon in a future article. The bottom line was, I wasn’t going to see Pluto visually through my telescope.
All summer long I had my telescope configured for deep sky imaging and it dawned on me that Pluto was more of a stellar object. My deep sky camera would give me the image I wanted. I knew that my mount would center on the target but would I be able to pick out Pluto, and how would I identify it from all those other points of light?
I took a 15-second image, plate solved, and adjusted the mount for the slight pointing error. I then took a 3-minute image. The picture came out great but which point of light was Pluto?
Using my planetarium program I knew the exact celestial coordinates for Pluto at that time. To make sure, I did a plate solve on the 3-minute image and then used an astrometric tool to click on the point which I thought was Pluto. One click on the object and the exact coordinates I was looking for were displayed. I had identified Pluto!
It may be a trivial exercise but it brought me great satisfaction to stick with it and get a positive id on this now dwarf planet.
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