Comet C/2021 A1 (Leonard)

After many nights planning my attempt to capture Comet Leonard, I ended up with two sets of images that turned out really bad - comet head at edge of image frame in both cases. Turns out that Stellarium, my planetarium and telescope pointing application, doesn't precisely calculate comet positions. So, I decided to set up Horizons (part of Astro-Physics APCC-Pro software) to use JPL coordinates in realtime to track the comet. I created a sequence in NINA software to turn on my equipment, slew to the comet and take 20x60sec subs in each filter, R, G and B. Since the image run would start at 5:00AM, I went to bed - the scope was on full automatic. The next morning I checked the images and was pleased to find I got all the images with the comet centered in the frames. Success! But, later, when I started to process the images I found out that there was a problem.

Although the mount tracked on the comet fairly well, it wasn't good enough - there was some drifting in DEC. The result made it impossible to properly register the images as the stars trailed a little on each exposure (as expected) but so did the comet. I was then forced to manually register the frames. With elongated stars I was not able to process an RGB stars only image so I had to settle for the star trails. 

To make matters worse the position of the comet (in the east, south-east) placed it right over Baltimore's light dome, at a fairly low altitude. I didn't have the LP filter installed (I forgot) and so had to process out as much of the skyglow as I could and still get a decent image. But here it is. With the comet dropping lower in the east I doubt I'll have another attempt to capture it in the future.

Comet C/2021 A1 (Leonard)
GT102 f/5.6
ASI2600mm 18x60sec R, 18x60sec G, 20x60sec B

I plan to spend some time experimenting with Horizons to determine why I was getting drift in the comet's position as this software was designed to make these type of image runs. More on this in a future blog.