Comet Lemmon

Not Very Spectacular

Comet Lemmon was discovered in January 2025 by the Mount Lemmon Survey using a telescope on Mount Lemmon in Arizona. The comet had been featured in astronomical news in October, and I wondered if I could see it. On October 15th, a few days before the comet's closest approach to Earth, clear sky after sunset beckoned me onto my front porch to check the western horizon for signs of the comet. It certainly wasn't visible to the naked eye in my light polluted sky. A tripod mounted Nikon Z6II eventually managed to reveal the modest head and tail.

The first image below is a good approximation of my naked eye view. (You need to enlarge the image to full size by clicking on it to see stars and constellations.) The comet is under the Big Dipper's handle and near the double star, Cor Caroli. These are labeled in the second image below which should also be enlarged to full size.

I set my Nikon zoom lens to 70mm for more magnification and took a 4-second exposure at ISO 3200 and f/2.8. When viewed at full size the next two images reveal the comet near center. The tail is definitely there, but barely visible. Three colorful airplane trails also appear.

The next evening, October 16th, I tried using Seestar to magnify the comet. The next image is a one-minute exposure. It shows the cometary head and coma, but not much tail. Longer exposures revealed a bit more tail but also smeared out the head because the comet moves relative to the stars. The one-minute exposure is disappointing. I need some way to track on the comet head itself instead of stars. That would make longer exposures possible, although stars would then show trails. I wonder if Seestar will someday include a comet tracking option.

On October 20th, one day before the comet's closest approach to Earth, I made one more attempt with the Nikon Z6II. The next image is a 5-second exposure at ISO3200, with lens set at 70mm and f/2.8. I cropped the image to show only the comet. The head and tail are again visible, but not very impressive. 

I'm glad I saw this comet but wondered if my efforts were worthwhile.