Discovered at Mount Lemmon Observatory in Arizona in January 2025, Comet Lemmon made a nice appearance in our skies during the fall of 2025. At its brightest, it was about magnitude 3.5 and was fairly easy to see with the unaided eye from a dark location.

The Astronomical Society of New Haven held a few public observing events during the fall, and we were able to provide many of our visitors a good view of Comet Lemmon through a telescope equipped with a wide-field eyepiece. The tail was easy to see through the eyepiece. We told people to take a good look because this comet would not return for more than 1,000 years.

In this picture, taken with an ordinary telephoto lens, the comet has a long tail that stretches for at least 10 degrees against the background stars on the border of the constellations Bootes and Serpens Caput.

Image details: About 10 exposures, each 3 seconds at ISO 12800, taken with a Canon T6i camera and a telephoto lens at 102 mm, f/4.5. 

October 23, 2025