By Jett Peters
It seems that once a year, the universe provides astrophotographers with a comet to image, and this year is no exception. Last year, comet C/2023 A3 (Tsuchinshan-ATLAS) passed within 44 million miles of Earth on October 12. It was the major comet event of the year and produced countless eye-catching images of the comet’s green core and billowing gray tail. Many of us at UDRO imaged this target, and some of our images were shared in a previous blog.
This year’s flagship comet is C/2025 A6 (Lemmon), which, I might admit, has a name that is much easier to pronounce. It is currently in the Boötes Constellation and reached its closest approach on October 21st at a distance of roughly 0.59 AU. However, if you have not captured Lemmon yet, there is no need to worry, as the comet will actually continue to become brighter, reaching its peak apparent magnitude at the end of the month. Currently, at the time of writing (October 21st), the comet has an apparent magnitude of 3.9, but estimates suggest by the end of the month it could be as bright as 2.5, making it not only incredibly bright in our images but also rendering it visible to the naked eye.
While the comet was higher in the night sky earlier this month, its magnitude limited viewing and imaging. Right now, the best bet for imaging or viewing the comet is right as the sun goes down. Currently, here at UDRO, the comet starts 20 degrees above the horizon at nautical dusk. This is obviously not ideal for a DSO (Deep-Sky Object) target, but for a comet, especially one of this brightness, only a small amount of data is required.
If you are unsure how to find and track the comet in the night sky for imaging, and you use NINA to control your equipment, the best solution is using the Orbitals plugin. If you are looking to view the comet with the naked eye, an app like Sky Guide for your phone is the best bet.
And, check this great image of comet Lemmon that was the astronomy picture of the day (APOD) for September 30th, 2025.
APOD link: https://apod.nasa.gov/apod/ap250930.html