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October Comet Near Corona Borealis

  • Chuck Bueter
  • Oct 4
  • 2 min read

Updated: Oct 8

One of several comets passing through the inner solar system in October 2025 will be in the starfield containing the constellation Corona Borealis (CrB). So if you are regularly imaging CrB in hopes of catching an anticipated nova there, as I am, you may capture a bonus comet in the field of view.


Opening October, Comet C/2025 A6 Lemmon is under the Big Dipper in the morning sky, but transitions mid-month to an evening target. After October 20, its closest point of approach to earth, Comet Lemmon is moving daily from right to left through Bootes, whose bright star Izar is one of the key stars for finding the site of the recurring nova in CrB.


As an added bonus, the night of October 20-21 is the peak of the Orionid meteor shower, remnants from Halley's Comet. That night is a trifecta of highlights.


From the handle of the Big Dipper, follow the arc to Arcturus.  Above it in the second half of October will be Comet Lemmon, in the same field of view as Corona Borealis.  Image: 2025 Oct. 3 from New Buffalo, MI.
From the handle of the Big Dipper, follow the arc to Arcturus. Above it in the second half of October will be Comet Lemmon, in the same field of view as Corona Borealis. Image: 2025 Oct. 3 from New Buffalo, MI.

Comet Lemmon will be low in the twilight and setting further, so a clear western horizon is needed. You're playing a timing game of it being dark enough before the comet is too low in the horizon haze. Some astronomers suggest Comet Lemmon may become naked-eye visible from dark skies. However, a long duration exposure with a cell phone in night mode will likely pick up the comet.


In an image from October 5, 2025, taken with a cell phone before sunrise, the comet appears without a tail near the Tania pair of stars.


Comet C/2025 A6 Lemmon, in red circle, appears without a tail in a 10-second exposure taken with a cell phone on October 5, 2025.
Comet C/2025 A6 Lemmon, in red circle, appears without a tail in a 10-second exposure taken with a cell phone on October 5, 2025.

One year ago, Comet Tsuchinshan-ATLAS similarly passed through the starfield containing Corona Borealis.

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