Follow-up Imaging Observations of the Interstellar Comet 3I/ATLAS
ATel #17664; M. Mugrauer (AIU Jena), M. Belger (AIU Jena), Z. Jamil (AIU Jena), K.-U. Michel (AIU Jena), B. Dincel (AIU Jena)
on 10 Feb 2026; 13:40 UT
Credential Certification: Markus Mugrauer (markus@astro.uni-jena.de)
Between 21 November 2025 and 24 January 2026, we conducted follow-up imaging observations of the 2nd discovered interstellar comet, 3I/ATLAS, using the Schmidt-Teleskop-Kamera (STK). The STK is operated in the Schmidt focus of the 90 cm reflector telescope at the University Observatory Jena. The comet was observed in 14 epochs, and at least ten STK images were taken in the R-band in each epoch with a detector integration time of 120 s. We measured the comet's astrometry and studied its morphology. We also determined the brightness of the coma of 3I/ATLAS using aperture photometry. The comet's orbital elements were determined based on its STK astrometry. During our observation campaign, the R-band brightness of the comet's coma decreased continuously from 12.6 ± 0.1 mag to 15.7 ± 0.1 mag. We derived the absolute brightness of the coma of 3I/ATLAS, assuming pure reflection of sunlight. The average absolute magnitude of the coma was 10.15 ± 0.09 during the first two observation epochs on 21 and 22 November 2025. During the subsequent 12 observation epochs between 13 December 2025 and 24 January 2026, the coma's absolute brightness was 11.15 ± 0.07 mag on average, showing no significant variation throughout this range of time.
Follow-up Imaging Observations of the Interstellar Comet 3I/ATLAS - Online Data
