SUNSET: 
0
Photographer:
cwmauche
Location of Photo:
Santa Fe, NM
Date/Time of photo:
2025 August 4, 4:22-5:46 UT
Equipment:
Celestron 925 EdgeHD telescope, 0.7x Reducer, Optolong UV/IR filter, ZWO ASI2600MC Pro camera
Description:
Between 2025 August 4, 4:22-5:46 UT, despite the ~first-quarter Moon being nearby, I took 40 2-min exposures of the sky at the predicted position of 3I/Atlas (C/2025 N1). The comet isn't visible in the individual sub-exposures or -- having moved 146" during the sequence -- in the star-stacked image, but it shows up faintly after applying the offsets needed to stack on the comet. Because the comet passed very close to a star (Gaia DR3 4133483401917026816) during the sequence, I dropped 10 subs from the middle of the sequence to better isolate the comet on the sky. The image is a cropped binned composite of the star-stacked and comet-stacked images. The limiting magnitude of the star-stacked image is 19.4. The comet is circled and labeled in the insert.
