Clouds arrived late afternoon on Friday, 12 December 2025. Made for a nice sunset.

The sky was clear early Tuesday morning, 16 December, so I opened the observatory to observe and image an interstellar visitor, Comet 3I/ATLAS.

Open: Tuesday, 16 December 2025, 0200 MST Temperature: 54°F

Session: 2110 Conditions: Clear

Equipment:
12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
2" 30mm UWA eyepiece

Camera:
iPhone 15 Pro Max
D850 DSLR

Upon arrival at the observatory I took a Sky Quality reading.

0207 MST: LX600 ON, StarLock OFF, High Precision OFF.

SYNCed the AutoStar on the star Regulus in the constellation of Leo. The comet was near Regulus.

0211 MST: Wi-Fi ON.

Used SkySafari 7 Pro on the iPhone 15 Pro Max to GOTO Comet 3I/ATLAS. This visitor to our solar system from interstellar space was easily seen in the eyepiece, 102X. A small coma was visible, but no tail.

Began preparing the cameras for imaging.

0228 MST: A friend from Oracle arrived to observe Comet 3I/ATLAS. He observed the comet, 81X.

Attached the LiDAR Cover on the iPhone and mounted the phone on the 2" 30mm eyepiece.

0237 MST: StarLock ON.

Took this StarLock autoguided afocal 81X image of Comet 3I/ATLAS using the iPhone 15 Pro Max Camera app (Night Mode, 30 seconds, 1X lens).

Mounted the D850 DSLR at prime focus, focused on Regulus, and locked the 12" primary mirror. Using SkySafari 7 Pro on the iPhone, slewed the telescope back to the comet. Did some framing test images and then took this StarLock autoguided image (1 minute, ISO 5000). A satellite (or two) is also visible in the image.

This 5 minute exposure shows the rapid motion of the comet as the comet nucleus is trailed.

0338 MST: StarLock OFF, Wi-Fi OFF.

We viewed Comet 3I/ATLAS, 102X. As interstellar visitors to our solar system are rare, it was exciting to see it with our eye.

0353 MST: LX600 OFF.

Close: Tuesday, 16 December 2025, 0404 MST Temperature: 52°F

Session Length: 2h 04m Conditions: Clear, SQM 20.84

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See my latest Friends of Oracle State Park Oracle Night Sky Charm article.

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