Selztal Observation Site

3I/ATLAS - The interstellar visitor

Currently 3I/ATLAS passes as comet our solar system. It is the third object we can observe that enters our system from outside, traveling through insterallar space originated from a distant star.
The first interstellar visitor we were able to detect was in the year 2017 1I/'Oumuamua followed by comet, 2I/Borisov  in 2019.
3I/ATLAS will follow a track with a perihelion between Earth and Mars orbit passing October 29th and closest distance to earth about December 19th at a distance of 1.8 AU. This significant distance is the reason for 3I/ATLAS not being bright enough to allow a visual observation by using telescopes available to regular amatuers. It will remain an object which can be tracked by photografic observations only. The expected brightness is uncertain and in the range of 16 to 14 magnitudines.

At July 29th, 2025 I got the chance to hunt for this target using the VDS Remote Telesope located in Namibia / Hokos. Estimated current brightness is about 17.4 +/- 0.1 mag. 

Left: show in the movement of 3I/ATLAS durch time of 6 exposures 120s each. Right: images stacked on  3I/ATLAS centered.
The slighlty elongated appearance is not the true shape of the object because during the single exposure the comet moves about 3 pixel. So short exposures, or tracking directly on the coment has to be performed next time.