03.09.2021 – Moon occulted Kappa Gem

Observation report

On the evening of September 2nd, 2021 I discovered by chance that in the morning of September 3rd, 2021 the moon will cover the star Kappa Gem. Unfortunately, after missing some star occultations earlier this year or when the weather just wasn’t good, the sky should be guaranteed to be cloudless this time. At the time of occultation, the moon would only be illuminated to about 15% and the star Kappa Gem is at least +3.5 magnitude bright. The moon had not covered such a bright star so far in the year. Due to the guaranteed good weather, I didn’t mind getting up early. The star will disappear behind the moon around 4:40 a.m. and reappear an hour later, around 5:30 a.m.

My alarm clock rang punctually on September 3rd, 2021 at shortly after 4 a.m. and it was time to set up the telescope and its accessories. Of course, due to the numerous observations, I already had routine in it and that was done in a few minutes. I took a first photo at 4:24 a.m., but without a telescope. Kapp Gem could still be seen clearly to the left below the moon with the Canon 500D. But it was nice to take pictures of the moon with the earth’s shadow and the surrounding stars. Then around 4:30 a.m. it was time to really point the telescope and camera towards the moon. In that moment the star was still in a bit distance the moon, but I could take already some great pictures. Overexposure made it possible to see the not illuminated part of the moon with its ash-gray light. Since Kappa Gem is a comparatively bright star, the exposure could also be reduced so that the details of the moon were clearly visible, but at the same time the star was also still recognizable in the photo. This is often not the case with weaker stars.

Around 4:40 a.m., Kappa Gem got closer and closer until I got the very last pictures at 4:45 a.m. before the star visually disappeared behind the moon. In that moment I took some more pictures to document the beginning of the eclipse of the star (see photos below the post). While the star was then behind the moon, I used the clear sky to take a few pictures of the constellations, but of course also to take pictures of the crescent moon. From 5:35 a.m. I made my first attempts to catch the star directly as soon as it emerged from behind the unlit part of the moon. At 5:40 a.m. the time had finally come, and Kappa Gem reappeared. Here I also used the opportunity for a few overexposed photos to take the entire moon including the unlit part with the star. Until 5:50 a.m. I took pictures again without a telescope to get some pictures of the moon and Kappa Gem with the surrounding stars. The twilight also slowly showed itself in the photos with a beautiful dark blue sky.

For me this occultation of Kappa Gem by the moon was one of the most beautiful star occultations and I was very happy that I had got up early for it. Especially after a long time, it was great to watch such an event again. Below you will of course also find a few photos that I was able to take during the observation: