A report an photos by Dr. Thomas Kunzemann
All planets and also the moon move on orbits close to the ecliptic [1]. Since the lunar orbital plane is slightly inclined against that of the planets, individual planets can be occulted by the moon from time to time. Such a cover was predicted for September 19, 2025. The observation of such an event is an astronomical highlight, because you can experience celestial mechanics live.
However, the observation should not be easy, as the occultation took place around 13h00 CET, i.e. in daylight. Three days before the new moon, the narrow crescent moon was only about 5% illuminated and could only be found in the telescope. At the time of occultation, Venus was 1.45 astronomical units, i.e. about 217.5 million km from Earth, had an angular diameter of 11.5 arc seconds and was significantly brighter than the Moon at -3.9 mag. At that time, the Moon and Venus were only 30 arc minutes northwest of the star Regulus in Leo. The event was supposed to take place just 26° west of the sun. Therefore, extreme caution was advised, because an unprotected view of the sun through the telescope can lead to blindness.
On the 19th, around noon, the sky was clear except for a few cirrus clouds, and my observation balcony offered a clear view of the event.
The moon slowly moves towards Venus and then moves closer and closer...…
The "hot phase" begins – shortly before the complete occultation
Observation was carried out with a refractor, Vixen NA 140 on GPDX mount, and Skysensor 2000 control. A Canon R, which was mounted with a folding mirror in the focus of the telescope, served as the recording camera. The second output of the folding mirror was equipped with a 40mm homofocal eyepiece to follow the event visually. The approach of the Moon to Venus was recorded at intervals of 5 minutes, and just before occultation, the interval was shortened to one minute. In between, thin cirrus clouds moved through the picture. The images were contrast-enhanced with Adobe Photoshop. Unfortunately, denser clouds moved in after the occultation occurred, so that the exit could no longer be observed.
Interesting links:
[1] Ecliptic: https://en.wikipedia.org/wiki/Ecliptic
