Venus Occultation 2026: A Sky Phenomenon with Many Faces Across Different Regions
People in several parts of western Indonesia witnessed a rare celestial phenomenon on Monday (14/9): the occultation of Venus by the Moon. During the event, Venus slowly disappeared behind the crescent Moon’s disc before reappearing some moments later.
The phenomenon was also observed through the Venus Occultation Observation Livestream hosted by the Bosscha Observatory of the Bandung Institute of Technology (ITB) from 7pm to 9pm Western Indonesia Time. The live broadcast combined observations from the Bosscha Observatory with a number of collaborators across Indonesia and abroad, including Lampung, Bengkulu, Banten, Semarang, Lamongan, Yogyakarta, Medan, Padang and Bangkok.
An occultation occurs when the Moon, moving along its orbit, passes directly between the Earth and Venus from the observer’s point of view. As a result, the lunar disc temporarily blocks the light of Venus as seen from Earth. The differences in appearance across regions formed one of the most fascinating aspects of the observation.
The ITERA Lampung Astronomical Observatory (OAIL ITERA) was located within the occultation zone. During the live stream, Venus appeared as a bright point of light near the crescent Moon before gradually approaching the lunar edge and disappearing behind its disc.
Observations from the Bosscha Observatory in Lembang, West Java, also showed Venus drawing closer to the Moon. Comparing the two locations revealed that the apparent position of Venus relative to the Moon can differ depending on where it is observed from. This difference arises because the Moon is far closer to Earth than Venus, so a shift in the observer’s position on the Earth’s surface produces a different viewing angle on the relative positions of the two celestial bodies.
“The Moon is closer to Earth than Venus, which is why the apparent positions of the two bodies can differ when observed from different locations,” explained Agus T. P. Jatmiko, a researcher at the Bosscha Observatory, during the Venus Occultation Observation Livestream.
According to Agus, the difference was clearly visible in reports from several locations. Yogyakarta, for example, lay outside the occultation path, so the Moon and Venus appeared only close together in a conjunction. Meanwhile, observations from Semarang showed near-grazing conditions, where the apparent track of Venus passed very close to the Moon’s edge. In general, the occultation proceeded gradually. From within the occultation path, Venus appeared to approach the Moon’s edge, then disappeared behind the disc for some time.
“After that, Venus re-emerged from the other side of the Moon. Differences in location mean the time of disappearance, the duration of cover and Venus’s position on re-emergence can all vary,” he explained.
Beyond geography, weather conditions played a crucial role in the success of the observations. In Bangkok, Robin of WRWO Space reported cloudy conditions; the Moon was visible for about a minute before being obscured by cloud again. In Medan, the OIF UMSU team also faced rain and drizzle, making it difficult to observe the Moon and Venus properly.
Similar conditions occurred in Padang. Bima of the West Sumatra astronomy community reported thick fog at the observation site, located at an altitude of about 1,200 metres above sea level, even though the team had prepared a smart telescope for the occasion.
“The most important things in observation are that the instruments are ready, the observers are ready, and finally the weather is good,” said Agus.
Observations from Lamongan further showed how atmospheric conditions and instruments can affect results. The Moon appeared reddish because it sat low near the horizon, while Venus did not fall within the instrument’s field of view. Based on the occultation path map shown during the live stream, Lamongan lay outside the zone of full occultation.
Through simultaneous observations from multiple points, the Bosscha Observatory demonstrated that the outcome of an astronomical observation is determined not only by the event unfolding in the sky. The observer’s location, the positions of the celestial bodies, the timing, atmospheric conditions and the instruments used all help determine what can be witnessed from any given place.
The collaboration also allowed the public to directly compare how a single astronomical event can appear differently. In one region, Venus vanished behind the Moon; in another, the two merely appeared close together; while elsewhere the phenomenon was barely observable at all, obscured by cloud, rain or fog.
The Venus occultation of 14 September 2026 was thus not merely an exciting sky event to watch, but also a lesson in celestial geometry and the importance of observing from multiple locations to understand a single astronomical event more completely.