TLE can be observed in a time interval of 2.5 years. The last total lunar eclipse to occur in Indonesia is in 2018. The level of darkness of an eclipse was determined using the Danjon scale with a value range of 0 to 4. A very dark eclipse had a Danjon scale of 0.

When TLE occurs, the red color that appears is caused by sunlight scattered by dust and molecules in the Earth's atmosphere. The blue color is scattered more strongly while the red color can pass through the Earth's atmosphere and reach the moon's surface. The darkness of this lunar eclipse can provide some important information.

"Later, when a lunar eclipse occurs, assuming the weather permits, the moon will darken. So the normally white full moon will turn dark. Well, the darkness will depend on atmospheric conditions," said Agus Triono, Bosscha Astronomer. He also added that the level of pollutants in the atmosphere also determines the level of darkness of the full moon.

The moon's color at the observation during TLE depends on several factors: the amount of moisture content, the rate of air pollutants from combustion, the occurrence of factory smoke, motor vehicle fumes, and dust or ash content of volcanic eruptions. The more material it contains in the atmosphere, the darker the moon's color.

Regarding this rare phenomenon, Bosscha Observatory held a virtual observation of the night sky (VONS) during the total lunar eclipse on May 26, 2021, in collaboration with the University of Nusa Cendana in Kupang, East Nusa Tenggara, the community of astronomy lovers of Eastern Sky Lovers (Pelati), and an amateur astronomer from Kupang, Zulkarnain.

Total lunar eclipse observations would be conducted in Bandung and Kupang. Observing a lunar eclipse in Kupang is easier to do. The probability of the moon's visibility is higher because the moon is higher and the weather is brighter than in Bandung.

VONS's broadcast could be watched through Bosscha observatory and Slido YouTube channels on Wednesday starting at 17.00 WIB. By joining Slido, people could participate in interactive discussion sessions by asking and answering questions, also participating in polls. To be able to join Slido, the public could register for free via https://bosscha.itb.ac.id/id/jasa/pvlm/ starting on Tuesday (25/05/2021) at 19.00 WIB. It was limited to only 700 people.

Reporter: Restu Lestari Wulan Utami (Biology, 2017)
Translator: Zahra Annisa Fitri (Urban and Regional Planning, 2019)