Birla Industrial & Technological Museum (BITM), Kolkata, opened its much-awaited Astro Nights today, December 5, with an evening dedicated to witnessing one of the year’s most striking celestial events - the final Supermoon of 2025. As the moon rises fully illuminated opposite the sun, glowing high above the eastern horizon, sky-watchers are set to witness the breathtaking beauty of the December “Cold Moon” or “Long Night Moon,” traditionally linked with winter’s deepening chill and lengthening nights.
Tonight’s full moon appears especially dazzling as it passes within 90% of its perigee, the closest point to Earth in its 27-day orbit. This rare positioning gives rise to a remarkable supermoon, which can appear up to 14% larger and 30% brighter than the smallest full moon of the year. As it ascends near the horizon, observers may also notice a warm yellow-orange glow - a result of Rayleigh scattering, where Earth’s atmosphere filters out bluer wavelengths of light. Adding to the awe, the well-known “moon illusion” may trick viewers into perceiving the lunar disk as larger than it actually is when it sits low against earthly landmarks.
This month’s full moon will also travel higher across the night sky compared to previous months, compensating for the sun’s shallow winter path as the northern hemisphere approaches the winter solstice on December 21.
To help the public witness these celestial wonders up close, BITM has organised a special Telescope Observation session from 5 PM to 7 PM today and tomorrow (December 5 and 6). Visitors will be able to view prominent lunar features - including vast lunar maria, ancient basaltic plains, and large craters and mountain ranges - which become particularly vivid through telescopic lenses.
Ahead of the main sky-watching event, BITM is also hosting an engaging lineup of moon-themed programmes. These include a Science Show, a hands-on DIY Workshop, and an Open-House Quiz, offering an exciting blend of learning and entertainment for participants of all ages.
Entry to all activities is free after 5.30 PM at the museum premises, making Astro Nights an accessible and enriching experience for families, astronomy enthusiasts, and curious learners eager to celebrate the magic of the December supermoon.