Context: Recently the 1st official star party for experienced amateur astronomers was organised by the Indian Institute of Astrophysics (IIA) in at Hanle Dark Sky Reserve in eastern Ladakh.

• Spanning from October 12 to October 15, the event attracted around 30 amateur astronomers who traveled to Hanle with their telescopes and cameras to witness the beauty of the pristine dark skies and capture images of celestial objects that are difficult to observe in locations affected by light pollution.

What is a Dark Sky Reserve?

• The International Dark Sky Association (IDSA) defines an international dark sky reserve (IDSR) as “a public or private land of substantial size (at least 700 km², or about 173,000 acres) possessing an exceptional or distinguished quality of starry nights and nocturnal environment, and that is specifically protected for its scientific, natural, educational, cultural heritage, and/or public enjoyment”.

• A dark sky reserve requires a “core” area that has clear sky without any light pollution, which can enable telescopes to see the sky in its natural darkness.

• To support the core, it should be surrounded by a “peripheral” or “buffer” area that supports dark sky values in the core while receiving the same benefits.

How are dark sky reserves identified?

• According to IDSA, it considers land suitable for dark sky sites only if it is on public or private land, is publicly accessible all or part of the year, protected for scientific, natural, educational, cultural, cultural and/or public purposes.

• The central part of the core offers exceptional dark sky resources compared to the communities and cities that surround it, and the core limits the brightness of the night sky to either reserves, parks, or sanctuaries.

• The IDSR also needs to have a comprehensive lighting management plan (LMP) “which should be adopted by a sufficient number of communities within the entire IDSR (core and periphery) corresponding to at least 80 percent of population and 80 percent of designated area of protection”.

• It also needs a description of current and suspected future threats to dark skies over the core zone, and a plan to address these threats.

• This is particularly important as Hanle is particularly close to Chinese territories, which makes it highly sensitive.

• The reserve must also submit a detailed annual report to IDA by October 1 each year.

About Hanle Dark Sky Reserve

• HDSR is India’s first dark sky region which is centred at Hanle in Eastern Ladakh, around the Indian Astronomical Observatory.

• It is India's first Night Sky Sanctuary is located within the Changthang Wildlife Sanctuary.

• The Wildlife Sanctuary is adjacent to the Indian Astronomical Observatory, the second-highest optical telescope in the world.

• The Reserve is promoted as a tourist destination for enjoying the night sky and also helps in socio-economic development of the local villages.

• HDSR aims to control man-made light pollution in the area in order to preserve the pristine dark skies for astronomical research.

• A dark sky is the night sky as nature meant for it to be, without any light pollution.

• This Dark Sky Reserve is among only the 15 or 16 of its kind in the world that will offer a spectacular view of the night sky.

• The Star Party is also likely to evolve into an annual event.

• Bortle scale - The Bortle scale is a 9 level numeric scale that measures the night sky's brightness of a particular location.

• The scale ranges from Class 1, the darkest skies available over the earth, through to Class 9, which denotes the pale, light-marred skies over the insides of cities.

• HDSR region falls under the Bortle Class 1.

How many such reserves exist in the world?

• A dark sky reserve is only one of the designations given by the IDSA, others being international dark sky parks, communities, reserves, sanctuaries, and urban night sky places.

• At present, there are 20 dark sky reserves around the world, seven in the United Kingdom; four in France; two each in the USA and Germany; and one each in New Zealand, Canada, Namibia, and Australia.