• 8th March 2024 - Friends Event

    Spring Sky - Observatory @8pm

    The Dome will be open for Friends to observe the Spring Sky and its plethora of galaxies.
    This event is weather dependent, check for updates nearer the time.

  • 21st March 2024 - Friends Event

    NASA/ESA Sun-Earth Day Lecture - Garnett Room @7.45pm

    This year's NASA/ESA Sun-Earth Day Lecture will be given by Professor David Southwood on the topic "Space Weather: Electromagnetic Threats from the Sun"


Marlborough College

Welcome to the Marlborough College Blackett Observatory, home to the largest refracting telescope in Wiltshire. The Observatory is a key facility for the study of Astronomy by pupils at Marlborough College. It is open to the public through the Friends of the Marlborough Telescope membership scheme. School and Society visits are welcome, please contact the Director to arrange your visit.

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What's Up!

Week of 19th February 2024

  • Astronomical twilight ends at 19:20 UT at the start of the week and at 19:30 UT by the end of the week.
  • Jupiter (-2.3) sets at around 23:45 UT this week, sinking ever further to the west as this apparition draws to a close.
  • As the Moon waxes to Full, spend some time exploring the areas of Mare Imbrium with the Jura Mountains and Oceanus Procellarum with craters Copernicus, Kepler and Aristarchus.
  • The Moon is Full on Saturday – the Snow Moon.
  • The Sun currently has 7 active regions and the sunspot number is 100.
  • There are no visible evening ISS passes this week.
    (For full details about ISS passes click this link: heavens-above-iss-passes to visit the heavens-above website. If you are not in Marlborough, please ensure that you set your location for the most accurate ISS timings).


Visit the What’s Up! archive

Latest News

What's been going on at the Blackett Observatory

20th February

Outreach Visit: The first group of Cherhill Cubs (19 Cubs and 3 Leaders) visited the Observatory with GKWJ. It was cloudy. The group enjoyed a virtual Sky Tour in Stellarium, a visit to the Dome and a series of photographs of the Moon.

19th February

Outreach Visit: The final group from Cothill House prep school, consisting of 11 pupils and two staff, visited the Dome with GKWJ on a hazy evening. We tried to observe the Moon through the 10-inch, but the cloud was too thick. The group asked a whole range of great questions, looked at a selection of images and enjoyed the Campo Del Cielo meteorite from the Wetton Collection.

18th February

Friends Observing: 14 Friends joined GKWJ and JAG at the Observatory for this year’s Lunar Observing event. Conditions were far from perfect, with fast moving cloud, but there were sufficient breaks for observing to take place. We started at 90x magnification and a glorious view of the 68% Waxing Gibbous Moon. Up to 140x for closer views of the Sea of Showers with the Apennine mountain range at its edge, including the tallest mountain on the Moon, Mount Huygens at 6000 metres, then to crater Clavius in the south. Mag up to 220x to spot Rupes Recta, the ‘Straight Wall’ cliff face in the Sea of Clouds, and a view of the Apollo 11 landing site in the Sea of Tranquility. The cloud had thickened too much at this point, so the group took a seat in the warm room where a Friend shared some key pieces from his Moon Memorabilia collection with us, including a mission patch worn by Neil Armstrong, the Retro Timer Unit and a ‘Remove before Flight’ tag that still smells of kerosene!

14th to 17th February

Friends Outing: An intrepid group of 17 Friends headed out to Kilpisjärvi, Finland at 69°N in search of the Aurora Borealis. Armed with thermals to survive the -15°C arctic conditions, the group enjoyed a snowmobile safari to the 3 borders point where Finland, Sweden and Norway converge, a Sami reindeer experience learning about the culture and ways of Lapland, and a night time snowmobile safari. Some of the group went on excursions for ice fishing on the lake and snow shoe trekking across the tundra. The absolute highlight of the trip was on the Thursday evening when the sky was perfectly clear following a beautiful sunny day, the group went down to the frozen lake to view the night sky. After about 45 minutes, a strange grey-ish cloud arced over the northern horizon. It soon turned a greenish colour and a stunning display of the Aurora started. The shimmering green curtains of light came in waves, dancing across the sky. The display lasted for about an hour, making the trip a complete success.



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All Sky Eye

The Latest View from the MCBO

The All Sky Camera operates from 30 minutes after sunset through the night until 30 minutes before sunrise. The latest image is updated automatically every 5 minutes and the time lapse video is refreshed each morning at around sunrise. Click the still image to view a large version


Latest Still Image

Most recent time lapse video

Sky Quality

The Latest SQM Chart from the MCBO

Thanks to generous funding from the North Wessex Downs National Landscape, the Blackett Observatory now has a fixed Sky Quality Meter (SQM) in place, measuring sky darkness every night throughout the year.


This is the latest chart of SQM readings, measured in magnitudes per square arcsecond (mpsas). The darkest reading to date is 20.8 mpsas, which equates to Bortle 4.5 and a naked eye limiting magnitude of +6.0. The sky will now be monitored constantly to see how the effect of light pollution is changing over time. A project to monitor sky quality across our local area is underway using NWD funded handheld SQM devices and volunteers from the Friends of the Marlborough Telescope.

The SQM chart updates every 15 minutes through the hours of darkness.
The yellow circles show the altitude of the Moon, if present.