• 26th February - Friends Observing

    Lunar Evening - Observatory @ 8pm

    This evening will be dedicated to observing the Moon.
    If clear we will look at the Moon, if cloudy we will talk about the Moon...


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 6th February 2023

  • Astronomical twilight ends at 18:59 GMT at the beginning of the week and at 19:09 GMT by the end of the week.
  • Comet C/2022 E3 (ZTF) has passed perigee and is now heading away from Earth. It is decreasing in brightness, currently about mag +5.7. You will find the comet passing through Auriga into Taurus this week. The bright moonlight will hinder the view, so it will be easier to see later in the week, in the relative darkness before the Moon rises.
  • Mars (-0.1) is high in our evening sky, though steadily decreasing in apparent size. Jupiter (-2.2) is sinking ever closer to the western horizon, setting at around 21:30 UT this week. Venus (-3.9) is the ‘evening star’ appearing close to the southwestern horizon around sunset.
  • The Moon is Waning Gibbous all week.
  • The Sun currently has four active regions and the sunspot number is 66.
  • There are no visible evening ISS passes this week.


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Latest News

What's been going on at the Blackett Observatory

6th February

Radcliffe Society: A rare alignment occurred for this term’s fixed meeting of the Radcliffe Society – a clear sky and a comet near the Zenith! 11 members of the Society joined GKWJ and JAG at the Observatory, where they observed Comet C/2022 E3 (ZTF), first through binoculars, it was not visible by naked eye as a 99% Waning Gibbous Moon drowned out the fainter objects and the comet was about mag +5.8. Two other members of staff also visited to view the comet. It was then observed in an ETX, the 4-inch refractor and the 10-inch. Everyone made a sketch of the comet relative to the background stars through the 10-inch, noting the time of their sketch. Then a second sketch was made around 20 minutes later. This allowed calculations to be made to estimate the comet’s speed across our line of sight. Values of between 35 km/s and 65 km/s were obtained. The ‘official’ value is around 50 km/s.

31st January

Pupil Observing: GKWJ made the Dome available to members of Radcliffe Society and the GCSE Astronomers for the evening, allowing them to observe Comet C/2022 E3 (ZTF). 20 pupils from across the year groups came to observe. They all saw the comet in the 10-inch, watching the fuzzy patch move across the field of view, with noticeable change in even just a few minutes. The comet was also viewed in binoculars outside and the Moon was observed through an ETX.

Shell Visit: The final Shell visit enjoyed clear skies as the 12 boys from Turner joined GKWJ at the Dome along with their HM. There was a bright, 75% Waxing Gibbous Moon. They were given a tour around the main constellations, also spotting Jupiter, Mars and the Pleiades (M45). They observed a faint fuzzy patch above and to the east of Polaris in binoculars, Comet C/2022 E3 (ZTF). The group moved to the 10-inch to observe the Moon, where the Apennine Mountains were looking particularly impressive close to the Terminator. Unfortunately, before being able to move to the Comet, it clouded over, so the session ended with a discussion about asteroid and comet impacts on Earth.

30th January

Pupil Observing: Broken cloud allowed a varied evening of observing for two pupils with GKWJ and JAG. A Hundred pupil continued their Aided project, making observations of Algol in its dimmed state. Photographs of Star Trails were taken. Comet C/2022 E3 (ZTF) was first seen by averted naked eye as a very faint fuzzy patch close to Polaris. Binoculars revealed an obvious nebulous region. In the 10-inch, the coma was very clear, along with a suggestion of the dust tail. Sketches were made at roughly twenty minute intervals, showing significant movement. Much to the group’s amazement, the comet could be seen to move before our very eyes relative to the background stars over a period of about one minute. Towards the end of the session, a member of Staff and two family members joined the group to observe the comet.

28th January

Public Open Evening: The Observatory was opened to the public with two ticketed sessions seeing 37 people visiting in total. The public interest in astronomy is evidently high as the limited tickets sold out within 25 minutes of being made available some 10 days before the event. The evening was cloudy, so GKWJ and JAG spoke about the history and current use of the Observatory and showed a selection of photographs taken through the Cooke 10-inch and around the Observatory. The sessions ended with a look at the radio meteor detector live stream (though it was very quiet and only a handful of events were seen) and the Campo del Cielo Wetton meteorite.

27th January

Outreach Lecture: GKWJ delivered a lecture with Friend, Nick Howes, to a large audience of over 160 people in the Town Hall on the topic “How to enjoy the night sky” as part of the continuing Marlborough Dark Skies offering. Before the talk started, clear skies enabled a 4-inch refractor to be set up on the balcony of the Town Hall and many attendees observed the First Quarter Moon and Jupiter with its four Galilean moons. Many excellent questions were asked and all under 16s, which accounted for about half the audience, were given a small meteorite to take away.



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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


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