• 14th October 2023 - Friends Event

    Observing the Autumn Sky - Observatory @ 8.30pm

    Explore the Autumn Sky by naked eye, through binoculars and with the 10-inch telescope at this Friends observing event. If it is cloudy, there will be a short presentation and a Q&A session. See you there!


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.

FIND OUT MORE      Become a Friend      CONTACT

What's Up!

Week of 25th September 2023

  • Astronomical twilight ends at 20:52 BST at the start of the week and at 20:37 BST by the end of the week.
  • Saturn (mag +0.5) lies at an altitude of about 15° in the southeast with Jupiter (-2.8) in the east, rising at around 20:10 BST, reaching a maximum altitude of 53° as it transits at around 03:45 BST.
  • Neptune (+7.8) lies 25° east of Saturn and Uranus (+5.7) is 8° east of Jupiter.
  • The Moon is Full on Friday – the Harvest Supermoon
  • The Sun currently has 12 active regions and the sunspot number is 198.
  • There are multiple 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

25th September

Outreach Visit: 12 members of the Bath Astronomers visited the Dome on a partly cloudy evening. GKWJ and JAG first slewed the 10-inch to the waxing gibbous Moon, which was visible through the cloud. Small clear patches allowed Albireo to be viewed next; easily split and with a glorious colour difference between the two stars as ever. Unfortunately, observing was cut short by thickening cloud. The group enjoyed a selection of images taken at the Observatory, watched the radio meteor detector live feed, where multiple events were seen, and marvelled at the Wetton Meteorite Collection.

22nd September

Friends 19th Drinks Party: GKWJ hosted the 19th Anniversary Friends Drinks Party at the Observatory. A total of 57 Friends and family were present to help consume the vast array of canapés and drinks. Many new Friends attended, along with longer standing Friends, some of whom had even attended the inaugural party! A lull in the recent poor weather allowed the party to be held on the observing platform, with the First Quarter Moon visible through breaks in the cloud. As darkness descended, the stragglers were treated to a clearing sky. GKWJ and JAG gave a sky tour of the main constellations; multiple satellites and an excellent overhead ISS pass were also seen. One Friend set up binoculars, through which Saturn and Neptune were observed. It was a wonderful start to the 2023/24 Friends observing year.

15th September

SQM Start: GKWJ set up the fixed SQM on the outside of the classroom and configured the software for continuous nighttime data gathering. The first data set of a full night of magnitudes per square arcsecond (mpsas) readings taken every fifteen minutes was gathered, with the highest reading being 20.78 mpsas. We can now empirically monitor the sky quality at the Blackett Observatory. A project to monitor sky quality across the local area will commence this autumn.

14th September

Sky Quality testing: The new Sky Quality Metering project commenced with a kit testing session at the Observatory by GKWJ & JAG. The fixed Sky Quality Meter (SQM) system was successfully connected up and tested in various locations on the exterior of the classroom; a decision was taken for its permanent location.

4th September

Planetary Imaging: Another planetary imaging session through the 10-inch by GKWJ and JAG. Saturn was captured, this time with five moons, including a first capture of Enceladus. Jupiter was attempted, but its low altitude at that hour led to awful data and an unsuccessful image.



Visit the News archive

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