Project history


The idea of building an observatory specifically as a facility for public outreach and education originated from a group of amateur astronomers with a mutual desire to share their enjoyment and understanding of astronomy.

Several HCO members have professional design and engineering expertise, so the whole group is more closely involved with projects such as the construction of the flagship Millennium telescope.

This section documents the progress of HCO projects and, in particular, the development of the Millennium telescope.


The observatory site at Hanwell is situated on a bank raised above beautiful surrounding woodland. The site already hosted the 12.5-inch McIver Paton reflector when it was surveyed in 1999 for the possible installation of another 14-inch reflector, the unique 30-inch John Wall refractor and the flagship 30-inch Millennium reflector.

As the optical design for the Millennium telescope was finalised, its foundations were laid at the observatory site. A brigade of wheelbarrows transported eight tons of high-spec concrete, donated by Smiths' of Banbury, along with fifteen tons of other materials. A blank of the 30-inch mirror was delivered to the optician in New Mexico in the US, who soon began grinding the glass. (Due to a series of misfortunes, detailed later, this mirror was never shipped.) Meanwhile Andrew Baxter engineered the mirror cell, with 18 floatation points to support the weighty piece of glass, and, with steel-fabrication draughtsman David Peachey, completed detailed construction drawings for the mount and optical tube.

Extensive landscaping work also took place this year as access paths were improved and the bank at the observatory site was levelled into a terrace to accommodate the use of portable telescopes.


In 2000, the mount and tube for the Millennium telescope were fabricated in steel, by local company Riteweld Engineering of Banbury, and assembled in a local barn as a test-run. The two semi-circular rails that would form the turntable were galvanised and bolted to the concrete base at the observatory. Despite being several meters across, tests showed that the rails had been manufactured to millimetre accuracy.

Progress on the 30-inch mirror was patchy this year; a replacement mirror blank was shipped due to problems with the original and, as the new mirror came to completion at the height of summer, fires in New Mexico delayed its delivery to the UK.

Foundations were laid for the John Wall refractor as it was transported from its original home in Dartford, Kent.

In December, the HCO constitution was signed by members present at the annual general meeting.


Over the end of 2000 and the beginning of 2001, design began for drive systems for the Millennium telescope to point it in altitude and azimuth, as well as a dew point detector, to prevent moisture condensing on the mirror, and a solar recharger, to recharge the telescope's batteries. The last major structural component of the Millennium telescope, the integral observing platform constituting one third of the complete steel-work, was generously designed and fabricated free of charge by David Briley and Betgate Structures Ltd.

Assembly of the mount and optical tube came to a halt when the foot-and-mouth crisis denied access to the barn. Progress on the flagship project was further hindered by the news that the mirror had been damaged while awaiting shipping from the US.

Despite difficulties with the Millennium telescope, the recommissioning of the John Wall refractor went ahead with the construction of the mount and pier, another five tons of masonry work.


In 2002, the John Wall telescope underwent the final stages of recommissioning. The secondary mirrors, recently realuminised, were found to be in pristine condition and the optics were soon aligned and collimated. John Wall himself reengineered the drive system. One evening in May, although it appeared that the night sky would be marred by cloud, the Webb Society saw 'First Light' through the fully restored telescope.

A new mirror blank, made of Pilkington glass usually used for radiation shielding, was bought for the Millennium telescope from British Shielding Windows. The 3-inch thick blank was cut to a circle with an ultra-high pressure water jet by AquaCut. An optical test of the glass, conducted by Christopher Taylor, concluded that it was of high quality. In 2003 the blank was delivered to a new optician in London, Terry Pearce, who, having successfully produced a 9-inch mirror from the same glass, began grinding the 30-inch.

Erection of the Millennium telescope at the observatory site began in 2003, once the steel parts had been galvanised by Joseph Ash Galvanisers in Telford, who kindly did this substantial job for no charge. A dummy mirror was made from concrete, ready to test the balance and handling of the telescope with the mirror in place at one end of the optical tube.

Since 2002, HCO has welcomed volunteers from Raleigh International for annual working weekends, improving access to the observatory site and walkways through the surrounding woodland. The working weekends now take place during the Stars and Snowdrops fundraising event, which has been held in February since 2005. This has rapidly become a major fixture region's annual calendar, drawing over 1200 visitors in 2008. Also during each of these years, various public observing events were run by HCO with the existing instrumentation, culminating in our most spectacular exercise in public outreach to date, when some 2000 people saw the transit of Venus through our telescopes in June 2004. See the Events page for more details of this and other previous events.