Tuesday, 27 March 2018

SWHAS 50th Anniversary

History of the Society

Former Chairman Graham Marett gave a very interesting talk on 23rd March describing some key events in the history of the South-west Herts Astronomical Society (SWHAS). The society was founded after a chance encounter in the Watford camera shop with the first meeting held on 23rd February 1968. The first chairman was Jan Willemsteyn. In 1970 the meeting venue moved to the Royal Masonic School where meetings still take place today.

The observatory at Flaunden (named "High Top" by Jan) was established in 1974 with a small plot of land leased from a local farmer. Colin Reeve led construction of the dome which was equipped with a 3.5-inch Cooke refractor. In 1982 the Octagon building was constructed to house the Cooke instrument while a 10-inch reflector was installed in the main observatory. In 1998 Allan Swan began construction of a larger 14-inch reflector which was in regular service until 2015, when it was replaced with a Celestron C11 Schmidt-Cassegrain on a modern computerised EQ8 mount.

Stargazing event

The Society hosted a Stargazing event on 24th March at the recently reopened Hub in Cassiobury park. Needless to say the weather was cloudy with rain showers but there were plenty of space-themed activities indoors. As well as the exhibition (on display until 7th April) we were lucky to have Apollo rock samples, meteorites, a full-size astronaut's spacesuit, and an aerospace engineer from Surrey Satellite systems.

Photo gallery

Links

Wednesday, 7 March 2018

Servicing a Skywatcher Powertank

My 7 Amp-hour powertank has unfortunately been out of action after I left the 12V power circuit switched on for a prolonged period. The battery never recharged to capacity and I replaced it with the Celestron Lithium powertank which has a very similar capacity (7.2 Ah) plus is lighter to carry. Its only drawback is not supporting a 12V cigarette lighter socket for CCD cameras or dew heaters.

The engineer in me hankered for a repair and so one evening last November I took the powertank apart with a Philips screwdriver for the 8 screws around the case, and a T-bar socket for the bolt holding the front lamp. The battery, a sealed lead-acid unit located in the base of the powertank, was easily removed. Rapid Electronics swiftly sent out a replacement and testing with a 30 Ohm dew strap (0.4A load at 12V) was a complete success.

Job done, and thanks to my brother for inspiring me to make the repair!