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Star trails at Hardraw

Credit: Megan

The village of Hardraw is pretty dark. On the Philip's Dark Sky Map of the UK it lies in a patch of blue which corresponds to a visual limiting magnitude of 5.5 to 5.75. The theoretical limiting magnitude of the average human eye under perfectly dark conditions is about magnitude 6, so Hardraw is petty good. (One of the things about astronomy is it's slightly bizarre measurements, mostly due to the fact that astronomy is such an old science. Magnitudes get larger as objects get fainter, so magnitude -27, the apparent brightness of the Sun, is brighter than magnitude 0, the apparent magnitude of a star such as Vega, which is brighter than magnitude 6.)

Malcolm, one of our members, gave me a lift up on Friday afternoon, and during the drive up the weather looked very promising. Most of the way we had clear skies and sunshine, until we got north of Lancaster and into the Yorkshire Dales National Park at which point we encountered thick grey cloud. Typical. Still, we were not too upset as we've had worse evenings turn out reasonably. Sure enough, by sunset the skies were clearing slightly and most people had set up their telescopes just in case. The sky was patchy for quite a while but that gave us plenty of opportunity to investigate the range of equipment that had been brought along. There were short-tube refractors, large schmidt-cassegrains and a few newtonians, as well as several different styles of camera.

A quadrifilar helicoidal antenna

Credit: Kevin G. Shea

My favourite was Alan's new aerial: a quadrifilar helicoidal antenna which is used to pick up weather satellite transmissions at 137 MHz. It's a beautiful-looking piece of technology, a helical structure constructed from copper piping that looked something like the image on the right.The signal is sent through a hand-held scanner, the output of which is fed into a computer using the soundcard line in as an analogue to digital converter. Some software then takes this signal and translates it into an image, similar to the way a fax machine works. When he set up for the first time we heard the satellite through the speaker on the scanner and the software appeared to be receiving data, although the picture on the screen looked rather like noise. After the satellite had passed below the horizon the data was processed a bit and we got an image. It may have been cloudy in Hardraw, but the skies were clear over Sicily!

After that, the skies cleared up nicely and we were treated to some of the best seeing conditions we have ever had. The Milky Way was easily visible rising in the east underneath Perseus, running overhead through Cassiopeia, Cygnus and Aquila, and setting behind the hills in the west. There is so little light pollution there that the Galaxy can be seen almost to the horizon. While some chose to recline in deck chairs watching for Perseids, others spent the evening hunting for faint deep sky objects. I spent most of the evening sat on the wall with my camera taking time exposures of the Galaxy, accompanied by a soundtrack composed of a baseline of whirring motors, periodic calls asking if anyone wanted to see such-and-such an object, and a chorus of "oooh!"'s and "ahhh!"'s as meteors flew overhead. The Perseids put on a good show this year. There were many faint ones, and several really bright ones that left glowing trails that persisted for several seconds in some cases. One was even seen to break up as it appeared to fall towards the roof of the hut.

Saturday dawned cloudy and wet. Making the most of being out of Manchester for a bit, I decided to go for a walk, even though the weather was gloomy. The Pennine Way runs up the track beside the hut so I headed off up Great Shunner Fell in the occasional downpour. I got to the top as the cloud descended so turned around and wandered back in the general direction of the village. As I got back, the sun made an appearance so out came the solar telescopes (you don't go on an observing weekend expecting to get any sleep!). Unfortunately the break in the weather was temporary and the clouds were back by the time we had finished dinner.

Despite the cloud, it was still a great weekend. The sky on Friday night really was one of the most spectacular sights I have seen in a long time. Rarely is the seeing that good, and for that to coincide with a night when we happen to be far from any light pollution was really, really lucky.

MAS at Hardraw, August 2005
Roll on October! Credit: Megan Disclaimer

Posted by Megan on Sunday 14th Aug 2005 (20:33 UTC) | Add a comment | Permalink


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