December’s talk was ‘Electronic Meteor Observing’, by Richard Fleet, who runs what he calls the Wilcot Station, which is in his garden, near the Salisbury Plain. And no, they are not electronic meteors; they are meteors that are detected electronically via the UK Meteor Observation Network (UKMON), and Richard is a welcome regular whose talks are always very interesting.
His latest talk revealed how easy it is for anyone to set up a really sensitive visual meteor observing station. His Wilcot setup consists of five CCTV cameras which are set up at various locations outside his house and in the garden. If you thought a DSLR camera would be more appropriate, stop. Remember that CCTV cameras are designed with high sensitivity in mind as they need to function in the dark, and they can give high speed video results, albeit with fairly low resolution (they would have a lens around f2, and don’t get the ones that are too wide angle). They can deliver mag 3-4 star brightness, which would take a DSLR camera about four seconds of exposure to record, but you must make sure you choose the ultra sensitive CCTV cameras.
CCTV cameras need a little heating element in the window, and the software he uses for monitoring is called ‘UFO Capture’. (No, just in case you’re asking, although he has caught owls, flies, spiders, moths, bats, etc.) When it’s on, the software dozes and is activated if it detects movement. It records at 25 frames a second so captures far more detail than a DSLR camera ever could. You can set them to ignore slow moving objects, such as the ISS, but you will still catch aircraft, moths and other wildlife, but it’s easy to delete the data.
You can leave it running all night, so can record a meteor shower quite comprehensively, although the composite pictures look a bit scatty because of various sporadic you’ll inevitably pick up and the meteor radiant will move considerably during the night. He recorded a whole night of Geminids, 180 meteors in total, and showed a composite shot of them on as seen from the ground. They seem all in a mess until you realise the radiant had moved right across the sky and background stars showed as very long faint trails.
Other interesting items viewed are cosmic rays, which are detected very briefly, unlike meteors, which will cover several frames. The rays will appear on one frame and sometimes have a little spray. Another rare phenomenon is a sprite, which are lightning flashes between clouds 80km up in space. They may last 1/20th of a second.
His five cameras are set up to cover the southern half of the sky, and his software enables him to calculate tracks and heights of the meteors. You can also calculate their orbits. Most of them burn up about 100km above the Earth and even the brightest fireball would only be the size of a grain of sand.
The UKMON network (20-25 cameras at 8-9 stations) covers the south of the UK but the 100km height of these burnups means he can see objects out over France and Ireland, so his recordings overlap with other stations out there. There are other stations in the North, such as at the University of Lancaster, and one called NEMETODE (NEtwork for MEteor Triangulation and Orbit DEtermination), which publishes its findings in the BAA journal.
He has liaised with a station in Graves, France, where they have a radio transmitter that bounces radio waves off the meteors. This means they can work in daytime and by the time you read this they will hopefully have been able to monitor the Quadrantids.
There are networks like UKMON all over the Earth. There is a large European network, EDMOND (European viDeo MeteOr Network Database. Cringeworthy). Between them, these groups have now identified over 250 meteor showers, 20 of them not known before.
Our own Ken Taylor followed on in the after tea talk by talking about radio meteor observing and said that 8 billion meteors hit the Earth every day, and that Graves uses a VHF radio that is also looking for bits of space junk.
As I write this the UKMON website is being revamped but it should be working by the time you read this. There is also a very good video recording covering most of this if you go onto the SPA website. The Society for Popular Astronomy has a website always worth dipping into.