25 YEARS
1985 - 2010
Letchworth & District Astronomical Society
Meteor Watching

 

What are meteors?

One astronomical activity that anyone can take part in is watching meteors. You don't need any equipment other than your eyes - in fact telescopes and even binoculars may be useless because they will cover too small an area of the sky, and meteors move fast!

Meteors are what are often called "shooting stars", although there could hardly be a greater contrast. Real stars are gigantic globes of gas that burn through nuclear reactions, whereas meteors are usually only tiny specks of dust!

In that case, why are they called "shooting stars" and how is it that we can see them? Well it is down to the fact that they - and the Earth - are travelling very fast through space. As our planet speeds in its obit around the sun, it sometimes passes through clouds of dust which are leftover from the tails of comets. As these particles travel through the Earth's atmosphere, friction makes them heat up. You can see this for yourself by rubbing your hands together - friction is what makes them feel warm, but you'll only be rubbing them quite slowly - meteors can be travelling at several miles per second! As a result, the heat from the friction is so great that they burn up, and it's the glow from their fiery destruction that makes them bright enough to be seen from the ground.

As they speed across ovehead - usually only taking a few seconds, they look like stars shooting across the sky - hence the name.

Sometimes they are big enough to survive their journey through the atmosphere and the part that is left over and hits the Earth is called a meteorite. Occasionally there can be quite big meteorites, such as the one that caused the famous Meteor Crater in Arizona, or the even bigger one that crahed into the Earth 65 million years ago and wiped out the dinosaurs!

So what are we going to be doing?

There are several major meteor showers each year. These are times when we pass through a comet's particle stream and for a few nights there are a fair number of meteors visible. The number various from one shower to another, and also from year to year. What you can see also depends on how dark the sky is and in 2008 the glare from the Moon made meteor watching quite poor. However in 2009 prospects were much better. The forecast for 2010 isn't quite as good, but we are planning for two meteor watch sessions this year, on the following dates;

Date Time Meteor shower ZHR
Thursday August 12 From 20:00 Perseids
80
Monday December 13 From 19:00 Geminids
100

What do the names mean?

The meteor showers get their names from the constellation that lies in the direction from which they appear to come. This point is called the "radiant", as they appear to radiate from that location. For example, the meteors in the main shower in August appear to come from the direction of the constellation of Perseus, so they are called the Perseids. The others listed above have their radiant in Gemini.

In fact they are nothing to do wth the constellations; that is simply the pattern of stars which lie in that particular direction at the time.

How can we observe meteors?

All that's needed is to look up at the sky! Of course it's useful to know from which direction the meteors are going to appear, but that doesn't mean that it's best to look in that direction. It can be better to look about 90º away from the radiant.

As this involves looking upwards for long periods, the best way of doing this - and avoiding a stiff neck - is to lie down on a chair - preferably a recliner. As you'll be doing this for some time, here's a checklist of what you might want to bring:

  • A reclining chair - You want to be comfortable. An alternative would be a li-lo or something similar.
  • A hat - most heat loss from the body is through the head.
  • Gloves
  • A good pair of shoes or boots to keet your feet warm.
  • Good thick socks, or 2 pairs of thin ones!
  • Possibly a blanket to (a) insulate you from the chair and (b) to wrap over you.
  • A flask with a hot drink
  • Some nibbles to keep you going through the night!

If you want to make a record of your observations, then you might also want the following:

  • A notebook and pen
  • A camera and tripod (see below)
  • A torch - Make sure that you cover the end with red plastic or cellophane to prevent the brightness from ruining peoples' night vision.

How many meteors will I see?

This can vary enormously. The table above gives the predicted Zenith Hourly Rate, but actual rates are likely to be lower than this.

How can I take photos of meteors?

There are two things to remember - meteor trails are faint and you can't guarrantee exactly when or where they will appear.

So the best thing to do is to take a series of long exposures of the sky. To do this you need a digital camera - so you can take lots of pictures and then delete the ones that don't show any meteors - which will be most of them!

You will need to set the camere on a tripod or place it on something so that it is pointing in the required direction, and have it set to take long exposures. Most cameras will allow exposures of 30 seconds or more. Do watch out, though, as some need about the same length of time as the exposure to process the image before saving it. You also want to be able to start the exposure and not to have to hold the camera whilst the image is being captured, or you are likely to finish up with a very wobbly picture!

Depending on the meteor rate, you may want to take one picture per minute or so, so you will probably need at least one extra set of batteries. We can provide additional information on watching and photographing meteors when you book.

So your checklist for photographing meteors should include the following:

  • A digital camera that can take long exposures
  • A tripod or some way of fixing the camer to ppoint in the required direction
  • Spare batteries
  • Perhaps an extra memory card

How do I take part?

Simply let us know that you'd like to come along to a particuar session by sending a message to events-at-ldas.org.uk (Replace "-at-" with "@")

Then come to Standalone Farm on the given night and we'll show you where to park and set up.

There is no charge for this activity.

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LDAS is affiliated to

British Astronomical Association

Federation of Astronomical Societies

Society for Popular Astronomy