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Mon, 07 Dec 2015 - Getting Ready for the Geminids (part 3) : Numbers

 

How to see the most Geminids:

As described in part 1 of this guide, these are the key points regarding the 2015 Geminids

-          Active Dec 7 - 16

-          Best nights Dec 13-14 and Dec 14-15

-          Best observed rates 10pm onwards

-          Find a dark observing Site

-          With a clear view of the night sky

-          Keep Warm

 

Here are some more tips regarding how you can maximise the number of Geminids that you see

Be Outdoors

Irrespective of the bullet points just mentioned, you won’t see any Geminids if stay indoors!

Given the frustrating behaviour of the UK weather, there is no sense in “saving your efforts” for the perfect time when the radiant is high in the sky on the night of maximum and risking that being clouded out. More often than not, it becomes a case of making the best of what is available. If the weather forecast suggests that it will cloud over by late evening, then do make use of earlier clear skies - you will not see as many Geminids but you will at least see some.

Where is the Geminid radiant? :  

This chart shows the location of the Geminid radiant. On the night of maximum it is near the star Castor.

In practice, the radiant isn’t a point in the sky, it is a circle a few degrees across.

Don’t look at Gemini

The temptation for newcomers to meteor observing is to look at the radiant area. Although more meteors will appear in this part of the sky, any that do appear will be travelling almost head-on towards you and as a result, their paths, when projected against the star background will be rather short and difficult to spot. I you look too far away from the radiant, however, the meteors will be too spread out and so you will see few.

The best compromise is to look at an area of sky centred around 30 degrees away from the radiant.

The likelihood is that the darkest part of the sky at your observing site is directly overhead. However, that is unlikely to be the area of the sky in which most meteors will be seen.

As the accompanying diagram shows, looking directly overhead, your field of view will only cover a relatively small amount volume of the meteor layer. If you look less high up in the sky, you will be viewing a larger volume of the meteor layer. If you look too low down in the sky however, you will be looking at parts of the sky affected by haze and by the glow from street lighting and this will more than counteract any benefit gained by further increases in volume of the meteor layer.

The best compromise is to look at an area of sky centred around 50 degrees above the horizon – from the UK this is an altitude similar to that of Polaris.

As a guide, the bright star Capella is just under 30 degrees distant from the Geminid radiant. Thus one area of sky around 30 degrees from the radiant will be that between Auriga and Perseus. This area of sky will be 50 degrees above the horizon around 8pm.

Similarly, the ‘bowl’ of the Plough is around 40 degrees distant from the Geminid radiant. Thus the area of sky below the bowl of the Plough will be around 30 degrees from the radiant. This area of sky will be 50 degrees above the horizon in the early hours of the morning.

Having quoted these 30 degree and 50 degree figures however, do allow your eyes to wander about a bit. If you stare too intently at the one part of the sky, your eyes become “bored” and lose sensitivity!  Aircraft or flashing satellites passing through your field of view can be distracting, so while they are passing by, look at a different part of the sky.

Stay Alert:  

At night, we are used to going to sleep and your body will be encouraging you to do this. The more that you are able to counteract this and to stay alert, the more meteors that you are likely to see. Having someone observe with you and chat with can help a great deal. In practice, it doesn’t make sense to observe for many hours without a break as your alertness will inevitably wane. Take a short break at least every two hours. Hopefully, though, Geminids should be appearing often enough to help you keep alert!

Keep Warm

As mentioned in part one of this guide, December nights can be very cold and you want to be focussing on seeing meteors rather than on how cold you are feeling. Hence make sure that you are well wrapped up against the cold. Having said that, a little discomfort from the cold can help you keep alert.

Keep Dark Adapted

If your eyes aren’t adapted to the dark, you will not see the fainter meteors – and faint meteors are more common than bright meteors. It will take around 15 minutes after going outdoors for your eyes to become reasonably well dark adapted, so you don't want to lose this sensitivity each time that you note down what you have just seen.

Use a dim red torch when recording what you see, so as to not spoil your dark adaption.

More Tips

These can be found in

http://www.popastro.com/meteor/observingmeteors/hintsandtips/index.php

 

Part 4 of this guide will describe how to record what you see

 

Added by: Tracie Heywood