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Dazzyd

How far away from the town light to travel?

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Hi all

How far away from the town/city lights do you think I need to travel to get some decent viewing? I live in the West Midlands (DY2 area) so it's quite light polluted and would love to get somewhere darker and clearer. Haven't got a scope right now but I have a pair of Celestron 15x70 bins (thinking about maybe going to the 20x80 pair) and I'd also love to get some nice photos that aren't so orangey from the street lighting.

Thanks

Daz :-)

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Looks like out past Bridgnorth is where you need to head

Edited by rockystar

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It's not just a question of how far, but also the direction. You do not want to have a major source of LP on your Southern horizon.

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I posted this thread recently, asking about dark sky locations in Shropshire.

http://stargazerslounge.com/topic/256786-dark-sky-locations-in-shropshire/

Some very good suggestions on it. I'm planning to head west of Church Stretton for my next dark site trip.

I definitely want to venture out to Mid or North Wales eventually too.

Andy.

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It's not just a question of how far, but also the direction. You do not want to have a major source of LP on your Southern horizon.

Great point. I occasionally travel just a couple of miles north to get to a generally darker site. You don't need to go far to make a noticeable difference (depending where you're starting from). But, if I particularly want to view southern targets in darker skies, then I'd travel perhaps 10 miles west, so that the glow from town is off to one side.

Also, I wouldn't bother to travel anywhere while the moon is bright.

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Various models have been proposed for the percentage increase in sky brightness above the natural level, I, as a function of town population P, distance from town, d, and other factors. One simple (crude) model is

I = 0.01Pd-2.5

which gives the percentage increase at altitude 45 degrees in direction of source (quoted from Bob Mizon: Light Pollution - Sources and Remedies, p66). This of course assumes there is only one town producing the light: in most of Britain that's not a reasonable approximation. It also makes an assumption about the amount of light per person, which breaks down for large cities.

The model suggests that a town of 3000 people will cause significant light pollution up to about 10km away. For a population centre of a million people it implies 10% skyglow 100km away, but that is an underestimate. Light pollution from Glasgow is visible at dark sites in Northern Ireland.

In practice one tends to find that as distance increases the gain in sky darkness starts to become less pronounced, so there is a balance to be struck, going just far enough that it makes a worthwhile difference, and not going miles further with little extra gain. That depends on the particular local situation and one's own needs, and is found by trial and error.

Edited by acey
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It's not just a question of how far, but also the direction. You do not want to have a major source of LP on your Southern horizon.

Hey laudropb, I see you are in Glasgow close to me in Coatbridge.  Using the LP map, it looks like just north of the Campsies close to the Fintry junction would be a good place close to us to use for observing but you raise a very pertinent point about not having LP on the southern horizon.

The back of the Campsies obviously means Glasgow is directly to your South, however do you think the Campsies could act as a natural barrier to the LP from Glasgow, making Fintry a suitable viewing area?

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Based on these maps, I've found what looks like VERY dark skies relatively close to me... But... where do I park?

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