How dark is dark?

[LAW]

I've had my scope for a few months now and I've just been setting it up in my residential backyard which has been great. We're far enough out of the city that the galactic plane is clearly visible and there are loads of clusters/nebulae I can see too. But last night I drove out to may mate's inlaws place which is a further hour away from the city in a rural area.

The problem was that even though it was dark, the sky was roughly the same, M6/7 clearly visible, I could see the dark lanes in the Triffid nebula through my 8" newtonian but not much more detail than I get in my own backyard.

I've been to Coonabarabran a few times and the sky there is fantastic, how far out of town do I have to go before the light pollution starts to drop away?

[loki78]

Hey Murphy,

Have a look at this:

http://googlemapsmania.blogspot.com.au/2011/12/light-pollution-on-google-maps.html

Click on the map and then compare the colour of the area where you live, where your mate lives, and then Coonabarabran and it might give you an idea.

Let us know what you find!

[LAW]

Thanks for the link. That's cool!
Yeah we were in very similar areas, his is slightly darker but there was a few patches of cloud so maybe the seeing just wasn't great last night. Although according to their scale, Coonabarabran is about the same so it doesn't seem particularly accurate, an interesting comparison nonetheless.

[loki78]

I think off that map, not just what you're in at the time, but the proximity of brighter areas as well. Coonabarabran has nothing bright anywhere near it really whereas if you're on the border of a bright area that will affect you.

[LAW]

Yeah that makes sense, it drops off pretty quick past the mountains. I can feel a road trip coming on... :D

[naskies]

Moisture, fog, and clouds can make a big difference too, by reflecting light from far away towns.

I've been out to Roma / Mitchell a couple of times for stargazing: one on night, it was stunningly dark (summer Milky Way casts a visible shadow on the ground) but a few days later there was a visible glow to the sky.

[mickyj]

This is very cool. Thanks.