light pollution

[Chippy3476]

Hi all,
How do you know how light poluted your sky is? Silly question I know but I only ever observe from my backyard and I can usually see alot of stars and objects with the naked eye, but sometimes objects are very faint through my 8 inch dob. Like the Sagittarius cluster is very faint but I can easily pick it out, so basicly is my sky ok for observing most objects? Is there a way to test light pollution?
Thanks all
Dan

[raymo]

The simplest way is to get a star atlas that shows the magnitudes of the
stars that it displays, and see what magnitude you can see down to. Basic
atlases that go down to mag 6 are quite cheap. You could probably
download and print one from the internet free. A dark site will allow you
to see stars down to around mag 5.5 to 6.5. I live on the edge of a small town, and looking over the town I can see down to around 4 to 4.5.
Looking away from town I can see down to around 4.5 to 5.
raymo

[Dboots]

Hi Dan,

I live in the hinterland of the Gold Coast so I am guessing that I have similar seeing conditions as Caboolture with the exception that my view to the south is superior to the view north and your's would be the other way.

I believe that the best test is judging what you can see with the naked eye. For example, on a very very good moonless winter's night, I can just make out the Lagoon Nebula, albeit through averted vision and after a good hour of dark adjustment. I can clearly see Omega Centauri on a moonless night. That said, I have never seen m31 with the naked eye because of the light pollution from Brisbane to the north.

You might be interested in the following link that explains the "Bortle Scale" for judging light pollution:

http://en.wikipedia.org/wiki/Bortle_scale

Duncan

[speach]

Have a look at this http://www.lightpollutionmap.info/#zoom=9&lat=-4633700.74949&lon=16222732.30022&layers=0BTFFFTT

[Ric]

Hi Dan

I'm quite lucky where I am out in the bush, I don't have light pollution at all. I am a 3 "Rural Sky" on the Bortle scale.

The night sky on a clear winters night is an absolute joy. :stargaze:

Cheers :)

[Dboots]

Hi Simon,

Thanks for the link. I'll add it to my favorites list.

Duncan

[Allan]

If you are really keen to know how dark your observing sites are and want to put a number on it, then you can buy a Sky Quality Meter. I like knowing which are the darkest of my dark sites. On the flip side, it gets depressing when you come home and take readings from your backyard.