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...The long answer is that the only way to find out for sure is to measure it yourself. You are then faced with the dilemma of how to express that measurement in terms that will be meaningful to other people.

In my opinion, the best method to date is to use the Sky Quality Meter (Google for it). But this has to be used with great care, as it can be fooled by nearby streetlights or obstructions.

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Using VMag is a pretty universal method of expressing your LP. Here's a UMi VMag map you can use to figure your local naked-eye limiting magnitude; here's another for M45. Compare those numbers to the Bortle Scale NELM listings, and you'll have numbers everyone here will understand. Ain't perfect, as high thin haze, smog, dust, etc can all affect NELM - and those things have nothing to do with LP - but it gives you some idea. Keep a log, with an average, best, and worst. Over time, you'll have a good idea.

My area...

NELM between 3 and 4.3, average 3.5
Bortle class 9 (high 9, low 9, average 9... )
SQL 16.6 (low) to 17.68 (best ever, IIRC). Average 17.1

BTW - that 16.6 SQL was on a moonless night...
I have not bothered taking readings with the Moon up; there shouldn't be any questions as to why.

Now you know...

PS - A SQM can be a nice tool to have - or be very depressing...

Edit: On further thought, use the Bortle scale. NELM is dependent on your visual accuity; your NELM 6 may be my NELM 5. Just a thought...

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In the Land of Eternal Light Pollution & Great Pizza (Chicago)

SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...



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Edited by Joe Cipriano (03/18/08 07:56 PM)

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