[Aavso-photometry] Low-pressure sodium lights and photometry

[Robert Harmon]

Hello, all,

I'm an astronomer at Ohio Wesleyan University, which is about 20 miles 
north of Columbus. OWU owns and operates Perkins Observatory 
(www.perkins-observatory.org), which houses a 32-inch reflector. Because 
it's f/17, it's not very useful for CCD photometry as the field of view 
is about 3x2 arcmin with our SBIG ST-8E. Thus, the telescope is used 
mostly for visual observing by students and the many visitors to our 
twice-weekly public programs. However, I do use 8-inch and 12-inch 
telescope on site for BVRI photometry.

To make a long story short, there is a strong possibility that a 
Wal-Mart Supercenter and a Toyota dealership will be built within a mile 
of the observatory to the south. The good news is that both would be on 
land annexed by the city (pop. ~22,000) in which OWU is located (the 
observatory is on the outskirts of town) and thus subject to lighting 
code restrictions which would require them to use low-pressure sodium 
lamps on 28-foot poles, as opposed to typical broad-spectrum parking lot 
lights on 40-foot poles. (Wait until the Toyota dealer sees what his 
cars look like under LPS light!) The bad news, of course, is that the 
lovely yellow glow will still most likely annihilate the naked-eye views 
from the observatory grounds and degrade telescopic views of objects 
like galaxies and clusters.

I have two questions for the list. Any insight would be greatly appreciated!

1. It seems to me that LPS lights should have a minimal effect on BRI 
photometry, but that V might be a different story. Am I correct in my 
thinking? Has anybody succeeded in doing good V-filter photometry in the 
presence of strong LPS skyglow? Any tips?

2. Does anybody know of references for estimating the level of skyglow 
from a given number of LPS lights at given wattages from a given 
distance? It would certainly help me make my case more effectively in 
community meetings if I could give some quantitative estimates of how 
bright the skyglow will be. Alternatively, does anybody know of any 
photos showing skyglow from LPS lights at a single large parking lot 
from a mile or a few miles away? There aren't any comparable facilities 
in my area.

Regards,
Bob Harmon