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

[Robert Harmon]

Michael,

Thanks for suggesting the Thuan-Gunn filter set. As you suggested in 
your earlier reply to my question, they don't seem to be available off 
the shelf. However, based on Wolfgang Renz's suggestion, I contacted 
Custom Scientific and asked if they can custom-make Thuan-Gunn filters 
threaded for my SBIG CFW-8 filter wheel. I was told that yes, they can 
do that, and that they will send me a quote in a few days. Maybe I can 
get Wal-Mart to pay for them! :)

Bob Harmon

Michael Newberry wrote:
> I responded to Bob Harmon's problem of low pressure sodium lights 
> brightening the V band by emission in the Na-I 5780A doublet (a.k.a., 
> the Fraunhofer "D" line"). I suggested he look into the Gunn-Thuan 
> uvgriz filter system. Today, Wolfgang Renz sent me somethig regarding 
> airglow brightening the background. So I should also add that the Gunn g 
> band (which is like a blue-shifted V filter) also cuts off below the 
> strong Nitrogen airglow line at 5577A. The filter set is well designed 
> for keeping a "dark" background.
> 
> Michael Newberry