Light pollution

Hi! Interesting idea. For visual observations and astrophotography thru telescopes , there are "light polution filters" commercially available. While they are meant to be screwed to your telescope's eyepiece or the optics of a CCD camera, you can even hold them in front of your eyes and get a better view of large nebula. Because that's what they are made for originally: observing nebula. Here is a nice article http://www.knoxvilleobservers.org/dsonline/tips/lprfilters.html However, doing photometry (visual or CCD/DSLR, whatever) thru one of these "light pollution filters" will of course influence the results. At least for narrow band filters that block almost all light except for some very small bands of wavelength, I guess the results would be difficult to transform into one of the standard bands (if at all possible). Maybe for broadband filters the result would be better. I guess it also depends on the kind of light that pollutes the sky: light from sources that emit at narrow bands of wavelengths (neon lights etc) might be easier to suppress in a way that still allows valid photometry, while light from "hot" light bulbs will be a mixure of wavelengths not unsimilar to the light of stars that we want to measure. That would be more difficult to suppress without ruining photometry of star light, I guess. CS HB