Cyclops Optical in Hong Kong has a new multispectral filter for imaging from light polluted cities:
https://www.cyclopsoptics.com/filter...pectra-filter/
I don't know much about it, just received an email from them about its release. The web page details its spectral profile and some example photos with and without it on the same target. Just pull up the Description link to see the spectrum and photos (page down).