stacking light pollution filters

[Madhatter]

Just wondering if stacking two of the same filters (skywatcher lp 1.25/2" ) would have any benifits..

i am guessing not as they cut out specific light wavelengths, but just thought id ask.

[LukeSkywatcher]

I think it would have no benefit and would only make your image darker overall.

[Ags]

Let's say one filter cuts out 10 percent of good light and 95 percent of a couple of pollution wavelengths. Two filters would cut out 19 percent of good light (twice as bad) and 99 percent of the pollution (a meagre 4 percent change).

[Psychobilly]

In the ideal world ignoring surface losses you would multiply the transmission at each wavelength when combining filters...

I have used the technique in the past in specialist light sources... Schott used to provide you with a database of their available glass types and an app to stack them...

These days more complex dielectric filter stacks can be produced...at a cost...

[Madhatter]

Ok thanks guys, just wondered really:) cant wait to try out the filters though, living in a fairly light polluted area i am hoping it will make some differance.

[LukeSkywatcher]

The SW LPF is a good one. I can aim my scope right between 2 street lights across the road and you would hardly even know they are there.

[Madhatter]

excellent!! i think all the lights by me are sodium lights too so should deffinatly notice some differance, just need to wait for the clouds to shift now.