Loads of data above, so you need a careful read, step by step. The above shows results that include the use of a UV/IR blocker, in ALL cases, i.e. visible wavelengths only. Hence if your modded camera does not have a UV/IR blocker at all (i.e. it has clear glass or nothing over the sensor) then you need to note that the Astronomik UHC filter needs to be used in series with a UV/IR blocker, otherwise it lets through oodles of IR. If, like in most mods, your camera does have a rectangular passband (so-called "astronomical") UV/IR blocker over the sensor, then the Astronomik UHC will give results similar to those shown.

There are two sequences displayed above: the top half starts with a domestic 100W Tungsten bulb, i.e. broad spectrum, and each line below the first imposes a filter of a more restrictive kind. Basically these demonstrate pictorially what each filter does. Pity that the tungsten bulb has little deep blue and violet and cannot fully illustrate what is going on at the violet end, an unavoidable limitation of rough science (and cheap light sources). The bottom half shows the same sequence but uses the Energy Saver light bulb.

The Hutech Idas LPS-P2 is the most sophisticated filter of the lot. Note that there is also a different LPS-V4 available that should not be confused with the LPS-P2. The LPS-V4 is similar to the Astronomik UHC+IR Blocker, but has a wider passband around OIII and a narrower one around Ha. The LPS-P2 is a notch filter that attempts to block only the strongest spectral lines emitted by street lighting (basically the strongest Mercury and Sodium lines) but freely pass the rest of the visible spectrum - as sophisticated as one can hope to be! How well does it do this? Simply look at the second-to-last spectrum illustrating what it does to a current-technology domestic "Energy Saver" bulb. I would say a very good job overall, but there are also all kinds of bright lines that are not blocked. These unblocked spectral lines, I presume, have been generated by esoteric phosphors or perhaps even proprietory gas mixtures. Recall that the bulb manufacturers' nirvana is to emulate broad-spectrum white-light, like a black-body radiation (or hot-filament tungsten) but at a high energy efficiency. Hot-filament bulbs have rather low efficiencies since much of the energy gets wasted in Infra Red and heat.

The 3rd line shows the effect of using the Astronomik CLS. This does clobber the rogue lines better (see its use with the energy saver bulb), but of course at the cost of mid-wavelengths and a detereoration in any possible "white balance". You can't have your cake and eat it... It does let through a reasonable amount of blue though, contrary to my expectations from just reading the published graph of its passbands. Hence I expect it to do almost as good a job at pale blue reflection nebulae like M45 as the LPS-P2. But the LPS-P2 ought to be the better choice for the more violet nebulae (like the Running Man, north of the Great Orion Nebula shown further on in this slides sequence), and definitely when one is chasing good white balance (imaging galaxies).

The 4th line shows the result of using the Astronomik UHC (in conjunction with a UV/IR Blocker). It is even more selective in its passbands. And these passbands do encompass both the Teal OIII and the deep Red H-alpha. The 5th and 6th lines show where OIII and Ha are located. Note that there is very little light emitted by the Energy Saver bulb that passes through the Ha filter. No wonder Ha narrowband captures in light-polluted suburbia are much more popular than OIII captures. OIII captures seem destined to be much more contaminated by fluorescent lighting.

You can gauge how effective each filter is in blocking the various strong emission lines of the Energy Saver lamp by working your way from the bottom. It is obvious that if you really do have massive light pollution, then the only sure way of rejecting almost all the light pollution is to use narrowband filters, like the OIII and the Ha. Next best is the Astronomik UHC(+ a UV/IR Blocker). This filter allows you to capture both OIII (and also Hb) and Ha (also SII)simultaneously. It's a double-the-speed way of doing narrowband imaging but at the risk of letting in some more skyfog. Basically it is a duo-tone filter that has a FWHM of 34nm (340 Angstroms) encompassing Hb and OIII in Blue/Green, and a FWHM passband of 43nm encompassing Ha and SII in Deep Red. Personally I would prefer a < 10nm passband on OIII and a similar one on Ha. Then I could ignore imaging using individual OIII and Ha filters altogether. But currently such a narrow duo-tone filter does not seem to be available in the market.

But just as our light pollution is ill-behaved, so alas are the nebulae. Many of the pretty nebulae we chase have more than just strictly Ha and/or OIII emissions. And therein lies the difficulty in choosing between the LPS-P2 and the CLS.