Just a check on which filter is better for pale blue reflection nebulae like M45. NB: While M45 is often referred to as "blue", it is apparently simply bluish-white (hot) starlight that is reflected off the nebulae. The primary result is that they are both quite useless with high light pollution on the pale blue wispy stuff. Presumably "pale" implies significant white content. Despite 31 minutes integration time using a C14 on each of the above stacks (top pair), it's quite obvious that hardly any nebulosity was recorded. The Visual Limiting Magnitude was at around 3.5, measured at zenith by the Unihedron Sky Quality Meter at Mag 17.6/sq arc-sec. Absurdly aggressive stretching yielded the bottom pair. Conclusion? Both filters are ineffective under said conditions, specifically, very high skyfog and pale blue nebulae. I am left with the suspicion that no filter at all, just a UV/IR blocker, may well do a better job. This is NOT to say that both filters are useless for other stuff. On the right target they can work wonders. I have shot a mixed emission nebula from the same light-polluted location and I think the result does show that the LPS-P2 can indeed be quite useful even with a VLMag 3.5 skyfog, see previous slide. Unfortunately I have not gotten around to try a similar target with the CLS but I have no reason to doubt its efficacy on emissive nebulae. The experiment presented here above had a strict objective: Compare these 2 filters on M45 under high light pollution. Period. Both seem quite ineffective and as such this little investigation does not aid those who are in the throes of deciding which one of the two filters to purchase as a "general purpose" filter. My own sentiments, with the continued lack of corroboration from back-to-back field testing, remain with the LPS-P2 as a good, multi-purpose, white-light filter for moderate light pollution, VLMag 4.5 skies or darker.

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