Works well - could be a Baader clone though.Some emission nebula it works fine oetyers not so.Overall a positive result.

Very good narrowband filter for visual observations of nebulae. Effectively filters out light pollution. Got it at an excellent discount, great buy at that price. Good match for my other filters.

This filter is amazing... I’ve used it several times since buying it a few weeks ago... the filter allows you to see the finer datails of planets that you would normally miss... I live in a high light pollution area... the filter blocks it .. allowing you much better viewing

Increases contrast in Nebulae, some details will pop out which you would otherwise not know are there. You can now pick up NGC 2392. Without the filter, you would not even know it is there.

I can't compare this filter to its counterparts from Lumicon, Orion, Thousand Oaks, or others, since I don't own and haven't tried any of them. Physically, the Celestron looks identical those offered by Baader Planetarium--I've never seen any other make with those square serrations along the perimeter.We still haven't been out to our dark site with the O-III yet, but I did give it a quick try a few weeks ago at our local community college, where we usually just do planetary viewing due to the excessive light pollution. I inserted the O-III in our filter slide and pointed it toward M57, not expecting very much. After all, the Ring is supposedly better suited to a UHC filter than the O-III. The results were absolutely stunning--the nebula appeared as a distinct greenish ring against an inky black background. I then changed to a longer FL EP and directed our CPC 925 to slew over to M27. Usually we can't see the Dumbbell from the college and that night was no exception. Not knowing whether it was even in the FOV, I slid in the O-III filter and the nebula just popped right out, nearly dead center, and with as clear definition as we usually get from the dark site (Bortle's green) with no filter at all.We will definitely be picking up the UHC and h-beta filters to join this one. At more than twice the price, I can't imagine how the Lumicon O-III could be twice as good as this one, so I'm very satisfied with the Celestron filter, both in performance and value.UPDATE 7 Sep 2012: Well, it's nearly four years to the day since I bought this O-III and the other Celestron filters, and we've used them at multiple locations under suburban skies, as well as at our dark site. About the only thing I can add is that performance has been fully satisfying in every respect and each filter still looks as good as the day I received them, both optically and physically. I must admit, however, that they live a very pampered life--we use them exclusively in the power/filter slide on our EarthWin binoviewer, and I purchased several additional pairs of carriers so that I never have to swap any filter in & out of a carrier frame. Once mounted in its carrier, each unit only leaves its plastic case long enough to slide it into the binoviewer assembly. (The same carrier also fits newer Denks since they and EarthWin are co-owners on the patent for the power/filter slide system.)I was very surprised to see the 1-star review posted today by Allen Andrews, since my experience with this filter has been very positive. In fact, I dug out the original packaging for my O-III filter because I didn't remember it arriving in the kind of puzzle box that Allen describes. Sure enough, mine came in a clear plastic hinged storage box similar this one, but smaller: http://www.amazon.com/BCW-Trading-Capacity-Hinged-Holder/dp/B005KDHJBU/ref=pd_sim_sbs_sg_8. It was lined with a thin sheet of foam and the small plastic box was packed inside a slightly larger cardboard box. Fit and finish on the filter appeared flawless right out of the box and I screwed it onto a few different brand EPs and our 2" Zhumell Barlow just to make sure there were no problems with the threads before mounting it in the power/filter slide carrier frame. Allen's review makes me wonder if maybe Celestron is now using a new supplier for this filter and the quality isn't what it used to be. I would recommend that anyone considering this product consult reviews on the astro-vendor websites like Telescopes.com or OpticsPlanet.com, and maybe check the Cloudy Nights forums for any relevant discussion threads.I must also add that my own experience with Celestron products in general has been the exact opposite of Allen's. I have a Celestron CPC 925 GPS SCT purchased in 2007. It is one of the Chinese-made models, but it has been an exceptional scope in every regard: optically, mechanically, and electronically. I can't say the same for my three Meade scopes--two Newtonian reflectors and an ETX-125 Mak-Cas, all of which came out of the box with various defects ranging from clouded mirrors to faulty drive mechanisms and missing parts. A tripod foot cracked and broke on one of our very first outings with the ETX, even though we always set up on vibration isolation pads. However, I agree with Allen that you can't go wrong with any filter made by Tele Vue or Thousand Oaks, and I'd also add Lumicon to that list. For the money, though, I'm still very pleased with our Celestron nebula filters and OWL Astronomy color filters.