[mental4astro (Alexander)]

Last Sunday night I was finally able to do a side by side comparison of each of my three 2” filters. These are an Omega Optical Hb, a DGM NPB, and the Omega Optical OIII + Hb filter I mentioned earlier in this thread. The test target was the Horsehead nebula - if any nebula was going to sort the men from the boys it was this one. The scope used was my 17.5" dob.

The view through the Hb filter was the darkest. As to be expected as it is the narrowest band filter of the three. Seeing the Horsehead pillar was an exercise in seeing black on black. The glow of the background gas the pillar sits on is only just slightly brighter than the rest of the field. Once you knew where to look for the pillar it was quite striking, but by no means ripping your eyeball out obvious.

Next used was the NPB filter. Slightly wider band through put, so the whole field was a brighter, and so to spot the Horsehead, I’d say a little less contrast too. Yet, it was visible, and made easier knowing where to look.

Last was the OIII + Hb. I nearly didn’t use it thinking of Don’s words, but I thought ‘what the heck – let’s have a shot’. Well, the field again is slightly brighter than that of the NPB, and a lot more stars were visible, but, more importantly, the Horsehead WAS VISIBLE! And just as easy to spot as in the NPB!

Now, these observations were are not just my own. Jason, Steffen (who have added their voices to this thread) and Ed were there with me at Katoomba Airfield, and all looked through each of these filters. Now armed with verified practical experience on the OIII + Hb filter, and can most whole heartedly recommend it as a bloody good filter. Not theoretical scoffing at the labelled capability of the filter, but actual visual experience. It does as it claims. Interesting that no one has actually put down their experiences with this filter, but felt justified to dismiss it outright.

My hat off to Omega Optical in producing such a capable filter, AND at such an affordable price.

NB: Katoomba Airfield is 100km west of Sydney’s CBD at 1000m above sea level. Skies, while not text book perfect due to the proximity to Sydney, still provides excellent conditions due to its elevation. It certainly is good enough to allow us to see the Horsehead pillar without any major problem.

Mental.

PS: Don, your suggestion that the OIII +Hb filter would show more stars was very much correct. What is interesting is that while it may not strictly be a narrow band filter, it performed like one.

Mark, yep, I'd have to agree with your friends about the performance compariso, though I did find a slight difference, & I find the OIII +Hb visually more appealing.