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  #21  
Old 01-08-2013, 06:36 PM
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mental4astro (Alexander)
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Hmmm, Omega Optical apparently makes filters for other brands, big ticket brands. It could be that their OIII/Hb is one of those. After all, they have the capacity to produce their own premium in with their DGM line, a cut price 'home brand' just covers the lower end.

Either way, I'm happy with the performance of the OIII/Hb filter of theirs. Performs differently from the NPB I have, like an OIII would.

If premium prices are out of reach, or not important to one, the more modestly priced filters will still do a good job. You won't be looking into soup if that's what worries. But, I do think being properly informed is most important, regardless of one's ultimate choice. Picked up a couple of things too myself,
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  #22  
Old 01-08-2013, 11:54 PM
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The original narrowband filter, designed by Jack Marling of Lumicon, covered the H-beta and O-III lines emitted by gaseous nebulae with a bandwidth at FWHM (full-width, half maximum) of 23nm, approximately. The DGM NPB covers those wavelengths with a slightly narrower bandwidth. The purpose was to provide enhancement for nebulae while seriously darkening the background sky.

Marling also designed filters to cover just the H-Beta (about 9nm bandwidth) and just the O-III lines (about 12nm bandwidth), which he called H-Beta and O-III filters respectively. For study of those emission lines in certain nebulae. The O-III filter, specifically, was and is particularly successful at enhancing planetary nebulae.

An O-III filter can have up to about a 15nm bandwidth and still be considered an "O-III" filter, i.e. a filter that just passes the O-III lines in the spectrum and not much else, the goal being to enhance the contrast between the O-III emission lines and the background sky.

The link to the "O-III+Hb" filter shows a filter with about a 60nm FWHM bandwidth, which would not be considered an O-III filter by any company making them today. It wouldn't even be considered a narrowband filter (like Lumicon's UHC or DGM's NPB or Orion's Ultrablock) because the bandwidth is too wide.

At that bandwidth, it is similar to Baader's UHC-S, which sort of bridges the gap between a broadband filter (also known as a light pollution reduction filter) and a Narrowband filter (previously mentioned).

Since there are now a few filters with that wider bandwidth, we should probably refer to them as "wideband" filters to differentiate them from narrowband filters. They pass the O-III and H-Beta emission lines, for sure, but too much more to be considered a narrowband "nebula" filter.

I suspect they would do quite well when the sky is already really dark. And they wouldn't cause so many stars to disappear, which might be an aesthetically-chosen option.

The broadband, or LPR filter will have an even wider bandwidth, removing most of the deep yellow, orange, and shorter wavelength red, is made by many companies. The enhancement of nebulae is minor, sort of like turning up the contrast from 3 to 4 on a ten point scale. They work decently for photography and can be a "guilty pleasure" at a really dark site by turning up the contrast a bit without sacrificing all the stars in the field.

There are about 40 brands of filters out there now, and while the "wideband" filter could definitely be in the arsenal of nebula filters (especially for very small apertures), its reduced utility as a "nebula filter" would prompt me to suggest a narrowband as every observer's first nebula filter. There are many good ones (I've mentioned a few), but the one in the link is not one.
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  #23  
Old 02-08-2013, 08:31 PM
glend (Glen)
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Thanks folks and especially Don P for that very complete review. I've been lurking in the background on this thread while I researched my first filter for visual observing with my 12" dob, and I checked out the cloudynights link and noticed this comment:

David K's review of the DGM NPB filter showed that he was getting better contrast consistently with this filter over the Lumicon UHC. He then goes on to say, "The DGM Optics NPB Filter is an excellent narrow-band nebula filter which I recommend that nearly every amateur have in their eyepiece box."

Good enough for me, I've bought one.
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  #24  
Old 07-08-2013, 05:15 PM
bytor666
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Hmmm, Omega Optical apparently makes filters for other brands, big ticket brands. It could be that their OIII/Hb is one of those. After all, they have the capacity to produce their own premium in with their DGM line, a cut price 'home brand' just covers the lower end.

Either way, I'm happy with the performance of the OIII/Hb filter of theirs. Performs differently from the NPB I have, like an OIII would.

If premium prices are out of reach, or not important to one, the more modestly priced filters will still do a good job. You won't be looking into soup if that's what worries. But, I do think being properly informed is most important, regardless of one's ultimate choice. Picked up a couple of things too myself.
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  #25  
Old 07-08-2013, 05:16 PM
bytor666
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Quote:
Originally Posted by bytor666 View Post
Hmmm, Omega Optical apparently makes filters for other brands, big ticket brands. It could be that their OIII/Hb is one of those. After all, they have the capacity to produce their own premium in with their DGM line, a cut price 'home brand' just covers the lower end.

Either way, I'm happy with the performance of the OIII/Hb filter of theirs. Performs differently from the NPB I have, like an OIII would.

If premium prices are out of reach, or not important to one, the more modestly priced filters will still do a good job. You won't be looking into soup if that's what worries. But, I do think being properly informed is most important, regardless of one's ultimate choice. Picked up a couple of things too myself.
Alex,

A friend and myself did a shootout between the Omega / DGM O-III and an Orion Ultrablock and there was no difference at all !!!
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  #26  
Old 30-08-2013, 08:09 PM
knightrider
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Has anyone had any experience on Prostar filters.
I've tried finding reviews or manufacturing information but can't find anything on them. From what I see they rebrand various products but try and provide value for money.

I was looking at their narrowband filter here: http://www.myastroshop.com.au/produc...p?id=MAS-001B3

Opinions? The only information I find is their own filter guide.
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  #27  
Old 04-09-2013, 07:50 AM
JJDOBBER79 (Jas)
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I also bought the DGM NBP in the 1.25" for use with my 6" dob. My limited understanding is that this filter will become more useful as aperture increases. On the 6" I can notice a very slight contrast improvement on nebula, but not a whole lot. Thinking of upgrading aperture soon so hopefully will get more use out of it.
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  #28  
Old 04-09-2013, 05:03 PM
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I've owned a lumicon uhc , orion ultrablock and now a DGM NBP
I find the dgm very differant to the other two both the lumicon and orion did a good job on enhancing different nebula, the dgm seems quite different in that it doesn't seem to throw up such the stark view and detail of the other two, anyone experience anything similar?

Last edited by GrahamL; 04-09-2013 at 05:34 PM.
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  #29  
Old 05-11-2013, 12:00 PM
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mental4astro (Alexander)
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So, what can the Omega Optical OIII + Hb filter really do?

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.

Last edited by mental4astro; 05-11-2013 at 01:03 PM.
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  #30  
Old 05-11-2013, 01:03 PM
glend (Glen)
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I have a DGM NPB filter that I use with my new 16" dob and I love the detail that it brings to life in nebula like Orion and Tarantula - at a truely dark site like Bretti. I have used it at home but feel to really work well it has to be used under very dark skies.
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  #31  
Old 07-11-2013, 01:46 PM
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gaa_ian (Ian)
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This may be of interest for those looking for either a 1.25" or 2" UHC
I have found these UHC filters quite effective on increasing the contrast and extent of nebulosity visible at least on the Orion Nebula through an 8" Dob.
There is a link to the bandpass specs with the filter listing.
And yes (in the interests of disclosure) I am selling these filters, which are the same spec as those sold by "Orion"
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