57 replies to this topic

[tommm]

What works better for most nebulae in light polluted skies, UHC or OIII filter (Astronomik or Lumicon Gen.3 OIII)?

[Galaxyhunter]

In my experience,  The Olll does a good job.

[sg6]

Little in it I would suggest.

A UHC is likely passing OIII and Hb in the blue/green spectrum, and also some Ha and SII at the red end. Your night vision may however wipe out the red end stuff.

 

Will say some UHC's pass only at the OIII+Hb portion and no Ha+SII red stuff.

 

The OIII will or should be narrower and block Hb so would be dimmer on the eye.

 

I would likely search out a UHC that passes just OIII and Hb.

Or go for the straight OIII.

[havasman]

It depends on the emission spectrum of the nebula. Matching the passband frequencies of the filter to the emission spectrum of the nebula is what yields increased apparent contrast of the object against the sky darkened y the effectiveness of the filter.

 

You are going to end up wanting both narrowband UHC and O-III filters to best show the range of emission nebulae you will eventually want to observe, definitely including the wealth of nebulae now showing in the summer sky. It is almost universally recommended that a UHC filter is the better first purchase as it has a broader range of applications. But the added flexibility and utility of an O-III is undeniable. I am in a dark part of SW Texas this week and nebulae have been a significant part of the week's observing. I have used both UHC and O-III extensively for different objects and have also played around with using the "wrong" filter for several objects. Generally the commonly recommended best matched filter has proven why it is recommended.

 

Both filter suppliers you list are top rank performers. I use Lumicon UHC and their Gen 3 O-III but Astronomic are also very good narrowband filters. Current Televue filters also belong in the top class of nebula filters.

 

Neither Ha nor SII are significantly relevant emission lines for visual observing.

 

All good nebula filters will work better from under a dark sky.

[spereira]

Moving to DSO ...

 

smp

[Astro-Master]

My favorite filter when I choose to use one is the DGM NPB it seems to be in between an OIII and a UHC to my eye.  I like to view the nebula with the stars in the background, the OIII dims the stars too much for most objects.

 

When I'm using my 18" Dob. in dark skies I usually don't use a filter on the brighter nebula, M8, M20, M17, M27, M57, ect, I find the image is bright enough, and the star fields look better without a filter.  Using the 18" on Planetary Nebula I use high power 500x to 1,000x or more when the seeing allows to see the fine detail, and a filter just dims the image at that power.

 

  My favorite object with the NPB filter is Thor's Helmet, NGC 2359, it really pops with this filter IMHO.

[Dave Mitsky]

Here's how David Knisely ranked the filters in his comparison at https://www.prairiea...common-nebulae/

RECOMMENDATION RANKING SUMMARY

 

UHC best on 41 nebulae, close second best on 47 nebulae.

 

TOTAL 1st and 2nd RECOMMENDATIONS for UHC: 88 objects.

 

OIII best on 34 nebulae (biased by the inclusion of some planetary nebulae),

close second best on 22 nebulae.  *NOT* recommended on 6 nebulae.

 

TOTAL 1st and 2nd RECOMMENDATIONS for OIII: 56 objects.

 

H-BETA best on 16 nebulae, second best on 2 nebulae.

 

*NOT* recommended on 39 nebulae!

 

TOTAL 1st and 2nd RECOMMENDATIONS for H-Beta: 18 objects.

 

DEEP-SKY best on 7 nebulae, second best on 3 nebulae.

 

*Provided at least some slight improvement for *all* nebulae surveyed.

 

TOTAL 1st and 2nd RECOMMENDATIONS for DEEP-SKY: 10 objects.

[MarMax]

I'm a fairly new owner of a TeleVue Bandmate-II O-III and a Lumicon Gen3 UHC. Bought them both at the same time from Don Pensack. I've also seen all the recommendations for which nebula look best with which filter and my impression is that both of these filters work well. I've only viewed a small portion of the nebulas so far but for those that the UHC is recommended the O-III works well and for those the O-III is recommended the UHC works well.

 

You probably don't need both but if you don't mind spending $400 you might as well get both. For visual observations the filters really do make things spectacular. I've not tried to use them with photography (yet).

[Tony Flanders]

What works better for most nebulae in light polluted skies, UHC or OIII filter (Astronomik or Lumicon Gen.3 OIII)?

In light-polluted skies you're likely to be happier with a UHC, is my guess. That's not so much because of the nebulae that you're viewing but because of the stars surrounding and embedded in it. Under bright skies, there are already too few stars for comfort in any given eyepiece view. Both O-III and UHC filters suppress stars, but O-III filers suppress them more. Using my 70-mm refractor with an O-III filter from the middle of a city, my eyepiece fields sometimes contain no stars whatsoever, which is rather disorienting.

[cuzimthedad]

I'm a proponent that if you can afford both, then do it. I do, in 1.25" and 2" but again, that's just me.

[Corcaroli78]

What works better for most nebulae in light polluted skies, UHC or OIII filter (Astronomik or Lumicon Gen.3 OIII)?

I own both (from ES) and for me (100% visual rich field), the O-III is by far more helpful than the UHC

 

Carlos

[KTAZ]

I bought my UHC first and will buy my OIII next. As noted earlier, the UHC will take first place on the most objects with OIII taking second. However, UHC will also still perform well on many of those OIII objects, some just as well, and some not quite as well.

 

The UHC is the best first choice IMHO.

Edited by KTAZ, 21 August 2020 - 03:58 PM.

[chrysalis]

I would also add in my vote for a narrow pass band filter.

 

I have the Lumicon and DGM versions of both the NPB and OIII filters. OIII is too aggressive in removing light for my eyes. The Lumicon OIII almost never leaves the little case, the UHC only slightly more often.

 

Regarding the NPB filters (Lumicon UHC, DGM NPB), the Lumicon does not pass the red wavelengths and so stars are cyan and the overall field is darker. DGM NPB passes the red, and so stars appear with a pinkish cast and the field in overall brighter. I find the view through the DGM NPB to be more aesthetically pleasing.

[havasman]

Moving to DSO ...

 

smp

Why not EYEPIECES which is specifically described as "A place to discuss our favorite eyepieces and eyepiece accessories, barlows, filters, etc." in the frontspiece?

Edited by havasman, 21 August 2020 - 08:39 PM.

[Feidb]

I happen to have both myself. Actually, I have the H-beta as well. I end up using the UHC as often as not. The O-III definitely works its magic on certain objects but then again, sometimes the UHC works better. On the other hand, just as often, I use BOTH on the same object to see different features. Sometimes all three.

 

If I were to choose one, it would be a tough call because the first one I got originally was the O-III and it opened up a whole new world for me. Then again, that was way before the UHCs really existed.

 

Now, I'd probably follow Dave Knisleys recommendation and go for the UHC first.

[Dave Mitsky]

Keep in mind that UHC (Ultra High Contrast) is Lumicon's propriety term, if that's the correct way of putting it, which eventually was co-opted by other companies.  This type of filter is better referred to as a narrowband nebula filter.

[Redbetter]

What works better for most nebulae in light polluted skies, UHC or OIII filter (Astronomik or Lumicon Gen.3 OIII)?

Based on the underlined bits, a quality line filter will likely provide the best views for the conditions for the following reasons:

• Most bright emission nebula are strongest in OIII.  In light polluted conditions these higher surface brightness nebulae are preferred targets.
• Nebulae dominated by H-beta emissions tend to be lower surface brightness and are therefore poor targets for light polluted skies even with filters.
• Line filters have about 50 to 60% of the bandpass of a good UHC/narrow pass filter.  In light polluted conditions removing unwanted "noise" is usually more important than transmission in secondary bands. 

In darker sky conditions there is more reason to use a narrow pass filter rather than a line filter, so as to retain more of the weaker signal rather than sacrificing it in order to remove more light pollution background noise.  And the closer to pristine conditions are, the less need there is for a filter at all, except to enhance the contrast of the lowest surface brightness portions relative to the sky or screen out other bands so that specific emission features are seen (e.g. the dark silhouette of the horse head against the surrounding H-beta emissions.)

[Jon Isaacs]

Filters in light polluted skies:

 

What scope(s) do you have? 

 

Tony and Red both make good points. Star brightness is Aperture dependent so with a small scope, the lack of stars can be an issue. 

 

Personally, I have a UHC, O-lll and H-Beta. From my urban backyard I use the O-lll most of the time for the very reasons Red listed. I don't worry about seeing stars. And most often, I'm looking for some object that's I've seen many times from dark skies but is quite difficult from light polluted skies.

 

For enhancement of brighter nebulae, the UHC still increases the contrast by more than 2 Magnitudes and the object may well be brighter than with O-lll so it maybe your filter of choice.

 

Jon

[Redbetter]

Yes, Tony's point about the stars is a good and valid one.  However, if the primary interest is in seeing the nebulosity, then the extra reduction in brightness of stars is a favorable trade.   It becomes more a matter of aesthetic preference or what the primary objective is with the filter. 

 

For planetary nebula the loss of stars is generally inconsequential since the central star is sometimes still visible with the filter, or the filter can be removed to reveal the star.  If one is viewing an emission nebula/cluster then retaining stars while seeing the nebulosity is desirable...but that has some practical limitations.  

 

It isn't like someone is going wrong by picking one of these over the other.  It is more of a balancing act to try to best suit one's own needs and preferences in the short term.  As long as a high quality filter is chosen, nothing is lost if one determines that the need has changed.  Make best use of whatever is chosen, and then add other capabilities later.

[Tony Flanders]

I'm a proponent that if you can afford both, then do it.

I agree 100%. The only question is which one to buy first.

[John Turley]

I'm a proponent that if you can afford both, then do it. I do, in 1.25" and 2" but again, that's just me.

Ideally put them in a filter wheel and leave one port empty, so you can compare the view with different filters, plus with no filter 

[cuzimthedad]

Ideally put them in a filter wheel and leave one port empty, so you can compare the view with different filters, plus with no filter 

I have a filter slide on my new Teeter but haven't had the opportunity to put it to use. Soon though.

[stevew]

What works better for most nebulae in light polluted skies, UHC or OIII filter (Astronomik or Lumicon Gen.3 OIII)?

What size telescope do you have?

If you have an 8 inch or larger the OIII maybe a good choice, if you have a 4 inch or smaller the UHC maybe a better choice.

[tommm]

The scope is 22.4".  I was surprised by havasman's comment that "all good filters work best under dark skies."  I never even thought of using one there.  Will have to try it.  Sometimes the weather is iffy and I don't want to take the risk of driving a couple hours to dark skies, so I'll set up at home under Bortle 5/6 skies (I can only see 3 stars in Ursa Minor). Buying both would be nice but I'm tight.  - at least with hobbies.

 

Maybe I'll go with a UHC and, if we ever have star parties again, try to compare it against someone's OIII.  Thank you all for very helpful comments.

[Tony Flanders]

The scope is 22.4".

Oh, man. If you can afford a 22-inch scope, you really can afford to shell out for more than one good nebula filter!

Filters only work on the objects where they work. But when they work, they often work wonders. The view of the filtered Veil is worth several hundred dollars all on its own.
 

I was surprised by havasman's comment that "all good filters work best under dark skies."

Yes, I think most of us would agree with that statement. Natural background skyglow is really bright, you know!