Do I need a UHC?

[Kon]

I have an 8" Dob and my interest is observing nebulas. My skies are fairly dark, bortle 3, or as in previous discussions I can see the Milky Way bright and with structure. I have a Televue bandmate type 2 OIII filter and it has been great on several nebulas, although I seem to prefer unfiltered views. My question is, do I need a UHC filter and will it give me an advantage over the OIII?

I have seen this excellent site on performance but I am not sure under what skies.

https://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/

If yes, I am after a good quality filter and I have seen good reports on the following. Which one would you recommend or have I missed any others? My lowest magnification EP is the ES 24mm 68degrees if that matters.

Lumicon UHC

DGM NPB

Astronomik UHC

Explore Scientific UHC

TeleVue BandMate Nebustar

[scarp15]

Yes, including a high spec UHC type, for enhanced resolving of certain nebulae subject, will be an advantage and will be complementary to your O-III, not jostling in competition. Each of my filters are 2" older type Lumicon of excellent spec. Purchasing now, perhaps I would be persuaded by the TeleVue Nebustar. 

[globular]

UHC is not better or worse than OIII - they each work well on different target types.  Having both in your bag is better than just one. 

I'm the same as you in that no filter is my preference most of the time.... but when the skies are dark and the exit pupil is large they really come to life and help bring out features not seen without them.

I like my DGM NPB very much.

[IB20]

I have one but rarely use it but I’m in bortle 6-7. I think if you could pick up a cheaper 2nd hand one, in bortle 3 it could probably be quite a useful addition.

[Kon]

10 hours ago, scarp15 said:

Yes, including a high spec UHC type, for enhanced resolving of certain nebulae subject, will be an advantage and will be complementary to your O-III, not jostling in competition. Each of my filters are 2" older type Lumicon of excellent spec. Purchasing now, perhaps I would be persuaded by the TeleVue Nebustar. 

I agree that it will have its own uses, which sort of answers my question. By the way, why the Nebustar over the Lumicon?

[Jiggy 67]

Personally I prefer the uhc over the OIII. Its not just about the darkness of the sky but also the aperture of the scope. I also use an 8inch newt and find it's at the limit of usefulness for an OIII filter, it's just about enough for this filter but I definitely wouldn't bother with a smaller aperture because an OIII will just darken the image too much, you need as much light as possible with this filter which is why it is not the best for an 8inch. I find the UHC better as it has a wider bandpass. I love observing planetary nebula, many of them can be seen without a filter, a UHC will assist in making it stand out against a black background, some, even in light polluted skies. The same object disappears from view with an OIII...when it would look great with a 12inch scope. I use the Astronomik filter (all my filters are Astronomik or Baader) and can fully recommend it.

[scarp15]

14 hours ago, Kon said:

I agree that it will have its own uses, which sort of answers my question. By the way, why the Nebustar over the Lumicon?

Quite subjective, Lumicon have been through a lengthy transition period, from their former high esteem, although I understand that their existing product line (some filters are no longer in production) is of high standard once more. The Nebustar has received consistent good reviews by respected users on here. 

The nice thing about having both filters to hand, is when revisiting particular subjects, simply making comparisons, each may tease out certain characteristics. Probably like you, I only use these filters within dark sky locations, when dark adapted etc. Aperture is then less relevant, I have used these filters successfully on subjects with 76mm right up to 350mm. 

[Zeta Reticulan]

TBH I can use a narrowband OIII with my SW 80ED DS Pro. Admittedly I need an exit pupil of at least 5mm and I live in the greenbelt, but it can be done. 

[Louis D]

4 hours ago, Jiggy 67 said:

Personally I prefer the uhc over the OIII. Its not just about the darkness of the sky but also the aperture of the scope. I also use an 8inch newt and find it's at the limit of usefulness for an OIII filter, it's just about enough for this filter but I definitely wouldn't bother with a smaller aperture because an OIII will just darken the image too much, you need as much light as possible with this filter which is why it is not the best for an 8inch. I find the UHC better as it has a wider bandpass. I love observing planetary nebula, many of them can be seen without a filter, a UHC will assist in making it stand out against a black background, some, even in light polluted skies. The same object disappears from view with an OIII...when it would look great with a 12inch scope. I use the Astronomik filter (all my filters are Astronomik or Baader) and can fully recommend it.

At what exit pupil(s) are you observing?  I've used my 1990s Lumicon OIII down to 2mm EP on brighter nebula to good effect in my 8" Dob.  Yes the view dims, but if you study the image for a few minutes, fine edge details will tend to pop out that weren't obvious without it.  It's also indispensable to reveal the Veil nebula under Bortle 5 skies.

[Zeta Reticulan]

David Knisely has written a lot on filters. 

[Louis D]

8 hours ago, Zeta Reticulan said:

David Knisely has written a lot on filters. 

In case you missed it, the OP led off with a link to that page.

[Zeta Reticulan]

23 minutes ago, Louis D said:

In case you missed it, the OP led off with a link to that page.

Thanks Louis. LOL ... my ADHD strikes again! Ooh look ... shiny! Normal service will resume as soon as possible ... ROTFL.

I bought this GSO 42mm SuperView a year or so ago specifically to observe nebulae in the Summer Triangle. The idea is that I compare my Baader OIII (narrowband) and ES OIII (broadband) filters with it in my 80 ED DS Pro. I've never actually used it.  I keep forgetting I bought it. I'm getting worse ...lol.

Edited July 30, 2022 by Zeta Reticulan

[Kon]

@Louis D and @scarp15 I agree that my OIII is giving me great views in my 8" Dob. I will look into the Nebustar.

@Jiggy 67 I have no issues with my OIII and most of the time if transparency is bad then there is not much benefit. I have fairly good skies and even Veil can be observed without a filter but it pops better with one. The Astronomik allows some red through, does that make much of a difference compared to a narrow band UHC?

[Don Pensack]

On 28/07/2022 at 14:14, Kon said:

I have an 8" Dob and my interest is observing nebulas. My skies are fairly dark, bortle 3, or as in previous discussions I can see the Milky Way bright and with structure. I have a Televue bandmate type 2 OIII filter and it has been great on several nebulas, although I seem to prefer unfiltered views. My question is, do I need a UHC filter and will it give me an advantage over the OIII?

I have seen this excellent site on performance but I am not sure under what skies.

https://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/

If yes, I am after a good quality filter and I have seen good reports on the following. Which one would you recommend or have I missed any others? My lowest magnification EP is the ES 24mm 68degrees if that matters.

Lumicon UHC

DGM NPB

Astronomik UHC

Explore Scientific UHC

TeleVue BandMate Nebustar

Yes, you need a narrowband UHC-type for nebulae with substantial H emission.

The Lumicon Gen.3 UHC is excellent--rating A  Ones from 2005-2011 are also excellent.  Avoid any from before 2005.

The DGM NPB has a slightly lower transmission, but also a slightly narrower bandwidth.  It also passes red wavelengths, making stars appear red.  On the nebulae, though, rating A+

The Astronomik UHC is excellent, also passing red, though stars are not as red as in the DGM.  Similar to Lumicon in enhancement.  Rating A  Ones made before 2016 are too wide--avoid.

The Explore Scientific UHC is very broad and closer to the bandwidth of a broadband.  As a UHC-type filter, rating D (not F, because there is a very slight enhancement)

The TeleVue BandMate II Nebustar has no red transmission so is very close to the Lumicon--Rating A.  Earlier Bandmate I would be rated C- on the same scale, so do not buy a used one.

My favorite of the bunch is the DGM, since you already have a good O-III.  It will be the most different in performance from your O-iii on the larger H-II gas cloud nebulae.

[Don Pensack]

20 hours ago, Jiggy 67 said:

Personally I prefer the uhc over the OIII. Its not just about the darkness of the sky but also the aperture of the scope. I also use an 8inch newt and find it's at the limit of usefulness for an OIII filter, it's just about enough for this filter but I definitely wouldn't bother with a smaller aperture because an OIII will just darken the image too much, you need as much light as possible with this filter which is why it is not the best for an 8inch. I find the UHC better as it has a wider bandpass. I love observing planetary nebula, many of them can be seen without a filter, a UHC will assist in making it stand out against a black background, some, even in light polluted skies. The same object disappears from view with an OIII...when it would look great with a 12inch scope. I use the Astronomik filter (all my filters are Astronomik or Baader) and can fully recommend it.

Remember that large exit pupils work best with filters--2.5mm or larger (i.e. magnifications under 10x/inch).

I also like planetary nebulae, but most look best at high powers, where filters are ineffective.

If a planetary disappears with an O-III, then it is not a good O-III object, and has a lot of H emission.  Example: M27, better with a narrowband than an O-III line filter.

[Louis D]

4 hours ago, Zeta Reticulan said:

4 hours ago, Zeta Reticulan said:

my ADHD strikes again! Ooh look ... shiny!

I've never actually used it.  I keep forgetting I bought it. I'm getting worse ...lol.

Squirrel!!!!

[Louis D]

2 hours ago, Kon said:

The Astronomik allows some red through, does that make much of a difference compared to a narrow band UHC?

If your eye is sensitive to far red, it can be useful to pick up Hα emissions.  However, based on my experience with my 1990s Lumicon UHC filter, bright stars are both blue-green and red at the same time, so they are incredibly weird looking and difficult to focus simultaneously onto your retina:

The improved DGM NPB looks the part below:

You should be able to pick up all of the useful emission bands except for the C2 Swan bands (mainly from comets).

[Kon]

1 hour ago, Don Pensack said:

Yes, you need a narrowband UHC-type for nebulae with substantial H emission.

The Lumicon Gen.3 UHC is excellent--rating A  Ones from 2005-2011 are also excellent.  Avoid any from before 2005.

The DGM NPB has a slightly lower transmission, but also a slightly narrower bandwidth.  It also passes red wavelengths, making stars appear red.  On the nebulae, though, rating A+

The Astronomik UHC is excellent, also passing red, though stars are not as red as in the DGM.  Similar to Lumicon in enhancement.  Rating A  Ones made before 2016 are too wide--avoid.

The Explore Scientific UHC is very broad and closer to the bandwidth of a broadband.  As a UHC-type filter, rating D (not F, because there is a very slight enhancement)

The TeleVue BandMate II Nebustar has no red transmission so is very close to the Lumicon--Rating A.  Earlier Bandmate I would be rated C- on the same scale, so do not buy a used one.

My favorite of the bunch is the DGM, since you already have a good O-III.  It will be the most different in performance from your O-iii on the larger H-II gas cloud nebulae.

Thank you very much for the rankings and excellent explanation on the different filters. It seems that I will have to source a  DGM.

[Kon]

12 minutes ago, Louis D said:

If your eye is sensitive to far red, it can be useful to pick up Hα emissions.  However, based on my experience with my 1990s Lumicon UHC filter, bright stars are both blue-green and red at the same time, so they are incredibly weird looking and difficult to focus simultaneously onto your retina:

The improved DGM NPB looks the part below:

You should be able to pick up all of the useful emission bands except for the C2 Swan bands (mainly from comets).

Thanks Louis for the emission lines, they are very useful. I assume i need to source the 'Improved DGM NPB'.

By the way, the other image is tripping my eyes 🤪 but I only see blue and red lines. Is that a good think?

[Louis D]

16 minutes ago, Kon said:

By the way, the other image is tripping my eyes 🤪 but I only see blue and red lines. Is that a good think?

That's right, but imagine seeing red and blue/green star images stacked on top of each other.  They don't blend to magenta, or any other color, to my eye.  It doesn't hurt like the stripes image, but the effect still "trips out" your eyes.  Sometimes, you can't avoid bright stars in nebula because bright nebula often contain young open star clusters.

The eye tripping out is because the human eye can't perfectly focus the far ends of the visible spectrum simultaneously on the retina as exaggerated below:

Edited July 30, 2022 by Louis D

[Don Pensack]

2 hours ago, Kon said:

Thanks Louis for the emission lines, they are very useful. I assume i need to source the 'Improved DGM NPB'.

By the way, the other image is tripping my eyes 🤪 but I only see blue and red lines. Is that a good think?

My DGM must have been an original because it has the triple looped red-orange-to-red response.  Stars appear basically red as the 21nm bandwidth in the blue green is insufficient to add a blue green coloration.

I didn't know they had changed the spectral response of the filter.  The narrow Blue-green and the single peak at H-α will not color stars red--they should appear blue green since the eye's H-α response is well below 1% at night.

DGM still shows the triple loop response on their website:

http://www.npbfilters.com/spectral.html

and the NPB filters tested here:

https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8#

all have the triple loop response.

Here is the spectral curve provided by the filter coater:

https://www.omegafilters.com/product/4384

So I have to ask, where did the "Improved DGM NPB" curve come from?

[IB20]

Don or Louis, no idea if either of you can answer this but I read a few things about UHC filters being good to split Antares. Upon trying (Astronomik UHC) I got a magenta point of light star with a large blue-green “shadow”, it almost certainly wasn’t its companion due to the size, so any idea what it was?

[globular]

2 hours ago, Don Pensack said:

So I have to ask, where did the "Improved DGM NPB" curve come from?

https://www.cloudynights.com/topic/752053-omega-npb-versus-dgm-npb-whats-the-difference/

https://www.researchgate.net/publication/344786145_Omega_Optical_Improved_NPB_DGM_Filter

https://stargazerslounge.com/topic/173662-lumicon-uhc-vs-dgm-npb-filter/?do=findComment&comment=2943504

My reading of this is that DGM came up with their filter spec in the 1990s and asked Omega Optics to make it for them.
For a while (2015-16 or so) Omega tried to sell their own ‘improved’ version - using a very cheeky name and no doubt annoying DGM and their distributors. (or perhaps more likely someone was ripping off both DGM and Omega?)
They now seem to be back in line - still making the one and only and original DGM NPB for DGM; and their own NPB that is now to a very different specification of their own.

Whether you can find any of the ‘improved’ ones on the used market; and whether they really are any better; is debatable.

Edited July 30, 2022 by globular

[Don Pensack]

Thanks for the clarification.

I guess I never saw the "improved" version of the filter.

I'm not all that sure the red transmission is what has the effect in making the filter a good one.

My Lumicon, TeleVue, and Astronomik are all 26-27nm bandwidths, while my DGM is only 21nm in the blue green.  That is a substantial difference in bandwidth.

It may simply be the narrower bandwidth that yields the high performance level, though red coloration in M42, M8, and M17 are a lot easier in the DGM.

I have a 2010 Lumicon UHC with a 22nm bandwidth and no red transmission at all.  I should compare the two more extensively.

[Kon]

On 31/07/2022 at 20:19, Don Pensack said:

Thanks for the clarification.

I guess I never saw the "improved" version of the filter.

I'm not all that sure the red transmission is what has the effect in making the filter a good one.

My Lumicon, TeleVue, and Astronomik are all 26-27nm bandwidths, while my DGM is only 21nm in the blue green.  That is a substantial difference in bandwidth.

It may simply be the narrower bandwidth that yields the high performance level, though red coloration in M42, M8, and M17 are a lot easier in the DGM.

I have a 2010 Lumicon UHC with a 22nm bandwidth and no red transmission at all.  I should compare the two more extensively.

You have me intrigued on colour on M42, 8 and 17 with a UHC. I have seen deep reds and teal green on M42 without a filter (under excellent transparency) but not on the others. Does a UHC routinely help or does  it make them pop more under excellent conditions?

I will be placing an order on the original DGM.