Would UHC filter help

[Don Pensack]

UHC-type like NPB--passes H-ß and O-III and is a universal filter for emission nebulae of all kinds.

O-III passes two O-III lines in the spectrum and creates great contrast on objects that emit more energy in O-III than in Hydrogen emission, like supernova remnants, planetary nebulae, Wolf-Rayet Excitation nebulae.

H-ß  passes only the H-ß line and maximally enhances contrast for large, faint hydrogen-only emission nebulae.  Almost all of these objects have very low surface brightnesses, like IC434, the nebula behind the HorseHead (B33).

If you get one, get a narrowband UHC-type.

Examples:

TeleVue BandMate II Nebustar*

Astronomik UHC**

Lumicon Gen.3 UHC**

DGM NPB*

Orion Ultrablock#

Thousand Oaks LP2

and so forth

* transmits no red, stars are blue green

** transmits red as well as blue green Stars have red in them.

#varies in quality, but mostly are good.

My TO wasn't good at all.

Brands to avoid: Explore Scientific, Optolong, StarGuy, Celestron UHC/LPR, Baader UHC-S, Astronomik UHC-E, DGM VHT, or anything with a bandwidth > 30nm.

[John]

12 hours ago, Pixies said:

Thanks @John and @Don Pensack

I was looking at getting a UHC and Oiii. Both 2" - so probably one soonish and then the other later. 2 questions, please:

1. Is the NPB more similar to a UHC? And if so, which is better?

2. I know the Oiii is the one-to-have for the Veil, but is the UHC more general-purpose and perhaps get more use in the long term?

 

Sorry - that looks more like 3 questions!

Cheers

My understanding is that the NBP is a UHC class of filter.

My way of thinking about this is that a UHC enhances things which I can already see so that's a "nice to have". The O-III shows me things well that are practically invisible otherwise so that has been a tool that I have always wanted in my tool box.

There have been periods when an O-III was my only deep sky filter and I've not really missed not having a UHC. The UHC's that I have now don't get used all that much but the O-III's are regularly used and I would really not want to be without one. I know what I'd be missing

Knowing what I do now, the O-III would always be a higher priority for me than a UHC I I found myself with no deep sky filters.

That's my findings over the years given my observing preferences, scopes and skies. Yours and others may well be different though

 

 

[Louis D]

16 hours ago, Pixies said:

2. I know the Oiii is the one-to-have for the Veil, but is the UHC more general-purpose and perhaps get more use in the long term?

In 20+ years of observing and having both Lumicon UHC and OIII filters, I find I rarely use the UHC.  Adding H-ß to the O-III lines just does not overcome the loss of contrast due to the wider passband.

[Don Pensack]

The view of M8, M20, M17, M16, M42 are all better with a UHC than an O-III.

That's because these nebulae pass a LOT of hydrogen AND oxygen light.

Using either an H-ß or an O-III filter on these large H-II gas clouds merely reduces their sizes and darkens them appreciably.

On O-III targets, the narrower bandpass of the O-III filter helps improve contrast a lot.

[John]

17 minutes ago, Don Pensack said:

The view of M8, M20, M17, M16, M42 are all better with a UHC than an O-III...

 

Agreed, but most of those are also visible and rather nice without a filter.

 

[Louis D]

29 minutes ago, Don Pensack said:

The view of M8, M20, M17, M16, M42 are all better with a UHC than an O-III.

That's because these nebulae pass a LOT of hydrogen AND oxygen light.

Using either an H-ß or an O-III filter on these large H-II gas clouds merely reduces their sizes and darkens them appreciably.

On O-III targets, the narrower bandpass of the O-III filter helps improve contrast a lot.

It also depends on how savage the light pollution is that they're embedded in.  I'll have to try them out at a dark sky site someday to see if indeed the UHC performs better than the OIII under those conditions.

Perhaps if ordinary UHC filters were more like the OPT Triad Quad-Band Ultra filter with the intermediate wavelengths excluded, it would be more usable in light polluted skies:

	Hydrogen-beta	Oxygen III	Hydrogen-alpha	Sulfur II
FWHM	5 nm	4 nm	4 nm	4 nm
Peak Transmission	79%	97%	87%	90%

[globular]

The DGM NPB:

looks, to my eye, to get closer to the OPT than the Astronomic UHC:

 

 

Edited October 2, 2020 by globular

[jetstream]

We must all be aware of nominal specs- IMHO.

[Don Pensack]

If maximum contrast is desired in a narrowband UHC-type filter, the obvious candidates are the TeleVue Bandmate-II Nebustar (26nm bandwidth, zero red transmission)

or the Lumicon UHC (27nm bandwidth, zero red transmission).  If observing in severe light pollution the H-II nebulae, removing red might help.

My sample of the DGM NPB had a 21nm bandwidth in the blue green, but had the same two peak orange and red transmission shown in post by Globular (BTW, the two peaks correspond to

no wavelength of emission for the shorter wavelength, and H-α for the longer wavelength peak, so no homologue to the photographic filter mentioned by Louis. The OPT Triad is not a visual filter and only picks up the 500.7nm O-III line).

Gerry's point about nominal specs is apropos--filters vary a bit from one sample to the next.  Doveryai no proveryai, trust, but verify.