UHC vs. O-III Filter?

[LanaB]

I currently have an ultra high contrast filter - Zhumell High Performance UHC - and have had some luck seeing additional features in larger objects while using it.  I was thinking about purchasing an Oxygen-III filter also, but wonder just how different is the O-III compared to the UHC?  Is it worth the money to have both in my filter collection?

My scope is only a 130mm, and I would love to see additional details while finding and viewing DSOs such as Dumbbell and Ring nebulae, see more details in Eagle, Trifid, etc.  It would be awesome to find something that would also enhance galaxies too (M31, M33 etc.).

Does anyone know if an O-III filter will perform better than my current UHC filter?

[John]

Hello and welcome to the forum

An UHC filter is a bit more versatile but an O-III has more impact on contrast on those objects that it majors on. The effect of the O-III filter is really impressive on objects such as the Veil and Owl nebulae.

Personally I find having both types very useful.

Here is a link to the well known piece by David Knisely on filters and their effects:

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

Well worth a read and from my experience, pretty accurate.

I've used O-III filters in scopes with apertures as small as 80mm so the old myth of needing 8" or more of aperture does not really hold true in practice I'd say.

No filter enhances galaxies as far as I'm aware. O-III and UHC filters tend to dim them so have the opposite to the desirable effect. As one person once said on a forum, the best accessory to improve the view of galaxies is to put some gas in your fuel tank and get yourself and your scope to a darker site. They were correct !

 

[alanjgreen]

Wot John just said above

All I would add is that "you get what you pay for" when it comes to filters. The expensive ones are expensive for a reason.

post up which manufacturers you are considering and we can tell you which of them is highest rated.

[ronin]

A UHC filter "should" (I believe) pass the OIII band and the Ha band, while blocking the chunk inbetween. Some UHC filters when you examine the actual filter curves are just OIII. The Lumicon falls into this situation, as it passes the OIII but no Ha. So in their case may as well buy the OIII as they are effectively the same.

Problem is that I cannot locate anything the supplies the fliter curve for the Zhumell UHC filter. If you have a filter transmission curve supplied then see if both OIII and Ha are passed by the filter.

But as said already no filter adds to the spectrum, they all subtract, the fine point is know what you want extracted and therefore what is left.

[LanaB]

Thanks to you both!  And thanks for the link to the filter article, I have it pulled up now.

I have noticed M31 does look best naked-eye rather than through any of my filters, was curious if O-III helps with those as well.

I am a bit of a cheapskate and am trying to keep the cost below my fairly small bonus money (LOL), was looking at the Zhumell HP O-III filter or the Celestron O-III Narrowband filter.  The Celestron sounds like a better filter from what I've read, but I'm not sure. 

Thanks so much for the help!

[LanaB]

Thanks Ronin!  The UHC I received just came as the filter itself, no documentation with it.  I may have to google it and see if Zhumell may be has those specifications on their own website, thanks for the tip!

 

[swamp thing]

2 hours ago, ronin said:

A UHC filter "should" (I believe) pass the OIII band and the Ha band, while blocking the chunk inbetween. Some UHC filters when you examine the actual filter curves are just OIII. The Lumicon falls into this situation, as it passes the OIII but no Ha. So in their case may as well buy the OIII as they are effectively the same.

 

I think you are confusing Ha for the much more useful H-Beta line which the lumicon UHC allows to pass.  

BTW it was Lumicon that first used the term UHC to describe their narrow band filter. So their narrow band filter is actually the definitive UHC filter  

[jetstream]

Filters... I bought a mid range filter (Ultrablock) which was no good and this turned me off UHC type filters... until I bought a Lumicon UHC, which is excellent as is my Lumicon OIII.

BUT WAIT

My Lumicon Hb seems to be under performing and is being tested shortly.

There is a point here (somewhere lol!), there are good copies, mediocre copies and poor copies even within expensive brands IMHO. The only brand (to me, so far) that has shown consistently good performance is Astronomik - I own the OIII and an excellent 1.25" Hb. I have heard that they tightened their bandpasses a bit which is nice and that they test filters individually now.

While nothing beats dark skies, a good OIII might shock you with the views on certain objects like the Veil nebula. Just my thoughts...

[Moonshane]

Ignoring Individual variances In band pass or quality (you'll never buy all the options and compare them after all) my view is that:

 -uhc filters enhance slightly what you can already see

- Oiii and (in theory anyway) Hb filters allow you to see things otherwise invisible

I have budget Castell and Skywatcher filters and have always been happy although I have long term plans to upgrade to Astronomik eventually.

[LukeSkywatcher]

Both for me. 

[Stu]

16 hours ago, LanaB said:

I currently have an ultra high contrast filter - Zhumell High Performance UHC - and have had some luck seeing additional features in larger objects while using it.  I was thinking about purchasing an Oxygen-III filter also, but wonder just how different is the O-III compared to the UHC?  Is it worth the money to have both in my filter collection?

My scope is only a 130mm, and I would love to see additional details while finding and viewing DSOs such as Dumbbell and Ring nebulae, see more details in Eagle, Trifid, etc.  It would be awesome to find something that would also enhance galaxies too (M31, M33 etc.).

Does anyone know if an O-III filter will perform better than my current UHC filter?

With apologies if any of this is stating the obvious....

Choosing a filter is about understanding what you are trying to see....... more specifically it is about which frequencies of light the object possesses which you want to enhance.

Filters remove light which is not useful to you i.e. is not coming from the target object you are viewing, but they always reduce the total light available. It has been said that an OIII is no good on scopes less than 8". I disagree with this having used then in scopes down to 80mm and under dark skies they definitely help perceive specific objects more clearly.

Galaxies are faint, but emit light across the spectrum. As John rightly says, using a filter on them generally just reduces the amount of light reaching your eye so makes them appear dimmer. One possible exception to this is viewing Ha regions in galaxies like M33 where a Deep Sky filter which passes Ha frequencies would help bring out these features whilst dimming the rest of the Galaxy.

Objects like M42 are complex in that they are both reflection and emission nebulae. Reflected light is across the spectrum whilst emitted light will likely be in the OIII or Hb frequencies. In this instance using either an OIII or a UHC might be useful but would show different views. The OIII tends to give better contrast in the central regions, whilst dimming or removing the more subtle outer areas. The UHC does the opposite, less contrast but better visibility in the outer areas, the object may look physically bigger.

As a VERY rough guide:

Deep Sky filter passes Ha, Hb and OIII

UHC passes Hb and OIII

OIII passes.... yep, OIII

When Shane says an OIII can make invisible objects visible he is totally right. The Veil Nebula, which is a strong OIII emmision Nebula is totally invisible at my light polluted home site, but does become faintly visible using the OIII because it cuts out all the LP and allows the Nebula to show i.e. It lowers the total brightness but increases the contrast between sky background and the object to the point which allows it to be seen. You still need to be as well dark adapted as you can be, but the filter helps.

Some useful resources below. The first is, I think, very useful for understanding the frequency responses of the filters and the other links are comprehensive reviews or guides to which filter do what best.

Stu

http://www.astrosurf.com/buil/filters/curves.htm#Lumicon UHC

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

http://www.prairieastronomyclub.org/useful-filters-for-viewing-deep-sky-objects/

[Moonshane]

Think of filters as like a parent pengin's ears. It cannot possibly hear its chick if it listens to the cacophony of the rookery but it is tuned in to the frequency and specific song of its progeny making it stand out against the background noise.

[Stu]

19 minutes ago, Moonshane said:

Think of filters as like a parent pengin's ears. It cannot possibly hear its chick if it listens to the cacophony of the rookery but it is tuned in to the frequency and specific song of its progeny making it stand out against the background noise.

Surreal, but very helpful  

[niallk]

I like the penguin analogy

I too have both O-III and UHC (Astronomiks).  I find they both have their place, and I'd recommend the O-III as a first purchase, then maybe save up for a UHC ... for the reasons well covered in the posts above.  I was so impressed, I then saved up for a cheap filter wheel which is brilliant in my 250px for swapping at a flick between no filter/O-III/UHC/Neutral Density/Green No pulling out the EP and screwing on, then finding you've disturbed the scope and lost your target and having to unscrew to go back searching... 

[Dave In Vermont]

For visual applications of the OIII, I agree with Gerry above in his recommendation of the Astronomik. They have the best bandwidth of light to get the most out of these. I had a Baader OIII, but I retired it after trying the Astronomik. Cost-wise they are all about the same, but I would still go for this even if the cost was higher still. Why throw my money for 2nd. best?

A bargain in terms of filters are quite rare. "You get what you pay for" is the general rule here.

Have fun!

Dave - the Filter-Nut

[Moonshane]

The worrying thing is that the penguin analogy came straight out of my head in one, off the cuff

[Stu]

I don't know Shane, waddle you think of next?

[Moonshane]

Ule Have to C

 

[Louis D]

On 1/3/2017 at 11:19, LanaB said:

I currently have an ultra high contrast filter - Zhumell High Performance UHC - and have had some luck seeing additional features in larger objects while using it.  I was thinking about purchasing an Oxygen-III filter also, but wonder just how different is the O-III compared to the UHC?  Is it worth the money to have both in my filter collection?

I have both the Lumicon UHC and OIII filters, and the latter does make certain nebula like the Veil stand out much better than with the former.  I find I use the OIII more than the UHC because when I am going to the trouble to screw in a filter, I want the maximum contrast boost possible.

I also picked up a Zhumell OIII for cheap to see how it compares.  It doesn't really compare.  It does restrict the range of light, but it doesn't seem very precise or do that great of a job of darkening the background sky like the Lumicon OIII.  Even just looking at them, it's obvious they're quite different.  The Lumicon looks like a mirror, the Zhumell looks like a an oddly colored green filter.  I highly recommend you save up for one of the top end brands when it comes to OIII filters.  Precision manufacturing and quality control really do matter when you're talking about very narrow band filters.

On the other hand, their Urban Sky Filter works very well to cut sky glow without introducing lots of weird colors to passed light.  I was able to pick out a comet lost in the sky glow murk above the city to my west using it.  It was completely invisible without it.  It's also quite useful as a contrast enhancing filter on Jupiter.  It's sort of like looking at Jupiter through a binoviewer with red/blue 3D glasses, but with a single eye.  You can't stare for very long because you'll get eye strain while your brain is trying to sort out what's going on.

[LanaB]

Wow, this is my first post and I'm already glad I found this group!  Thanks so much for everyone's input!

After reading all of the feedback, and especially Louis' last comment regarding an Urban Sky Filter, maybe that's my better choice?  I have somewhat polluted skies (south of Atlanta) and am looking for something that gives me better views of the targets I normally have a hard time finding and seeing well.  I've read good things about the O-III filters and thought that might be my next best buy, but maybe an Urban filter would be more practical?  Or even a better UHC than I have now, maybe the Baader UHC-S Nebula filter?

https://www.telescopesplus.com/collections/telescope-accessories/products/baader-planetarium-uhc-s-nebula-telescope-filter

Penguin ears... that one got me!!  Good analogy though!

[alanjgreen]

When I lived in the town, I used a Baader Neodymium filter (see if you can spell that!), it was great for cutting out the glow from the street lights and the moonglow.

https://www.firstlightoptics.com/light-pollution-reduction/baader-neodymium-filter.html

It was also useful on the moon (used as a moon filter it reduces the brightness of the moon very slightly but enough to allow you to stay at the eyepiece for longer) and it was also great on Mars & Jupiter (brought out more colors on the planet surface!)

 

Did we conclude the Zhumell UHC was a good one? If we didn't then I would still consider getting a "good" UHC if it is the nebulas that you are interested in.

Lana - I have never  used a Baader UHC-S but I am sure I read somewhere that it is not a "UHC" but some sort of hybrid - others can confirm or deny ?

I can recommend the astronomik UHC - expensive but very very good

 

[Louis D]

3 hours ago, LanaB said:

Urban Sky Filter, maybe that's my better choice?

I checked Telescopes Plus (used to be part of Hayneedle), and they now have the 2" version priced at $22.  When I signed up, I got a $10 credit, possibly from the last time I ordered from them back when they were part of Hayneedle.  With shipping, I got it for $16!  I plan to put it on the front threads of my refractor's diagonal when scanning my western skies.  The 1.25" is sold out, unfortunately.  Even for $26 shipped, how wrong can you go?

[John]

The Baader UHC-S was my 1st narrowband filter. It worked well enough with the small scopes that I had then but I've now realised that a full blown UHC or O-III would have been a better bet.