Which filter?

[John]

My O-III seems to work well from 21x to 265x.

The Owl is a good example of where an O-III will show something thats pretty hard to see without a filter. The interesting thing is though that it's worth trying to pick up without the filter as well because, at low power, it shares a wide field of view with a nice edge on galaxy M108. On a dark night without the filter they make rather a lovely pairing but the O-III filter makes the galaxy disappear from view and the effect is lost.

[LDW1]

Thinking of ordering a uhc or o-iii filter but cant decide which i would get most use of. Will be used mainly with 200p dob and sw 26mm panaview eyepiece.

Most if not all high time amature astronomers recommend the UHC filter before the 0-III as the UHC has a wider band width thus not as restrictive as the 0-III ! The UHC will darken the view while blocking certain colors thus providing excellent views mainly of some types of nebulas, while allowing you to still see adjacent stars more faintly which tends to provide a better contrast as it relates to the overall view ! Nebulas such as Orion, Lagoon , Eagle etc will widen out and become more intense to the point of becoming breath taking from just great on those nights when skies are at their best !! The 0-III is still a great filter but restricts the view / contrast to the point where you will only be focused on the nebula with little or no adjacent detail ! It's your call !

[John]

.... The 0-III is still a great filter but restricts the view / contrast to the point where you will only be focused on the nebula with little or no adjacent detail ! It's your call !

With respect, this is not the case with all O-III filters and will depend on the aperture of the scope thats being used too.

So many variables to consider !

[Moonshane]

Most if not all high time amature astronomers recommend the UHC filter before the 0-III as the UHC has a wider band width thus not as restrictive as the 0-III ! The UHC will darken the view while blocking certain colors thus providing excellent views mainly of some types of nebulas, while allowing you to still see adjacent stars more faintly which tends to provide a better contrast as it relates to the overall view ! Nebulas such as Orion, Lagoon , Eagle etc will widen out and become more intense to the point of becoming breath taking from just great on those nights when skies are at their best !! The 0-III is still a great filter but restricts the view / contrast to the point where you will only be focused on the nebula with little or no adjacent detail ! It's your call !

I don't!

[swamp thing]

Most if not all high time amature astronomers recommend the UHC filter before the 0-III

Really?

Well that's that then

[AlexB67]

There seems to be quite appreciable variety in the transmission curves, hence I assume the varied reports when a is better or more suitable than b, depending which one you are using I get the impression.   In the end of the day it is not a bad idea to own both I feel at some point, a UHC and an OIII.  Reading some lengthy reports from observers with a lot of experience will  say that some do better on some targets in certain situations, and seems to be the common consensus everywhere I read about them in most cases.  

I started with he UHC and have no regrets after using it the first time looking at a few targets the other day in my smaller Dob. it did exactly what I hoped it would do as advertised on the tin  . The filter I have is rather broad, everything is still visible with it on when star hopping even in my 5 inch Dob, that makes it easy to use as a nice starter filter and it is what I wanted, hence I opted for it instead of an OIII as a first filter. Worked great when there was a bit of moon and just darkening that sky background and supressing that bit of LP.  it really enhanced the objects more rather than making visible what isn't there, but that value is not to be underestimated now that I looked through one, because it can bring out features and details that otherwise would be much less obvious, it does that job nicely. 

[Spec-Chum]

Anyone tried looking at m31 through a uhc?

I swear I can see more detail.

Probably just me to be fair...

Sent from my Nexus 4 using Tapatalk

[John]

I tried a Baader UHC-S on M31 quite a while back. I fancied that it did bring out the contrast of the galaxy just a little especially seeming to "harden up" one edge of the core where one of the dust lanes cuts across it. The effect was very subtle at most though. 

[RikM]

I use my UHC a lot more than my OIII because I prefer the (relatively) brighter view. I would rather see a greater extent of faint wispy stuff, than more contrast in the dark stuff. This is what the UHC does very well. I think the OIII would be used more from out of town, when properly dark adapted to be able to take advantage of the higher contrast boost. 

[AlexB67]

Anyone tried looking at m31 through a uhc?

I swear I can see more detail.

Probably just me to be fair...

Sent from my Nexus 4 using Tapatalk

I had to try this too in my smaller 5 inch the other day in fairly light pollute skies I should add, obviously as we are all a bit mad one has to try and see the things that filters are not usually really recommended for :0) In this particular instance the best way I can describe it, it looked different, rather than anything else. I preferred it without, even though the background was darker, so was the whole galaxy and core and spread. It did not add anything to the view  in this particular case for me to say it enhanced anything I would not otherwise be able to see without it.  More like, it took some things away.  Perhaps that it gives rise to the notion of revealing some extra details can be argued, as that is all a filter does, it blocks and  transmits some wavelenghts, but for a galaxy with a wide spread, I can't see it being that effective in that case other than just providing a different view as much as anything.

[bingevader]

Great discussion, enjoying it immensely, as usual!

Cheers

[Joves]

I agree, it is a great discussion. Highlights that there is no black and white, right or wrong in this game. So many variables at play, including a ones own tastes (and eyeballs) to give a definitive answer to a lot of the tougher questions/advice being sought!

In short, I think the correct answer to this one is... Buy them both!!!

[swamp thing]

Personally I find that, the UHC works on more objects, but that is not the end of it. The UHC filter is less aggressive, therefore its contrast is nearly always LOWER. It has nothing to do with stars in the background. It's to do with light blocked. The O-III blocks more light, therefore with any light left the contrast will be higher, that's simple logic. Due to its greater light blocking ability It also seems to work better at lower powers. I find it works best on larger targets like the rosette and NA neb for this reason. The line filters often giving a more dramatic effect at larger exit pupils. As we push power up the UHC seems to help more as the increase in power brings up a darker more contrasty view on its own.

The UHC often shows a wider expanse of nebulosity (specially in objects like M42) but for contrast, structure, and detail the O-III will often edge it.

Some say the UHC works best on M42, I disagree. I say, it works differently. My take is. The UHC offers the fainter outer regions whilst the O-III rules on detail. I find the same is true on the omega, and lagoon nebulae. For more expanse of nebulosity pick the UHC for structure you want an O-III. O-III filters give darker dark areas and for this reason show up dust lanes better, the lagoon is stunning through an O-III filter for this reason. An UHC will show the lagoon nebula as more expansive though.

As one can see It's not an open and shut case by any means. Personal preference pays a huge part in what one likes in a filter.

It's tougher to get proper dark adaption so one can get the most out of an O-III filter, for this reason for urban use I'd pick an UHC filter. For dark skies I'd pick an O-III, but again others will differ.

UHC's filters work, and work very well, there is no question of that, but the O-III can really deliver jaw dropping results on some objects and for that reason alone is my filter of choice.

[jetstream]

Swampthing,very well put,great explanation of filter use and performance.Thanks