What to expect from UHC and OIII filters

[Star Struck]

A couple of years ago I bought a Lumicon UHC filter and a Lumicon OIII filter second hand. They are both 1.25 inch filters.

I tried using them last night on the Orion Nebula, screwed onto the bottom of a Delos 14mm eyepiece, in a SkyWatcher Equinox 120ED scope from a semi-suburban garden.

I was not particularly impreesed with what I saw. I did not know what to expect, but it made the stars go green and did not make the nebula look any more defined. In fact the view was better without them.

What should I have expected the view to look like?

Did my scope not have enough aperture to be effective? Would it be better in my 8 inch Dob?

 

Tony

[fwm891]

I have the same filters (although not the eyepiece) but in my 10" dob I find very few objects actually look any better. There are two types of filter one visual the other for CCD. The visual have a wider band pass than the CCD filters giving a brighter view.

Not tried them through my 115 APO.

[domstar]

That sounds like my experience with an Explore Scientific UHC and my SW100ed. The difference is very subtle. I've used it on the Orion Nebula once and it was different but not better than without a filter (I would describe it as more solid). There wasn't much difference on the Ring Nebula but after a little time at the eyepiece I could definitely see a clearer ring shape. There's no definite wow moment but with the Swan, Lagoon and others there is a little bit more detail to see. It's an improvement but a slight improvement.

And then came the Veil. Worth the price alone.

I don't have a large aperture or a high end filter and I don't like green stars but it's another tool and I'm coming round to the opinion that most improvements in our hobby are pretty subtle but get appreciated with time. I wonder how much better the Orion Nebular can actually get. It's amazing in my 70mm Lidl scope.

But the Veil is a different matter.

[Cosmic Geoff]

120mm aperture is probably a bit small for use with these filters.   Green stars is an inevitable result of using a filter that only passes a small part of the spectrum.

I have the Baader OIII 10nm visual filter, and found that with my C8 it made a notable improvement on selected objects including M27 and M42. Enough to make me feel that it was worth the investment in the filter.

[Owmuchonomy]

I used my Astronomik 1.25" UHC filter on my ES 20mm 82' EP last night.  The views of M1 and M42 are definitely better with than without.  M42 showed up the dark finger much better and the dual layer of the nebulosity normally confined to images was apparent.  M1 turns into a globular structure rather than a fuzzy blob.  I was using my SW ED150 and the views of M42 are nothing short of spectacular through that.  I also have a 2" Baader OIII filter.  That tends to work best on The Veil.  I guess it depends upon your expectation.  Once I realised that I was bound to get a 'darker' FOV but with increased contrast then my brain could work more stuff out.

[Geoff Barnes]

I have used an Astronomik UHC filter tonight on the Orion Nebula and I have to say the improvement in contrast was quite subtle, a slight improvement but not at all a "wow" factor, I find the unfiltered view perfectly impressive. However, when I used it on the Carina Nebula (I'm in Melbourne), the improvement was quite dramatic, the dark rivers through the gas clouds were much more defined, much blacker.

I also have a recently purchased Optolong H-Beta filter which I have been using to seek out the Horsehead Nebula. I don't think I saw it tonight but I'm really not sure, a couple of times I thought I saw a darker area but it may have been my imagination, I knew it was there, so my brain may well have tricked me into thinking I could see it. I'll keep trying, but I really need darker skies.

It does seem that an O111 filter does make a dramatic difference to the Veil Nebula and I think that will be my next purchase.

 

[Ricochet]

You need to pay attention to the exit pupil when using nebula filters. A 14mm eyepiece in a f7.5 scope gives an exit pupil of 1.87mm. Unfiltered, a 2mm exit pupil is considered ideal so that combination works. However, with a UHC filter you might need to drop down to say 2.5-3mm and with an OIII perhaps 3-4mm. Try the filters with different eyepieces and see what happens. Alternatively, try them with the 14mm and your (f6?) dob, and the additional exit pupil (and magnification) might change things. 

[Moonshane]

I do find the UHC works well on the Orion Nebula more than most objects. Oiii filters are necessary to even see certain objects like the Veil for example. Stick with them and I am sure you'll appreciate them more the more you use them. That said, if you ever decide to sell the Lumicon UHC do let me know!

[JOC]

1 hour ago, Star Struck said:

A couple of years ago I bought a Lumicon UHC filter and a Lumicon OIII filter second hand. They are both 1.25 inch filters.

I tried using them last night on the Orion Nebula, screwed onto the bottom of a Delos 14mm eyepiece, in a SkyWatcher Equinox 120ED scope from a semi-suburban garden.

I was not particularly impreesed with what I saw. I did not know what to expect, but it made the stars go green and did not make the nebula look any more defined. In fact the view was better without them.

What should I have expected the view to look like?

Did my scope not have enough aperture to be effective? Would it be better in my 8 inch Dob?

As the owner of an, afore mentioned 8" inch Dob, I wouldn't hold your breath.  I have a Sky watcher UHC, a Skywatcher Light Pollution, an Optics O-III and an Explore Scientific H-Beta and have tried all these on various objects including the Orion nebula, my outcome was the same as yours, a growing realisation that view was probably better without them.  I am keeping them though in the hope of finding the objects that they make an appreciable difference too, but I even went searching for the Veil with the 'right' filter on one night and still couldn't find it.  I therefore tend to think that Filters might fall into the 'Magic snake oil' side of astronomy equipment.

[Whistlin Bob]

I do wonder how much this is about aperture and the ability to 'push' light through a relatively narrow bandpass. I have an 8" and 14" dob. In the 8" the change is marginal at best, but in the 14" it makes quite a difference. The texture and contrast on M42 is amazing in oiii on the 14", but it also loses some bits of the structure. And as others have said, it transforms the veil.

[Kronos831]

So in your guys's opinion ,are they worth it? Is any filter good for dsos?

 

[jetstream]

3 hours ago, Star Struck said:

screwed onto the bottom of a Delos 14mm eyepiece, in a SkyWatcher Equinox 120ED scope from a semi-suburban garden.

My filters don't work well with this fl eyepiece in the 120ED, the filters do work very well with lower fl eyepieces, such as the 30 ES 82, 32mm TV plossl and the 42mm LVW. Filters work well in most any aperture, using proper eye illumination, IMHO.

[John]

I prefer no filters on most deep sky objects. Generally it's the O-III that gets put into use on the targets where it makes a lot of difference. M42 is not really one of those.

 

[Doc]

Only time I use a filter is to view the Veil nebula. I find the O111 really good for this object.

[Paul73]

I have the same two filters. It would be fair  to say that they improve contrast which doesn’t necessarily equate to revealing vast, hither to unseen swaths of nebulocity (except for the Veil).

Naked, is my preferred observing style (with regard to filters). But some targets respond better than others.

Paul

[John]

An O-III works wonders on the Owl Nebula (M 97) as well

 

[jetstream]

and (OIII) Rosette, Monkey head, Pacman, Lobster Claw, Eskimo, Bubble, Flaming Star, Swan and many more...

Filters work, at least good filters work- my recommended Orion Ultrablock was a piece of junk, now disposed of in the garbage.

[Ags]

I really don't like green stars and can't see a difference in the nebulae, so my UHC gathers dust.

[JOC]

This is actually a hugely reassuring thread.  I thought that it might just be something wrong with me the fact that I could not see an appreciable difference!  It now seems to be a common issue!

[Stu]

I do find filters to be effective under the right circumstances, but they are not magic bullets. Gerry's advice about exit pupil is very valid, keep to larger exit pupils and you will have more success as there is better illumination through the filter.

Don't forget dark adaptation! All good filters improve contrast but actually reduce the amount of light coming out of the eyepiece ie they make the view darker. It is just as important to maintain dark adaptation to get the best out of these filters.

I believe I'm right in saying that M42 is a combination of emission and reflection nebula, so it will only be the emission parts which respond to filtering. That may partly explain your indifferent results. The best results are on objects like planetary nebulae and the likes of the Veil and North America Nebula where the improvements are dramatic. The last two are some of my favourite objects; taking moon the whole of the Veil complex in one field of view in a wide field refractor with an OIII filter under a dark sky is pretty amazing. Don't write these off too soon, and also remember that you get what you pay for. The old Lumicon and current Astronomik filters do show a significant performance improvement over the cheaper ones in terms of percentage transmission of the wanted frequencies, and the cut off of the unwanted frequencies. This site may help you understand the differences between different filter types and brands.

http://www.astrosurf.com/buil/filters/curves.htm

This is an often linked to site which may give you some more information.

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

Hope that helps

[djpaul]

I tried some filters when I began this hobby and bought second hand and soon realised they were not for me so sold them on with no loss. 

However I do have some colour filters for lunar and planetary use. 

[John]

36 minutes ago, Stu said:

... the whole of the Veil complex in one field of view in a wide field refractor with an OIII filter under a dark sky is pretty amazing....

It certainly is

The illustration below is not an exaggeration of the difference in my experience. The non-filter view of this object from my back yard is probably a bit fainter than below even with my 12 inch scope but using the Lumicon O-III (the Astronomik is another really good one) does have this impact on a drk night:

[Star Struck]

Thanks for all the input everyone.

I will try using eyepieces that give me a bigger exit pupil. I will also try using the OIII filter on the correct targets to see what they can do for me.