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Skynovice

O-III Filter?

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Hello,

I'm considering purchasing an OIII filter. Up to now, I've been hesitant about obtaining one for visual observation.

Are they worth the purchase?

S.

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For me the O-III is the filter I would recommend for any serious observer of nebulae. I find the contrast boosts this filter gives provide the best results in any scope of any aperture.

I use a Lumicon myself and can't praise it highly enough, but it is a pricey filter and cheaper options offer close results.

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Hi Ya S, I have a couple of them, they vary a little in what part of the spectrum they let through and give you false colours when looking at, not so much the object, but the surrounding stars, I live under light polluted skies, so they help a little, I have the cheaper Castelli, O III and UHC these work very well but one of them came with a little loss of the coating - very small, but you had to look for it - probably down to Quality Control, but it works as well as the Baader I have, the coating and overcoating on the Baader is more robust and according to the blurb, you can clean without any fear of harm, but this as you know increases the price of them.

Generally though they make the object in the FOV more noticeable by increasing the contrast and allowing the full part of the emission through especially on objects like the Owl in Ursa Major - so the emission is there but on the downside the stars are false and the really faint stars are all but invisible, I find that if I get the object with the filter, then remove the filter, on some objects, they can just be discerned and with a slight increase in Mag.

So with your 12"  it will make a difference, but there is a lot of choice out there and all seem to work with a slight enhancement, but there probably is no better thing to enhance these objects as with a very dark sky, but as said, living with light pollution is something that, over many years of observing, I have just learned to live with, I just havn't got the contrast that a dark sky offers, so a starting point of a light background sky washes out the majority of stuff, but for me, its just about getting out under the stars and making the best of what I can see and not worry too much about the stuff I can't see, I think that why I have never bothered with a rich field Frac, I just make do with a pair of 15 x 70's.

So they may help a little, but many to choose from and each have their own benefits -  O III, UHC, UHC -S - I find the UHC - S from Baader a more natural look - or as close to natural as you can get with a filtered view - they do work with the type of emission transmission your looking for - but at the cost of a "false" view.

Hope that helps a little S and keep us informed mate.

Regards.

Paul.

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Very much worthwhile for getting the best views of nebulae, especially planetary nebulae and super nova remnants. There are a few objects where the difference with the filter is really massive and many where it's more subtle.

In smaller aperture scopes a UHC filter may be more versatile.

Neither do anything for the views of galaxies or star clusters though.

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I bought mine on the back of the last posters (above) advice to view the veil nebular and my what a difference it makes. Expensive in the Astonomiks/Lumicon brand but there are other makes that are not too far away from best.

I have used mine in the 115mm scope with very good results so you don't need a light bucket the size of coffee table to make them work.

Alan

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Hello,

I'm considering purchasing an OIII filter. Up to now, I've been hesitant about obtaining one for visual observation.

Are they worth the purchase?

S.

I presume you already have a narrowband, or UHC filter for the nebulae?

Emission nebulae typically emit energy at the 486nm wavelength of Hydrogen-Beta as well as the 496nm and 501nm wavelengths of Oxygen-III (doubly ionized oxygen).

Having a narrowband filter, which passes all 3 wavelengths, provides the maximum enhancement of the nebula's  size.

Now, some nebulae emit more energy at the O-III wavelengths than in the hydrogen wavelengths, so these nebulae will be enhanced more by narrowing the filter's bandwidth to exclude some more of the sky brightness.  Typical nebulae in this category are most planetary nebulae, and some supernova remnants.

Nebulae with primarily hydrogen emission will be aided most by an even-narrower filter known as a Hydrogen-Beta filter.

So if you get such filters for your kit, the first should be a narrowband, like the Lumicon UHC, DGM NPB, Thousand Oaks LP-2, Orion Ultrablock,

Then, if you would like another filter for more enhancement on some nebulae, the O-III filter, like the Lumicon O-III, Thousand Oaks LP-3, Orion O-III, Astronomik O-III

All of these filters reduce the light from the field of view except for the nebula.  Nonetheless, some people with small scopes (or large scopes for aesthetic reasons) might prefer

a little more bandwidth to allow through a little more star light, even though this reduces contrast a bit.

Examples: TeleVue Nebustar (narrowband), TeleVue O-III, DGM O-III, Baader UHC-S

A large scope owner, or a person taking photographs through such a filter, might prefer even narrower bandwidths on the O-III (like the Baader O-III, which is so narrow it cuts a bit of one of the two O-III lines for maximum contrast in photovisual work) and a separate filter for H-Beta (Lumicon H-Beta, Thousand Oaks LP-4).

Hope that helps clear things up.

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Excellent answer Don so it is not just a case of OIII is OIII, they all seem to be different as all scopes all not the same.

Alan

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Thanks to you all for the replies.

Yes Don, I currently use a Lumicon UHC and I've been happy with it so far, but I think I will have to take the jump and buy the O-III. At the moment, it's looking like either a Lumicon or a Baader make.

S.

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+1 for the Lumicon OIII. Your scope is plenty big enough.

You haven't seen the Viel until you have seen it through a good OIII! Worth the money for that one object alone!

Paul

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I have a 10" dob. I was going to get a UHC filter first but after reading this I am now thinking OIII. Is it a coin toss situation or would one be better than the other for me?

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You haven't seen the Viel until you have seen it through a good OIII! Worth the money for that one object alone!

Paul

I agree entirely Paul. One of the very best deep sky objects up there but barely visible with many amateur scopes without a good O-III or UHC filter (ideally the former). The transformation of the view this object with such a filter never ceases to amaze me :smiley:

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I have a 10" dob. I was going to get a UHC filter first but after reading this I am now thinking OIII. Is it a coin toss situation or would one be better than the other for me?

I got the UHC then the OIII. If you want to view nebulae, you need one of these. One works better on some objects, the other works better on others. Often the UHC will expose more nebulosity with a more natural view; while the OIII, which shows slightly less of the nebula, will expose more detail in what you can see. The link below takes you to a very thorough comparison by David Knisely (he is observing under very dark sky so take some of the descriptions with a pinch of salt for UK viewing - but the comparisons appear to be there or there abouts).

http://www.prairieastronomyclub.org/resources/by-dave-knisely/filter-performance-comparisons-for-some-common-nebulae/

Paul

PS. Contrary to popular myth. You can get some pretty good views of the Viel with a good UHC (just not as good as the OIII by a long way)

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Thanks to you all for the replies.

Yes Don, I currently use a Lumicon UHC and I've been happy with it so far, but I think I will have to take the jump and buy the O-III. At the moment, it's looking like either a Lumicon or a Baader make.

S.

Or possibly Astronomik?Their OIII works very well.

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Thanks for the advice and info everyone.  I already use a Lumicon UHC filter among the ordinary filters , but I'm going to have to buy an OIII this week.  

Thanks again.

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In that you have resurrected your own thread, I'll drop in with a bit of information for you - and all takers - that you may find very useful regards filters and their uses:

http://www.prairieastronomyclub.org/?s=Filter

The links in this site for filter-data I found excellent.

Clear & Vivid Skies,

Dave

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I have the Lumicon OIII and the Astronomik UHC - both are first rate.  How else can you see nebulae like the Veil or n. American without filters.  

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I have a UHC and an O-III filter (both fairly cheap ones). They are used a lot on planetaries and on other emission nebulae. I use the UHC a bit more, but the O-III also sees a lot of use.

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Just another one in favour of the lower priced filters - I have both the Castell "brand" and also the Baader O III and UHC - S - the Castell's work very well - the actual holders which surround the actual filter itself are a little larger than the Baader ones - therefore easier to handle, there may be a little issue with Quality Control as one of the Castell filters has a very small - and I mean small "patch" where it looks like the coating has a different "look" to it than the rest of the filter - but to be honest - It has never bothered me and I thought that its not really worth returning for a replacement - it probably only interferes with maybe  0.5% of the Total surface area of the filter and I think would not make the slightest difference to the views - the views through the Castell and Baader are much the same, probably only a slight decrease in contrast in the UHC - S (due to the way the filter works) with a slightly increased sky background brightness (again, due to the way the filter works) compared to the more aggressive O III's.

Paul.

Edited by Northern Soul man

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..........I was reading an article  this morning that explained the merits of the O III filter, but it appeared to me  that the UHC was more favoured, and  that the O III was not  not an essential filter !

I would also assume that a  dark sky  needs to prevail,  to get the best result, and that the telescope needs a decent amount of aperture, 

Edited by Charic

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+2 for the Lumicon, Baader is too narrow in my opinion.

I agree on both these points. The Astronomik O-III is really good too - mine has shown some stunning views of the Veil nebula and works well with smaller apertures too :smiley:

Unfortunately the Lumicon and Astronomik filters are quite expensive though.

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Never had the chance to use one on my scope yet.. Must stick one on my Christmas list,oops shouldn't of said that word!

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A while back I purchased a Lumicon OIII and I am comparing it to my Astronomik. Both are excellent and a pattern is emerging, but this was expected.

I would think any OIII with good glass/coatings/bandpass and high transmission would be an asset to own. To the OP, I use my OIII a lot- last night under the full moon I could still faintly see the Veil in the 10"- but it seems that dark skies allow more and fainter objects to be seen, and this is where they see the most use.

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Are you doing a report on the subject?....please,please pretty please;)

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