Best filter: UHC, OIII or H-beta?

[skysurfer]

Well, I have a small 1.25" Lumicon UHC filter, but it vignettes in my 24mm ep. So I want to buy another one of 2". I take an OIII or H beta also as an alternative. Even higher contrast and a H-beta even should show the Horsehead and California nebula. After reading this CN article (http://www.cloudynights.com/item.php?item_id=1520) discouraged me from H beta and I prefer a UHC again. I'll use it with:
40cm Dobson at home, moderately light polluted and 10cm Genesis or 15x70 binos on a dark location.
What would you recommend?

[DJ N]

I recently purchased a 2" DGM Optics NPB filter for use with my C11 and 41mm Panoptic, and at this stage I am very impressed. I have only had limited time with it, but for example, Tarantula takes on a 3D appearance and is almost photo like. I cannot wait to see M42 with the filter in place!

Not sure how the others compare, but looking at a couple of reviews on Cloudy Nights, it seems the two to have is the DGM NPB and the Lumicon OIII.

Hope this helps,

Cheers,

Daniel

[mental4astro]

I'll relate things through my experience with the three filters I have. I've used all three in my 17.5" dob which is not far off from your 16". Thing is too, big $ ain't necessarily better. All three 2" filters I have are made by the same company (Omega Optical) even though it has a high end brand attached to it (DGM). Of my three filters, only one is from this 'high end' line. I've put a link to where I picked up each filter from too.

I have a Hbeta filter (http://www.ebay.com.au/itm/Optical-Filter-486-Astronomy-Hb-Narrow-45-48mm-2-/350238097824?pt=Educational_Toys_US&hash=item518bd141a0), and it gave me the best image I've had of the Horsehead. It is comes from Omega Optical. Great filter, but it is the least used.

My UHC type is the DGM NPB (http://www.ebay.com.au/itm/NPB-2-0-DGM-Optics-Nebula-Astronomy-Filter-/161125373156?pt=LH_DefaultDomain_0&hash=item2583d214e4). Nice filter but really best exploited under dark skies. Different beast from an OIII, and so it should be.

My third filter is an Omega Optical special. As they make filters not just for themselves, but for other brands, they have the means of making really special items. This sees my OIII filter have the added transmission of Hbeta! A typical OIII filter won't show the Horsehead. This OIII + Hbeta (http://www.ebay.com.au/itm/Filter-486-Astronomy-Hb-OIII-Nebula-II-48mm-2-/350238139324?pt=Educational_Toys_US&hash=item518bd1e3bc) does! This is my preferred filter for use from home under light polluted skies.

I did a side-by-side comparison of all three filters just on two months ago with all the above three filters on the Horsehead. ALL three showed the Horsie. The dedicated Hbeta was the clearest (just remember that the exercise of looking for the Horsie is one of looking for a bugger all difference of black on black), but the ease of viewing B33 was just as easy with the NPB as this OIII + Hbeta filter. Not just my opinion - there were three other people with me that night that all looked through all three filters too. I've had this filter pooh-poohed by supposedly "knowledgeable" folk who never used this filter, but felt qualified enough to dismiss it outright. Sorry, but my opinion of these people has dropped considerably.

Hbeta filters are great, but they don't get used much. They are very narrow with the selection of light that gets through, and are exclusively a dark sky option. UHC filters are more practical, can be used under light polluted skies, but perform best in the dark. OIII's are my choice for urban skies, but are excellent for their purpose in the dark too. Three very different beasties with three very different applications. Not one right or wrong choice, that is something you need to decide for yourself. And certainly nothing wrong with a dedicated Hbeta filter, particularly if you've got the aperture grunt. Even though it won't get used as much as the other two, for what it does nothing else touches it.

Mental.

[glend]

I will second Mental's statements. I have both the DGM NPB and their OIII. I prefer the NPB for general use on nebulas of most varieties, and for the Horsehead it is the pick - but be prepared with dark adapted vision, avoid zeta orion flooding your EP and use averted vision technique.

[mental4astro]

You also need to be aware of the different roles each filter has. An OIII will show up planetary nebulae, but not an UHC type. UHC filters are best for emission nebulae, an OIII will do so too, but not as dramatic. Very different applications.

This following link to the Lumicon filter guide is a great tool for familiarizing oneself with the many different filters. It will help you understand the differences between OIII, UHC & Hbeta:

http://www.lumicon.com/store/pg/15-LUMICON-Nebula-Filters.aspx

[Camelopardalis]

I've really enjoyed the views of the Tarantula, Carina and Orion nebulae through the NPB, most recently in my C11 they were unreal - I'd never seen anything like it from one of my own scopes. Mental's 17.5" is a beast :D

So far, I've found I've preferred the views with the NPB over the OIII on the above, but I've only had the OIII for a couple of sessions so it's early days. The NPB just looked more wispy and extended. No doubt my choice of subjects is a factor too!

[skysurfer]

These three objects look even in my 10cm Genesis superb with UHC. But what is an NPB filter ?

[Camelopardalis]

See Mental's first post, there's a link there ;) basically it's a narrow pass band filter, similar to UHC (UHC being the name used by Lumicon)

[casstony]

under moderate light pollution my 1000 oaks OIII shows the carina nebula far better than my DGM NPB in 10" or larger scopes.

[bytor666]

I used to own the DGM O-III and tested it against the Orion Ultrablock which is a Narrowband filter. Both worked almost exactly the same in the bandpass dept, but the Orion gave a "green" hue, while the DGM O-III gave a more "natural looking" view.

Tha bandpass on the Omega O-III is too wide to be considered a "true" O-III filter.

[mental4astro]

Mark, two things on the Omega OIII + Hb: you're missing the point here on this filter - with any filter there is give and take. While in the strictest sense it may be not as you say a "true" OIII, the band pass of Hb is an added bonus. Second, have you tried one? If you haven't, what do you think you will see through it?

It is disconcerting when people are all to quick to dismiss something without trying one. Break the chains, people. If money is a concern for someone looking for a filter, this OIII + Hb filter (which is what it is labelled as) I think is a fantastic solution. I have looked through "true" OIII filters, and this filter does very well - the tiniest bit brighter. BUT, if an additional UHC filter is too expensive, or just too many filters, and you want to see something like the Horsehead, this OIII + Hb filter will show it, and just as clearly as a dedicated UHC filter. As a practical and economical filter compromise, this one is excellent.

This is why Omega offers this filter under its "Omega" brand, not their "DGM" brand where you will find a strictly "true" OIII filter. But what they haven't done, unlike some other more popular brands, is mislabel their filters as one company labels their "UHC" and it really is a broad band LPR.

Scepticism is mandatory. Experience is Nirvana. With the amount of eyepieces you've gone through Mark (and you've had one or two, ;)), you certainly would know this. This OIII + Hb is a different take on astronomical filters. Bloody good one I reckon.

[bytor666]

Omega is the same company that makes DGM filters Alex. If you had of read my previous post I did say I used to own the Omega / DGM O-III filter. Both are one and the same filters IIRC.

[mental4astro]

No, they are different filters. The DGM is much tighter in band through pass (http://m.ebay.com.au/itm/160462186370?nav=SEARCH&sbk=1) than the Omega OIII Hb (http://m.ebay.com.au/itm/350238139324?nav=SEARCH&sbk=1). Specs are distinct. But if I am mistaken, I am happy to be shown otherwise. I don't see where you say you've had an Omega OIII Hb filter, unless it is through the initial suggestion that these two filters were the same one. I also mentioned the Omega ownership of DGM in post No 3 of this thread, first paragraph.

I'll search out some other mentionings of the DGM OIII filter - if I remember correctly, it too is highly regarded as one of the best OIII filters on the market.

[bytor666]

Check out this thread below:

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5919335/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1

And something else also!

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/6276558/page/0/view/collapsed/sb/5/o/all/fpart/1#Post6276615

Cheers,

[mental4astro]

Mate, I don't get it. Do you ever read what anyone writes, here on IIS or CN?

Just that first link you posted confirms everything I've written. Even the only thing we agree on, that Omega Optical owns DGM, yet you carry on like I refuse to acknowledge this.

[bytor666]

I give up.

No point in going on about this.

Cheers,

[Profiler]

For what it is worth I have found the Astronomik CLS surprisingly good for light polluted suburbs and then their O-III.

I have both the DGM and Astronomik O-III and IMO the astronomik tends to be better for me.

[Don Pensack]

Try this thread on IIS:
http://www.iceinspace.com.au/forum/showthread.php?t=117915
Then, for recommendations on types for each nebula, see:
http://www.prairieastronomyclub.org/resources/by-dave-knisely/filter-performance-comparisons-for-some-common-nebulae/
Some recommended brands (in order):
Narrowband: DGM NPB, Lumicon UHC, Orion Ultrablock, Thousand oaks LP2
O-III: Lumicon, Orion
H-Beta: Lumicon, Thousand Oaks LP4
Broadband: Lumicon, Orion

[AG Hybrid]

A cheapie GSO blue filter. Makes splitting uneven binary stars easy. With a blue filter splitting Sirius is a doddle. I did it at 107x last night with a Delos 14mm and a blue filter.

[Don Pensack]

This might help:
http://www.eyepiecesetc.com/Choosing_a_Nebula_Filter_p/nebula-filters-explained.htm
If you buy just one: the UHC.
If you buy a second filter for more specialized use: An O-III
If you have money to burn for a handful of objects: H-Beta.
Lumicon is the "Gold Standard", but there are other good filters.
To see comparisons in spectral charts, see:
http://www.karmalimbo.com/aro/pics/filters/narrow.jpg
http://www.karmalimbo.com/aro/pics/filters/o3a.jpg
http://www.karmalimbo.com/aro/pics/filters/o3b.jpg

[astro744]

If your 24mm eyepiece is the 24mm Panoptic then it has a 27mm field stop diameter and this is almost maximum for a 31.7mm (1.25") barrel eyepiece.

You will therefore find that just about any filter on the market will vignette slightly with this eyepiece. However your UHC may also have a thicker cell wall in which case it will cause significant vignetting. I have only seen this once with Lumicon on a 2" Comet (Swan band) filter that had a much thicker cell wall than the other 2" narrowband filters. It could be an older filter from an earlier production run.

I concur with others recommending Lumicon as they have been making filters for a very long time and do produce a very fine product. Of the Lumicon filters, I find my first choice on my larger aperture telescope (25cm) is the Lumicon O-III and whilst this filter also works well with my smaller refractor (10cm), I prefer a more gentle filter on it and then choose the Lumicon Deep Sky filter which basically just darkens the background a little and gives a more natural view.

However, there is a very good alternative that you may like particularly on your Genesis and that is the Tele Vue Bandmate O-III. Some will argue that this is not a true O-III filter since it is a little wider in bandpass but it has been designed to give a very natural view. Also this filter does not show red/blue fringing on bright stars as some other filters do. The trade off though is a more greenish but sharper view. See http://www.televue.com/engine/TV3b_page.asp?id=24&Tab=_test#.UytXYKiSy5I

I really enjoy views through the Tele Vue Bandmate O-III and a variety of telescopes from small refractors to larger reflectors. You would not be disappointed with Lumicon or Tele Vue.

Another option for your 40cm telescope is the Thousand Oaks O-III. On a 25cm telescope this filter gives me the best contrast with jet black background and stunning nebula (Eta carina is sensational!). This filter would be ideal on 40cm with more light to play with. I find though that this filter is a bit too severe on smaller telescopes (for my liking at least). (I'm not sure if a tighter bandpasss or less transmission gives the jet black).

Exit pupil is important and the more the better I find and this is where larger aperture helps but the filters do work well in smaller 'scopes, just some better than others.