OIII Filter and small fracs

[Hex]

I'm sure I read somewhere that these filters were only any good in scopes 8 inches and above, anyone used one in a ED100 or similar small scope?

[Carbon]

Well they are more practical to use in large aperture scopes due to it's extreme narrow band nature.

My Baader O-III filter came with brief information stating it was recommended for scopes 8" and larger.

[JamesF]

I've not used mine in an ED100, but for visual use I think they just cut out too much light to be used in a small scope. Remember that an 8" scope will collect four times as much light as your 100mm one.

James

[John]

I've used 2 types of O-III filter with my 4" refractor, a Baader O-III and my current Astronomik O-III. The Baader dimmed the surrounding stars too much for my taste but the Astronomik is excellent. The band pass widths of filters of different brands do vary so it's worth checking the specs. The Baader is known to have a narrower band pass width than most O-III's so would probably be more satisfying in larger apertures where there is more light to play with.

[RikM]

I have used my SkyWatcher Oiii filter with an ST80 from a dark site and was surprisingly effective. The SW also has a wider bandpass than the Baader filter.

[Hex]

Ok chaps thanks for that, very useful.

[John]

A good alternative would be a UHC filter which would work well with a 100mm aperture. The Skywatcher and Castell ones seem well regarded and not uber-expensive. I've also used an Orion (USA) Ultrablock in a 4" refractor and been pleased with the results.

[catburglar]

I use a Castell OIII with an ZS80- all of the Veil nebula and North America nebula seen from suburbia. No hesitation recommending this over a UHC. For me, the UHC doesn't add much, but maybe it depends on the stuff that's causing the LP.

[John]

I don't think either the O-III's or the UHC's deal with Light Pollution. LP filters are different.

I agree that an O-III is more effective on the Veil and some other nebulae than a UHC but a UHC still provides significant contrast gains and is arguably more versatile on a wider range of objects than an O-III. Ideally, it's good to have both types !

[swamp thing]

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I don't think either the O-III's or the UHC's deal with Light Pollution. LP filters are different.

They do in a way John as they're filtering out all light except the bandwidths permitted.

So in effect are acting as LP filters indirectly ish

Not the same, as you say, but they certainly help a great deal. They work considerably better than any LP filter I've ever used (they seem to do almost nothing visually).

The problem with using UHC and O-III filters from urban environments is they darken the view considerably, so good dark adaption is essential. This is very difficult to achieve from an urban environment, some type of head cover may be needed to get the most out of a filter.

[John]

I agree they enhance the views of nebulae in light pollution but under dark skies they work even better

I guess a good LP filter should reject the light emitted by light pollution sources so should, in theory, enhance the views of all DSO's, not just nebulae, viewed under light polluted conditions.

I also agree about good dark adaptation being essential to get the best from UHC and O-III filters and also they seem to work better with certain exit pupil sizes.

As usual, nothings really simple

[Hex]

So which would you go with do you think if you were buying just one, the UHC or the Astronomik O-III John?

[rwilkey]

I use the Sky Watcher OIII filter quite successfully with my C100ED, no hesitation in recommending it. I too have heard that the Baader are more narrowband.

[ollypenrice]

I'm mystified by this 8 inch claim and would dismiss it, quite honestly. I use a Baader 2 inch O111 to view the Veil, for example, in anything from our 20 inch Dob to our TV Pronto (70mm). In the little scope it shows the entire loop in a single field. It also shows the Rosette in the 70mm. It was even better in our 4 inch Genesis but I sold that. Not to worry, the O111 is great in the Pronto.

Olly

[Stu]

I use an OIII with a 4" apo with good results so I agree that it should not be treated as a rigid rule.

I do also agree that you need good dark adaptation to get the most out of them in smaller scopes, which is tricky to achieve under normal UK skies. Olly, I guess your dark skies mean you get very good performance which ever scope you are using?

Stu

[John]

So which would you go with do you think if you were buying just one, the UHC or the Astronomik O-III John?

Well I'm biased as I have the Astronomik O-III in the 2" size

Prior to that I had an Orion Ultrablock which is very similar to a UHC. I liked that one a lot too. Prior to that I'd had a Skywatcher UHC, a Baader O-III, a Celestron O-III (which was the same as the Baader !), a Baader UHC-S and a Telescope Services UHC (which seemed identical to the Skywatcher UHC).

I'm staying with the Astronomik now as it delivers great views in all my scopes, 4" - 10" in aperture.

[Hex]

Well that just goes to prove the old adage " if you need a straight forward answer, to a straight forward question, ask an astronomer"

[Carbon]

I'm mystified by this 8 inch claim and would dismiss it, quite honestly. I use a Baader 2 inch O111 to view the Veil, for example, in anything from our 20 inch Dob to our TV Pronto (70mm).

Well, it certainly could apply to my backyard sky conditions. I was hoping to detect the Veil after I got the Baader O-III but no luck with both my 11" & 12" scopes.

Years ago when I had a Pronto and TV-102 even the mildest LP filters were pretty much ineffective from my urban back yard.

Astronomik O-III filters are rather pricey here in the U.S. and if it were comparable in price to the Baader, for instance, I probably would have gone with the Astronomik O-III.

Optcorp sells them here but they're close to $200 for the 2" filter vs. $117 I paid for the Baader O-III 2" from a different dealer. BTW, it also states that the Astronomik O-III filter is recommended for apertures over 6".

[John]

........ BTW, it also states that the Astronomik O-III filter is recommended for apertures over 6"......

Yes, I've seen that advice too. The Astronomik works (for me at least) better than any other UHC / O-III filters I've used and it's "party piece" is when I use it with my 4" F/6.5 refractor and Nagler 31mm to show the whole of the Veil nebula complex in the same field of view - east + west segments and Pickerings Wisp. Absolutely superb sight

[crazyjedi]

Is there a particular OIII that anyone can recommend for use with a six inch newt under lots of light pollution?

I currently us a Baader UHC-S with some success but try as I might I cannot see the North America Nebula I doubt I'll see the Veil Nebula with my scope under my sky but it'd be fun to hope

[John]

A Baader UHC-S showed me the Veil nebula with 80mm and 100mm scopes so you will be able to see it with your 6", unless you have lots of light pollution - it does need dark skies. The NA Nebula is much harder to spot I found - took me years and then it was 15x70 binoculars that did the trick. I've since seen it with a 4" refractor and O-III filter but it's much less distinct than the Veil.

That said, the UHC-S is not the most effective you can use with a 6" scope - a Skywatcher or Castell UHC or an O-III by those brands will enhance the contrast more. But the Veil should be visible with your scope and the UHC-S filter. It's a very large object though so use your lowest power, widest angle eyepiece.

[cotterless45]

We've seen this a few times by eye at the edge of town.Seeing conditions will dictate your view,these presently alternate from great to grot.

Nick

[RikM]

My Skywatcher Oiii works well with my 150P Newtonian. The veil can be picked out quite nicely even from the outskirts of Glos. Never seen the NA neb though. The other thing I like about the SkyWatcher is that it is quite a chunky thing, so easy to handle with cold hands or wearing gloves.

[crazyjedi]

Thanks guys. I'll probably get myself the SW OIII then.

The most frustrating thing about the NA is that the open clusters in and around it can be picked up but the nebula itself is elusive no matter how hard I strain my good eye at it.

John my lowest power EP is an ES24mm 68 degree. Probably not long enough or wide enough to fit the Veil Nebula in I reckon but I can't get much longer than 30mm with my scope at 1.25 inch EP's (my UHC-S is 1.25 inch)

[Hex]

I take it to get the best out of a UHC I would be better off using a 2 inch number?