OIII Visual Filter

[Mike73]

Interesting thoughts. I spent some quality time with M27 last night and tried OIII and UHC to see what could be seen at a leisurely 100x. Both filters showed more detail. But without the surrounding starfield, the image was strangely dead. I still can't get my head around seeing green stars.

Whilst these two filters have transformed my viewing of nebulae, there are some that work better as nature inteded.

Paul

I found both Lumicon and Astronomik UHC and OIII filters gave a green cast to stars and nebula, it wasn't something that I found off putting but I'd rather a more neural appearance so I'm now using a DGM Optics NPB filter which doesn't give a green cast and is slightly better than my old Astronomik UHC for contrast.

http://www.astronomy.com/~/media/import/files/pdf/8/c/7/0805_nebula_filters.pdf

I've also found that at really good dark sites I just don't need any filters for the big bright emission nebula like M42 but as soon as any light pollution comes into play I do need a filter.

[John]

Yup. I prefer the UHC because it kills 90% of the light pollution without dimming the stars too much. I find the OIII is great at isolating nebulosity but without the stars (or with very dim stars) the view isn't so pleasing from an aesthetic point of view. At least to my eyes

All the best

Tim

Try an Astronomik O-III if you get a chance sometime Tim. I preferred UHC for the same reasons that you mention above until I used the Astronomik O-III. 

[Paul73]

HI All,  The clouds parted here and there for myself and friend to do quite a bit of observing.  Here's the portion that concerns the Astronomik UHC filter.  The telescope I used was an Explore Scientif ES102ED.

"The last object I viewed was simply to try out my new Astronomik UHC 2" filter. I placed it just before the diagonal, and used my lowest power, a 21mm Orion Stratus eyepiece. The object was NGC6992, a part of the Veil Nebula,  and the results were totally stunning. I could see the object without a filter, and it was quite visible, but with the filter, everything just jumped out and grabbed you. I could see so much detail. That is what astonished me. It is by far, better than the Orion UHC. I'm not putting down the Orion filter. It's just that this new filter I have brings so much more detail out. The Orion pretty much just enhanced what you could already see without a filter, not providing any appreciable detail.

We then put the filter in the C14, and the Wow factor went from 10 on the 10 scale to about a 20 on the 10 scale. Yeah, I know that is stupid to say, but the view was incredible. Details seen in the C14 were putting what I had just seen with my 4 incher to shame. You could see so many wispy featherlike features. My friend then scanned over to 6960, and what a neat looking thing. I could only make out the bright star and the part that looks like the star is spewing something in a stream that looks like a very straight "S""  Caley

Glad that you are enjoying your new filter. Sounds like you gave it a proper first light workout.

Paul

[allen g]

Caley, I have the lumicon 0111 and used it with my tv np101 and nagler to see the entire veil (used it last night on M 8). Also, have the astronomic uhc which works as well with my 4" scope. Needless to say dark skies are best for these filters but they do work in a 4" refractor.

[astronomynut]

Allen, Thanks so much for that information.  I will have to wait at least a month to obtain the OIII filter.  I am saving against a rainy day, so I only allow myself one purchase for my addiction per payday.  Needless to say, that is a very difficult thing to do, but an absolute must.  I look forward to comparing the UHC and OIII filters on various objects.  I also plan to get an h-Beta filter to round out what is needed to view the various nebulae.  The h-Beta probably will be good on only a few objects, but it is nice to at least see something other than a super faint smudge that no filter shows on many of these faint nebulae.  Caley

[Daniel-K]

Well I took delivery of a a astronomik uhc and im going to try it out tonight in the 14" dob

Im looking forward to it now after reading this thread

[AndyWB]

And I got an Astronomik OIII filter, and was using it last night. Given the success I had with nebulae, I think it worked rather well; certainly I couldn't point it near Deneb without some kind of nebulosity.

[Don Pensack]

What you want in an O-III filter is:

--steep drop-offs to sides of transmission curves

-->90% transmission at both 496nm and 501nm

--not more than 12-15nm FWHM bandwidth (50% transmission points).

There is no minimum aperture for an O-III filter, but magnification must be kept low in very small apertures.

I've use one in a 50mm finder, and it worked well.

http://www.karmalimbo.com/aro/pics/filters/o3a.jpg

http://www.karmalimbo.com/aro/pics/filters/o3b.jpg

are two pages of O-III light curves overlaid.

The charts are getting a little dated because some of the filters are gone and there are many new ones.

Some notes on the charts:

TeleVue, Astronomik, Andover, IDAS all extend too far up.

Meade (no longer made) and Orion extend a little too far down.

In the second group, all exclude the 496nm line, so are better used as photographic filters.

The necessary transmission is found in Lumicon, TeleVue, and Astronomik filters.

The consensus seems to be that only a few O-III filters meet most or all of the requirements:

Lumicon O-III (the gold standard)

Thousand Oaks LP-3 (a little wide, but not as wide as TeleVue)

Orion O-III (a little lower transmission but excellent control of bandwidth)

There may be some other new filters (Denkmeier, et.al) that may meet the requirements, but I have seen no tests or recommendations.

A good choice for apertures of 5" and down would be the TeleVue.  It has high transmission and the slightly wider bandwidth won't darken the field quite as much.

For 6" and up, though, the recommendations hold very well.

For very large apertures (say 25" and up), the single-line photographic filters may work well, though they will exclude some O-III details.

[faulksy]

my baader oiii seems pretty good, some faint stars are invisible, noticed you couldt see the stars in the dumbell nebula with the filter but very easy without

[jetstream]

Don,how much darker will the Lumicon show the background compared to my Astronomik or similar?Are stars still visible in your scope with the Lumicon?

[Stu]

Gerry, I still see stars quite well with my Lumicon, even in the 85mm

[jetstream]

Thanks Stu,I was wondering how much darker the Lumicon shows.Some experienced observers have said not much difference between the two brands,but as always I'm curious.I think a darker background might be an asset under certain conditions,but is probably spitting hairs.It will be expensive for me to try.....

[Stu]

The Lumicon does seem to have one of the narrowest bands, with high transmission in the desired frequencies and steep cut off.

I managed the East and west Veil in my 85 with mine under ok skies, but nothing special. It is much better than the SW one I had previously

Stu

[Rustysplit]

I would agree with Don, in that the Orion is up there with the Lumicon. Last year, I think, Si and I did a side by side comparison between the 2 in the same scope with the same ep's. The Lumicon "maybe" edged it for the win, but the Orion ran it extremely close. So close that if you did not know which one was in at the time, it would not bother you.

[estwing]

Can't get a lumicon anywhere at the mo...

[John]

I would agree with Don, in that the Orion is up there with the Lumicon. Last year, I think, Si and I did a side by side comparison between the 2 in the same scope with the same ep's. The Lumicon "maybe" edged it for the win, but the Orion ran it extremely close. So close that if you did not know which one was in at the time, it would not bother you.

Is that the Orion (USA) O-III V's the Lumicon O-III Alan ?

I seem to recall Steve (swamp thing) having a similar result comparing the Astronomik  O-III with the Lumicon O-III and yet there appears to be quite a difference between them looking at the band pass data charts for the two.

[Rustysplit]

Yes John, sorry should have made that clear. Orion USA 0-III vs Lumicon 0-III.

the thread is here ....http://stargazerslou...ii-filterfight/

[Don Pensack]

Keep in mind that a wider O-III filter may be useful in certain circumstances:

--higher magnification when you don't want the field to be as dark as possible

--a large aperture under dark skies, where the view without filter is already great and you just want to see more nebula details

Normally, I prefer a narrow O-III filter like the Lumicon (12nm) or Orion (15nm), but I do sometimes use a TeleVue O-III (23nm) to see more stars and

a brighter overall field of view.  It is having a preference like that that points people with small scopes to a wider filter.  Otherwise, a narrower

filter (so long as both496nm and 501nm line transmit at >90%) is always better at showing nebular details.

Having a wider filter doesn't dim the nebula, but it does reduce its contrast with the background sky.

IF you know the relative strengths of the emission from the nebula at 486nm (H-Beta), 496nm and 501nm (both O-III), you can make an intelligent selection of a filter to use on that nebula.

For instance, if the nebula emits almost all of its O-III energy at 501nm, and even-narrower photographic O-III filter (transmitting only the 501nm line) will provide the ultimate contrast.

There are on-line sources for these spectra.

But if you don't know what wavelengths are strong in the nebula, best to start out with a Narrowband filter (486+496+501nm) to check the visibility of all of the nebula before switching to an O-III filter (496+501nm).

[John]

Very interesting and useful advice Don 

I guess ideally you need a selection of O-III and UHC filters to choose from, depending on the target object and the scope to be used. Gets kind of expensive with the premium brand filters though   

[swamp thing]

Hmm perhaps the aperture I used when comparing the two filters was insufficient as to show any significant differences (I only used a 120ED frac) perhaps a further comparison through the 20" reflector will yield a different result.

We shall see in due coarse.

[faulksy]

very soon steve