OIII Visual Filter

[astronomynut]

I'm in the process of trying to find quality filters.  So far I have picked up an Astronomik UHC filter, which hopefully will open up details on some nebula.

  But I am running into problems trying to determine the possibility of using an OIII filter with my Explore Scientific ES102ED.  One brand, I will not name brands, says that OIII filters only start being  useable with 6 inch telescopes.  While other brands have no mention of effectiveness based on aperture.  This filter, as I understand it, will be most effective on Planetary Nebulae, though some emission nebulae may benefit.

 Has anyone  had success using an OIII filter on their four inch refractor?  If so, can you provide a link to the filter, so I may take a look at it's specs and information.  Caley

[alan potts]

I know for sure one of my fellow Moderators uses a Olll on the Veil Nebula with a 4 inch from his home. Now I do not know what type of skies he has but if I recall he has not got a 100% success rate with this combo. I use a 4.5 inch with the Astronmiks Olll and see it every time, without the Moon in the mix.

I am sure he will tell you the exact story later on but if you have a good dark sky I would think you will see this target for one.

Alan.

[Stu]

I use a Lumicon OIII in a 106mm triplet..... But not from home. My skies are around 4 to 4.5 mag and I just don't get dark adapted enough to see anything.

Under a dark sky is very different though, once properly dark adapted I can see the whole of the Veil nebula in one 3.6 degree fov, lovely. The NA nebula is fabulous too.

I know John does likewise and think his home skies are a fair bit better than mine.

I think the thing is, they still work in smaller scopes but you need to be able to get you eyes adapted

Stu

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[swamp thing]

As above good dark adaption is required to get the best from an O-III filter. I use mine with everything from my naked eye right up to my 20" reflector.

[Stu]

I find this site interesting when trying to understand the different filter types and brands.

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

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[Paul73]

I find this site interesting when trying to understand the different filter types and brands.http://www.astrosurf.com/buil/filters/curves.htm

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What a difference!

Taking the two extremes (OIII) of the Astronomic and the Meade filters. What would the visual difference??

It appears to be letting through more Red than Green!!

Paul

[Stu]

Yes, that's why it is interesting to understand the curves of each filter. Some filters promoted as OIII are more like UHC or even broader in their bandpass.

The Meade OIII does not have particularly good throughput in the OIII frequencies, and as you say let's the Ha through aswell which is a normal feature of UHC.

I would expect it to have relatively poor contrast on objects like the Veil, and to perform more like a broad pass UHC filter. Not one I would consider!

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[astronomynut]

Thanks Everyone,  Where I observe from varies from Bortle 3.5 to 4.5.  The only problems are people with their car headlights intruding into the observing and AP areas.  If we can get a long period between inconsiderate people in their cars, we get fairly dark adapted.  We can actually see the Veil Nebula very faintly without any aid.  I am just trying to find a way to improve my viewing of these gaseous treats.  Caley

[Paul73]

These guys may be a bit optimistic with their transmission percentages. Or, Lumicon have a significant variation between the performance of individual filters.

My Lumicon OIII has 94.7% at 496nm and 94.2% at the 501nm points (written on the back of the box, I assume, by a Lumicon tester). The curve shows about 98% at 496nm in the link.

Ok. I have just set a new benchmark in pedantry. And it is off thread.

Sorry

Paul

[Stu]

Thanks Everyone, Where I observe from varies from Bortle 3.5 to 4.5. The only problems are people with their car headlights intruding into the observing and AP areas. If we can get a long period between inconsiderate people in their cars, we get fairly dark adapted. We can actually see the Veil Nebula very faintly without any aid. I am just trying to find a way to improve my viewing of these gaseous treats. Caley

I'm sure if you can see it faintly without a filter then you would see a benefit with. Worth a try...

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[Stu]

These guys may be a bit optimistic with their transmission percentages. Or, Lumicon have a significant variation between the performance of individual filters.

My Lumicon OIII has 94.7% at 496nm and 94.2% at the 501nm points (written on the back of the box, I assume, by a Lumicon tester). The curve shows about 98% at 496nm in the link.

Ok. I have just set a new benchmark in pedantry. And it is off thread.

Sorry

Paul

I'll check the percentages on my Lumicon. There must be some variation otherwise they wouldn't bother marking each one....

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[John]

I'll check the percentages on my Lumicon. There must be some variation otherwise they wouldn't bother marking each one....

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Thats my understanding with Lumicon - each one varies but each is measured and the %'s written on the box of each one.

I'd not loose much sleep over a couple of % as there is more variation than that in eyepiece throughput / primary reflectivity / etc, etc

[astronomynut]

I continue to browse around the net for information on OIII filters.  It seems that aperture is not a limitation to a 4" APO refractor.  Seems that like was mentioned, observing sites are very important, dark adaptation, and additionally, how much magnification you use.  Lower powers for the smaller aperture telescopes seems to help, or so I have read, generally somewhere between 3 to 6 power per inch of aperture.  I think I will put one on my wish list for next month.

  Another problem is that the filters vary so much between manufacturers/brands.  Some people are very happy with the Orion OIII, and then there are some people who are married to a particular brand, regardless of the performance

  I think I need performance that allows the OIII spectrum to come through, but I don't want things so dark that I cannot see stars.  I guess what I am asking is what would be a middle of the road OIII filter, one that boosts the OIII spectrum, but allows some other things to come through.

  If my guess is right, those filters who completely block all other light, are probably better suited to CCD photography where you want to isolate particular bands, so that you can integrate them into the picture you desire.  I don't know a thing about CCD photography, so I am only speculating.  Caley

[John]

My Astronomik O-III filter works excellently with my 102mm refractor (as mentioned by some of my forum colleagues above) as well as my larger aperture scopes. It's band pass width is wider than most O-III filters though. It's also rather expensive.

Before I had the Astronomik O-III I used a somewhat less expensive Orion Ultrablock filter with the 102mm scope. This is a UHC-type filter admitting both the O-III and H-Beta bandwidths and I enjoyed the views of nebulae through that one as well

[Stu]

The differences are quite interesting, particularly between the Lumicon and Astronomik UHC filters. The Lumicon just allows the Hb and OIII doublet, whilst the Astronomik also passes the Ha.

The Lumicon OIII and UHC are very similar infact. I have both and will do some experimenting but it may be that the Astronomik UHC is worth looking at too.

I checked mine, and the % are all above 97, so seem pretty good.

Stu

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[John]

Good figures I think there, Stu.

David Knisely, the filter "Guru" on Cloudynights does not like the Astronomik O-III filter much because he feels it's band pass width is a bit too generous for an O-III. He may have a point but I love it as it serves as a single filter solution for me, someone who does not use filters much

I've yet to see much at all through my Lumicon H-Beta 

[Paul73]

I checked mine, and the % are all above 97, so seem pretty good.

Stu

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I've been sold a pup!! Although visually I doubt that you would see much difference.

I wonder what the manufacturer regards as the minimal acceptable? I'll ask them.

Paul

[astronomynut]

I have the Astronomik UHC filter, but have not had a chance to use it. If the clouds go away, a friend has invited me up to the local observatory

to do some work on equipment and a little observing. I will let you know how it compares to his Orion UHC. Caley

[John]

I've been sold a pup!! Although visually I doubt that you would see much difference.

I wonder what the manufacturer regards as the minimal acceptable? I'll ask them.

Paul

Lumicon have changed their bandwidth and coating specs in 2001 and then again in 2005. The latest versions show the highest band pass %'s. Yours may just be one of the earlier versions.

[jetstream]

Good figures I think there, Stu.

David Knisely, the filter "Guru" on Cloudynights does not like the Astronomik O-III filter much because he feels it's band pass width is a bit too generous for an O-III. He may have a point but I love it as it serves as a single filter solution for me, someone who does not use filters much

I've yet to see much at all through my Lumicon H-Beta 

BigMaks link does have good figures.I read those CN posts about the Astronomik too,but it does work.Well.No doubt the Lumicon OIII works well too.These 2 brands seem to have the most positive,consistent reviews. I don't understand how a tight UHC filter can be praised,and then a "looser" OIII criticized that is tried and proven on appropriate objects.

My Astronmik Hb has a wider passband than some and yet experienced observers claim the HH can be seen with a UHC,and yet this Hb filter is said to be not optimum....I have tried this Astronomik Hb filter briefly and have seen some nebula in Auriga,notably the Flaming Star neb.2 other faint ones in there as well,not too bad for a 10" and an 18mm BCO.

Tried and proven is the way to go IMHO.

[John]

BigMaks link does have good figures.I read those CN posts about the Astronomik too,but it does work.Well.No doubt the Lumicon OIII works well too.These 2 brands seem to have the most positive,consistent reviews. I don't understand how a tight UHC filter can be praised,and then a "looser" OIII criticized that is tried and proven on appropriate objects.

My Astronmik Hb has a wider passband than some and yet experienced observers claim the HH can be seen with a UHC,and yet this Hb filter is said to be not optimum....I have tried this Astronomik Hb filter briefly and have seen some nebula in Auriga,notably the Flaming Star neb.2 other faint ones in there as well,not too bad for a 10" and an 18mm BCO.

Tried and proven is the way to go IMHO.

With filters I think a lot is down to personal preference Gerry. 

Mine is that I like to see a fair amount of well defined stars to set the DSO in context and a slightly wider band pass width allows that to happen, plus good quality optical glass, polish and coatings of course.

Others are happy to get the maximum enhancement of the contrast of the nebulosity and are happy to sacrifice some or most of the background stars to get that. 

We are, again, fortunate today that the astronomy equipment market caters for these preferences so you can read the reviews and the specs and make a selection with some confidence that your selection will do a good job for you 

[astronomynut]

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
 

[RikM]

The Astronomik UHC is a fantastic filter isn't it

The OIII is similar in many respects but offers a bit more contrast and is better than the UHC on some objects. Having played with a few filters now, I can totally see why the Astronomik OIII is a good single filter option. That said, I am glad I have both of them and the UHC is my favourite.

[timwetherell]

That said, I am glad I have both of them and the UHC is my favourite.

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

[Paul73]

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