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Gino Arcari

UHC or OIII for visual use?

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I'm thinking about buying a filter to improve the contrast on DSO's in my new 12". The question is, is there really a big difference between the UHC filters (baader, SW, etc) and the OIII filters? Will the OIII limit me to a certain amount of objects such as M27 and the veil? Thanks! :)

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UHC and OIII filters work in different ways to each other. Simply put;

UHC enhances the already visible (M42 etc)

OIII makes the invisible,visible (Veil,Rosette etc)

UHC works on more targets (or i should say that there are more targets for it to work on), so would be the better investment. I have both,which are SW branded. I find they work very good. The Castell UHC filter gets really good reviews.

Edited by LukeSkywatcher
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For visual use, I see no obvious disadvantage in using the Baader UHC-S
filter.  It "lets in" BOTH H-Alpha and O(III) +  H-Beta light from nebulae. 
At the same time blocks typical light pollution. For more detailed opinion: :)

http://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/ 

Edited by Macavity
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11 minutes ago, LukeSkywatcher said:

UHC and OIII filters work in different ways to each other. Simply put;

UHC enhances the already visible (M42 etc)

OIII makes the invisible,visible (Veil,Rosette etc)

UHC works on more targets (or i should say that there are more targets for it to work on), so would be the better investment. 

Cheers Paul, I think the UHC is probably the best bet for me, any brand UHC that you recommend?

 

7 minutes ago, Macavity said:

For visual use, I see no obvious disadvantage in using the Baader UHC-S
filter.  It "lets in" BOTH H-Alpha and O(III) +  H-Beta light from nebulae. 
At the same time blocks typical light pollution. For more detailed opinion: :)

http://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/ 

Thanks for the link Chris! That's exactly what I was looking for, so I can see what filter would be best on each object.

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For me the O-III makes the biggest impact on objects so is invaluable. A UHC type is a little more subtle but is still nice to have. I use both in my scopes from 4" to 12" in aperture. My O-III is the excellent Lumicon and the UHC is the Omega DGM NBP filter, also very good indeed. They are both in the 2" fitting.

 

 

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I think it may depend a little on you local LP and your preferred targets. Personally, in my mag 4.8 suburban skies I never saw much benefit from a UHC filter, but my OIII was a frequent flier in both 80-120mm refractory and a 10 inch dob. Could easily see the Veil, Rosette, Helix and North America nebula with the OIII, even in the smaller refractory whereas the UHC didn't help much at all on these targets. I'd definitely recommend the OIII as the first filter to have in your box of tricks.

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I always tend to assume UHC means H-Alpha red  + O(III) green/blue
Interesting to note Skywatcher's UHC is apparently an O(III) type filter?

http://ca.skywatcher.com/_english/03_accessories/02_detail.php?sid=232

In fairness, I suspect that I cannot SEE much in the H-Alpha range! But,
should you aspire to try such things protographically, with DSLR etc. ;)

Edited by Macavity
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I took the plunge on an Astronomiks O-III first, and was so impressed that subsequently I saved up and added a UHC in due course.  Both are worth it imho: the O-III is the one I use the most for the planetary nebs I observe.

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First buy the Astronomik UHC...

...good quality filter, works on a wide range of objects and gives a much more 'pleasing' view than the harsh OIII.

Then buy the Astronomik OIII.

Have used many filters from various manufacturers.   These work well.

Cheers

Paul

Edited by clarkpm4242
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I too use the OIII and find it works great, I was a tad disappointed with the UHC but I guess that is was down to the aperture of my scope :happy8:

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I started out with the skywatcher UHC and O3, I found both useful and worthwhile. The UHC was probably better than the O3 which I found dimmed the stars to much.

When I had more money, I upgraded to Astronomik UHC and O3 and the difference is very visible.

it depends on your funds. I would say that skywatcher UHC was value for money.

i would say that Astronomik are expensive but they have 10 year guarantee and DO perform better.

you get what you pay for I am afraid to say :)

 

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For a couple of years I found that the Astronomik O-III was the onlyl deep sky filter that I needed. It's a really effective tool.

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I found that the astronomik O3 has no noticeable dimming of the stars that the Skywatcher version had. The view was beyond comparison as it makes a massive difference if you can still see and appreciate the star field within the same FOV as the nebulosity.

You can look on filters as a one-off purchase as you try to convince yourself that the Astronomik price is reasonable. Perhaps that's why they are call Astronomik?

 

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I think the price of a good O-III filter is reasonable considering the difference it makes on some objects. Over the years, the views I've had of the Veil Nebula using the Astronomik and now the Lumicon O-III filters are some ofthe most memorable of all my observing in 30 or so years. This fabulous object goes from something which is at best just hinted at (at worst invisible !) to a complex, multi-element set of DSO's which can be explored for ages. On good nights with my 12" scope the O-III filter in my back garden produces views very similar to these sketches below made with an 8" but in a desert environment. Stunning and well worth the "entry fee" I reckon :icon_biggrin:

 

Veil-nebula-sketch.jpg

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I concur on the Astronomik-Filters. You may find others for less £££, but it's all about bandwidth and what our eyes show you - and the Astronomik-Filters simply are better quality all around the marble.

Enjoy -

Dave

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Thanks for the help everyone, It's really made me think about what I should do..

I think I'll probably get the Astronomik UHC first and then maybe look at the OIII a bit later on, I have no problem with spending a bit more on a premium filter if they genuinely do make an improvement from the cheaper ones.

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Gino Arcari,

a good decision. While the O III filter will give you the best contrast on many objects (in detail mentioned above), it sometimes dims the stars a bit too much in my opinion. The UHC  then gives a more "natural" view of the star field around. I'm using them both for the same percentage of observing time, the UHC more at the smaller scopes. Up to now, I don't own a H beta filter, and do not miss it.

Go for a good quality filter, e.g. Lumicon, Astronomik, Thousand Oaks - it will serve you many years.  -- Clear Skies!

Stephan

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2 hours ago, Nyctimene said:

Gino Arcari,

a good decision. While the O III filter will give you the best contrast on many objects (in detail mentioned above), it sometimes dims the stars a bit too much in my opinion. The UHC  then gives a more "natural" view of the star field around. I'm using them both for the same percentage of observing time, the UHC more at the smaller scopes. Up to now, I don't own a H beta filter, and do not miss it.

Go for a good quality filter, e.g. Lumicon, Astronomik, Thousand Oaks - it will serve you many years.  -- Clear Skies!

Stephan

Fair points from Stephan but the Astronomik O-III does not dim the surrounding stars as much as most other O-III filters because it's band pass width is a little more generous. I found it worked very well even with an 80mm scope and showed plenty of background stars.

UHC and O-III filters don't all use exactly the same prescription with regard to what they admit so it's worth doing a bit of research to see what a particular filter might do for you by comparing the band pass data most brands provide.

Edited by John
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I just purchased a NPB 1.25" filter which will go head to head with a VG Lumicon UHC.  Should be interesting.

I'm in the OIII first camp though, the extra contrast can really help out and espc from less than dark skies. There are lots of nebs seen with the OIII and is it THE filter for the Veil neb (IMHO) even though I use both the UHC and OIII on it.

Regardless of the filter match it to an appropriate eyepiece focal length for your scope and go observing- Gemini offers some nice objects for either filter.

To the OP- eagerly waiting reports!

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Problems with 'dimming-down' and image (view) is one reason I suggest the Astronomik over such possibles as the Baader.

Here's a bandwidth that passes through a Baader OIII:

Baader OIII spectra..jpg

Note the cut-off.

Now the Astronomik:

astronomik_oiii_trans.png

As you can see, more bandwidth is available through the Astronomik OIII filter that will meet your eye(s). Not sure about using for AP, but visually speaking, the Astronomik will give you a brighter image at the eyepiece.

Hope this helps give you something you can 'sink your teeth into.'

Dave

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Here is a Buyer's Guide to all the current visual-use nebula filters: http://www.cloudynights.com/topic/553293-2016-nebula-filter-buyers-guide-final-revised-version/?p=7661450

Some comments:

The 2 essential filters are the UHC (narrowband) type (transmits H-beta at 486nm and O-III lines at 493nm, 496nm and 501nm)

and

O-III filter (transmits 496nm and 501nm O-III lines, the 493nm line not being important)

The "Universal" filter is the UHC type since it pretty much catches the energy being emitted by nebulae in the wavelengths we can see at night.

The O-III filter enhances contrast more on objects emitting a lot more O-III than hydrogen energy--examples: planetary nebulae, supernova remnants, Wolf-Rayet excitation nebulae.

Both work best with larger exit pupils (say, below 10-12x/inch of aperture).

Narrower bandwidths enhance contrast more, but also dim the overall field.  Since our eye is more sensitive to contrast than brightness, narrow helps.

But a filter can be too narrow and either miss one of the spectral lines (as a photographic O-III does, passing only the 501nm O-III line), or too wide and with a reduced contrast.

Having a red transmission keeps the field brightness up a bit but doesn't reduce contrast much, so many filters also pass the deep red.  Some mind this, but many don't.

In terms of filter categories, I put them in several bins:

1) Notch filter--a very gentle filter which adds a *tiny* bit of contrast by removing a few light pollution wavelengths.  Work best in already dark skies.

2) CLS/Broadband filter--not much contrast enhancement, but can often be used at high powers, unlike the narrower filters.

3) UHC/Narrowband filter--with or without red wavelengths.  The universal filter, wider if you prefer more stars, narrower if you want more contrast.

4) O-III filters--with or without red wavelengths.  A high contrast filter for high excitation nebulae.  The widest ones pick up the 2 C2 lines and can be used as comet filters.

5) H-Beta filters--with or without red wavelengths.  The highest contrast possible for nebulae with primarily hydrogen emission, like IC434 behind the Horsehead, or NGC1499, etc.

I can't tell you which filter to buy, but the specs on the spreadsheet pretty much tell the story.  If a manufacturer doesn't even care to tell you how wide the filter is, or publish a spectral graph, they may not be very serious about their filters.

I currently own 29 different filters, and I have found at least one nebula for each that it enhances quite well.  I'd love to get rid of a few, but then......

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Happy buyer! These came today and I can truly say I'm well impressed with the build quality. I managed to give them a quick try in my light polluted back garden before the clouds came over.

Obviously, the first object I looked at was M42, I put the filter on the 28mm nirvana and WOW! Never have I seen the Orion nebula in that much detail before...I then tried the new ES 11mm with the filter and again, blew me away. I could clearly see the sharp nebula that runs down the left side of M42. I tried my bino viewers next but the clouds had covered Orion by the time I finished shortening the tube to achieve focus. 

At this point, only the north-eastern sky was clear so I quickly tried to find M97 and there it was, it was very faint but that's the first ever time I've been able to see it at all so I'm very happy. Just can't wait for the moon to go away and for the weather to clear so I can have a good full night of observing! 

20170213_220446.jpg

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Excellent items !

When you get a chance try a good O-III on M97 as well - with a 12" scope under a dark sky it really jumps out !

Edited by John
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Congratulations, that's a very good choice.:thumbsup:

BTW, you can get the scanned transmission curve for your filter by email them the series number , if you're interested i.e.

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