UHC Filter comparison

[Merlin66]

I set up the spectroscope with a 600 lpm grating with a solar spectra to compare the "blocking" of some well known UHC filters......... I was surprised by the results.

The Lumincon OIII has a VERY similar responce to a Meade 4000 Narrowband filter
The Baader UHC-S is almost identical to the Meade 4000 Broadband filter.

I should be able to document the results next weekend and can now offer to "test" any other filters the group may have.

[Don Pensack]

It's long been known the Baader (aka Celestron) filter had a broader passband (pun intended). Here are some sites with test results of different filters:
http://www.astrosurf.org/buil/filters/curves.htm
http://www.astroamateur.de/filter/
http://www.sas.org.au/filters.htm
http://home.freeuk.com/m.gavin/grism2.htm
A lot of info there.
An odd bit of info on Lumicon:
bandwidth:
UHC-24nm
OIII-11nm
HBeta-9nm
Don Pensack

[JohnH]

OK, so I think I want a UHC filter and my birthday is not far off - to enhance contrast and reduce the impact of light pollution and sky glow so that I can both view and image nebulae better. But which one to get?

I am after 2" model but now confused as to the best value - Baader, Lumicon, Meade, another make?

Can you help me choose or, better yet, sell me yours if you do not need it ! (lol)

[Merlin66]

For general UHC requirement, I'd go for the Baader UHC-S or a Meade 4000 Broadband, which ever gave the better price. My filters are only 1 1/4"

[matt]

Why wouldn't you go for one of these?

http://www.optcorp.com/product.aspx?pid=105-156-823-832-6644

[Merlin66]

I didn't have one to test so can't comment.

[Don Pensack]

A true UHC filter will broadcast the passband containing the 486nm line of Hydrogen Beta and the two O-III lines at 496 and 501nm and not much more. Ideally, these 3 lines should be broadcast at 90% strength or higher.
The filter should broadcast those frequencies and have a steep cutoff outside of them.
The UHC filters with a somewhat too-broad passband are Celestron, Astronomik, and Baader. The UHC filters with a normal passband are Meade, Lumicon, Orion. A UHC filter with a narrower than normal passband (but still adequate) is the DGM NPB. But that's only 7 of the 20 brands of them available.

Here are some links with tests to help compare them:
http://www.astrosurf.org/buil/filters/curves.htm
http://www.astroamateur.de/filter/
http://home.freeuk.com/m.gavin/grism2.htm
http://www.sas.org.au/filters.htm

And here are some links with good information about filters and their uses:
http://pages.sbcglobal.net/raycash/filters.htm
http://www.cloudynights.com/item.php?item_id=387
http://www.cloudynights.com/item.php?item_id=63&pr=2x9x42
http://www.cloudynights.com/ubbthreads/showflat.php?Cat=0&Board=beginners&Number=651806&fpart=1&PHPSESSID=

And here's a link to a buyer's guide to all nebula filters on the market (go down the page to the guide to filters):
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/198667/page/0/view/collapsed/sb/5/o/all/fpart/1

Memorize all the information. There will be a test.:lol:
Seriously, I post all this so all who read it can link to the sites mentioned and learn about nebular filters, what they do, how they work, and how they are different.

Don Pensack

[TidaLpHasE]

:)Another link that i have had for a while, a good comparison between different types.http://www.samirkharusi.net/filters.html

[astro_nutt]

Hi everyone,
I have recently brought an Astronomik UHC-E filter which has simliar properties to the Lumicon UHC with the addition of Ha..(which makes them a cheaper prospect than the UHC by itself)..it works quite well in my 10 inch dob at low magnification!!!...and thanks everyone for the wealth of information!
Cheers!

[dpastern]

Sorry to resurrect and old thread - I've just purchased one of these myself (waiting for it to be delivered, hopefully tomorrow so I can test it on the weekend if I get clear skies!!!). Anyone else using one of these?

Dave

[ausastronomer]

That's pretty subjective Don. It's a bit like saying the correct thickness ratio for a newtonian primary mirror should be 1/6 because thats what Isaac Newton said it should be 340 years ago when they were made from entirely different materials.

Similarly, filter technology has changed dramatically in recent years. I own the Astronomiks UHC, the Lumicon UHC and the DGM Optics NPB filters and they all do different things on different targets due to their slightly different bandpass characteristics. Over a wide variety of targets each of the three filters can outperform the other two on several different targets. To say the Astronomiks isn't a true or good UHC filter is inaccurate because it works within its design parameters (which is wider than some others, with the H-Alpha pass as well) and works well on certain targets

Cheers,
John B