Let's talk filters

[Don Pensack]

7 hours ago, Mark at Beaufort said:

The short answer is No. I have had various other UHC filters - Skywatcher, Sky's the Limit and Baader UHC-S but found that the Lumicon and TeleVue gave better contrast. There has been a great deal of debate on Lumicon filters because the company was originally started in Livermore, CA then was sold out and the next batch was not as good. Since then stage 3 has provided a new series which I understand is good. Perhaps @Don Pensackin the States can confirm this situation.

Lumicon has had 4 owners and there have been at least 5 different makers of the filters.

The first owner was 1979-2001

The second owner was 2001-2012  The filters were VERY high quality, but expensive.

The 3rd owner was 2012-2016  She got bitten by an unscrupulous filter provider

The 4th owner is 2016 till now.  At first, he was selling off old stock, but moved into another provider in 2018.  They were relabeled "Gen.3" to differentiate.  I can see that.  Calling them Gen.9 would have been really confusing to customers. LOL.

 

The Baader UHC-S, by the way, is a misnomer.  It's a broadband filter of about a 62nm bandwidth.  it's one of the very best broadbands, but it's not a narrowband UHC-type filter.

Ditto the Astronomik UHC-E, 49nm bandwidth, which, though narrower than the UHC-S is more of a broadband than a narrowband UHC-type.  I'd call it a "medium bandwidth" filter.

 

This site allows you to superimpose any filters you want that have been tested:

https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8#

Note that all the filter graphs displayed are as they were tested in the lab, NOT what the manufacturer claims.  You can see he has tested a LOT of filters.

Edited June 10, 2020 by Don Pensack

[Stardaze]

6 hours ago, John said:

One way to get an idea how a filter might perform compared with another is to look at the band pass charts for them:

The above is a couple of years out of date now but it shows that there are differences in band pass width, cut-off profiles and maximum transmittance between brands. Where the profiles are relatively close, the visual impact will probably be undetectable but the larger differences do make a difference that can be seen.

Here are similar charts for a group of UHC filters with a bit more information to help interpret them:

 

I have seen profiles for O-III filters which make them practically UHC status and likewise UHC's that are moving into the broadband territory.

Apologies if the above is "data overload" on filters

It's not too much info John at all. I actually work within lighting to spectral wavelengths I understand. 

[Mark at Beaufort]

2 hours ago, Don Pensack said:

Lumicon has had 4 owners and there have been at least 5 different makers of the filters.

The first owner was 1979-2001

The second owner was 2001-2012  The filters were VERY high quality, but expensive.

The 3rd owner was 2012-2016  She got bitten by an unscrupulous filter provider

The 4th owner is 2016 till now.  At first, he was selling off old stock, but moved into another provider in 2018.  They were relabeled "Gen.3" to differentiate.  I can see that.  Calling them Gen.9 would have been really confusing to customers. LOL.

 

The Baader UHC-S, by the way, is a misnomer.  It's a broadband filter of about a 62nm bandwidth.  it's one of the very best broadbands, but it's not a narrowband UHC-type filter.

Ditto the Astronomik UHC-E, 49nm bandwidth, which, though narrower than the UHC-S is more of a broadband than a narrowband UHC-type.  I'd call it a "medium bandwidth" filter.

 

This site allows you to superimpose any filters you want that have been tested:

https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8#

Note that all the filter graphs displayed are as they were tested in the lab, NOT what the manufacturer claims.  You can see he has tested a LOT of filters.

Thanks Don for that historical information. I am not sure of the date of my Lumicon UHC although I know it was manufactured in Livermore CA. My Son lives in Livermore CA and I was a guest of the Tri valley Stargazers and was able to use the 17.5 inch Newt donated by Dr Jack Marling the original owner and founder of Lumicon.

[Louis D]

Has anyone tried those new dual, tri, and quad band nebula filters intended for single shot astrophotography visually?  They're pretty expensive, but if they work under light polluted skies, they might be worth it.

[bomberbaz]

On 09/06/2020 at 21:34, Don Pensack said:

 

Now, broader filters, like a broadband, can be used at a bit higher magnifications without dimming the objects quite as much--maybe up to 12x-13x/inch of aperture.

But their effects are, at best, somewhat subtle, and only improve contrast a tiny bit.

Hello Don, love your contributions to these threads, you bring a lot of science and knowledge to them.

I have a UHC-S dating back to 2015 I think although I am not sure. I note from your testing you stated UHC-S post 2017.  Regarding my UHC-S I don't find the results subtle at all, to me the differences were quite noticeable  with good contrast.

I have also used it on Jupiter as it really helps the whole planet and especially the  GRS stand out.

Do you know if the post 2016 models of a different design by any chance. 

 

[John]

It was a Baader UHC-S filter that 1st showed me the Veil Nebula, with a 100mm refractor. That was around 10 years ago so I think the UHC-S was quite a new product back then.

I got it because I read (from Baader) that it was designed to have a more generous band pass so would be suitable for smaller aperture scopes. As I moved up in aperture from 100mm I found that "proper" UHC's and O-III's were more effective than the UHC-S. Which is sort of what I expected.

Nothing wrong with the UHC-S though. It is good quality and does what it is designed to do.

 

[Don Pensack]

2 hours ago, bomberbaz said:

Hello Don, love your contributions to these threads, you bring a lot of science and knowledge to them.

I have a UHC-S dating back to 2015 I think although I am not sure. I note from your testing you stated UHC-S post 2017.  Regarding my UHC-S I don't find the results subtle at all, to me the differences were quite noticeable  with good contrast.

I have also used it on Jupiter as it really helps the whole planet and especially the  GRS stand out.

Do you know if the post 2016 models of a different design by any chance. 

 

I don't know if they changed it, and I regard it as one of the best, if not THE best broadband filter.

I think the tune up of contrast is there, and it is noticeable, but I always have to add the caveat that it is subtle because so many are led to believe nebula filters provide a huge improvement,

and they will be disappointed if using a filter this wide.  Additionally, in high light pollution, often the case with city dwellers, the broader the bandwidth, the more the internal scattered light in the filter.

Using an Astronomik CLS filter (99nm bandwidth in the blue-green and wider in the red) here in Los Angeles made the view WORSE than the view without the filter in place.  Light scatter was horrendous.

So I think that a broadband filter has to have certain caveats attached to it.  I think they work their best at sites where the sky is already quite dark and many/most objects need no filter at all, and the presence of the broadband 

just turns up the contrast a bit, making things a bit more visible than without the filter, but not dimming the stars quite so much as in the narrowband filters.

I also cannot know how sensitive an observer is to small changes in contrast.  A narrowband drops the brightness of the background sky by around 2.3-2.5 magnitudes and an O-III filter around 3 magnitudes.  That is not subtle.

Here is a simulation of various nebula filters:

https://www.cloudynights.com/topic/385867-filter-simulator/?p=4939179

I wouldn't call the broadband filter improvement subtle, but I think most would compared to the narrowband.

[this nebulae doesn't respond well to H-ß, which explains that simulation.]

There are objects where the broadband shines, though, like NGC7023, IC405, or Sh2-155.

And, quite certainly, if used in appropriate circumstances, it will be much better than no filter at all.  

[bomberbaz]

I recently purchased a astronomik uhc filter and was very surprised at the increase (should that be decrease) in filter bandpass effectiveness.  However I have only used in briefly on the owl nebula as I was at a new dark site (which turned out not that dark) so I wasn't actually there testing the filter.

I will try to give all my filters, uhc, hb, 03 (all astronomik)  and uhc-s a thorough workout next time I have a chance.

However I am still waiting opportunity to test out my 24mm/65 apm against a range of other eyepieces though. I think the latter will be the first to get a workout, the apm looks beautiful.

Edited June 12, 2020 by bomberbaz

[John]

Try a good O-III on the Owl or the Veil and the difference over a UHC is quite noticable.

[bomberbaz]

On 10/06/2020 at 16:30, Don Pensack said:

 

This site allows you to superimpose any filters you want that have been tested:

https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8#

Note that all the filter graphs displayed are as they were tested in the lab, NOT what the manufacturer claims.  You can see he has tested a LOT of filters.

Great website that Don. 

I notice the astronomik changing versions of UHC but when compared the bandwidth remains pretty much the same.

However the same comparison with the already tighter tv nebustar shows the the v2 one tightens up even further over the v1. Not reading anything into that, just curious. 

Regarding the ES O-III and HB they appear to have some bandwidth drift which in the case of the O-III is quite significant on the face of the lab tests. It would be very interesting to run a comparison on relevant bandwidth appropriate DSO's. 

[Stardaze]

Glad we started this thread, it's been very informative 😃

[vineyard]

On 10/06/2020 at 16:30, Don Pensack said:

This site allows you to superimpose any filters you want that have been tested:

https://searchlight.semrock.com/?sid=a08a1af9-84ee-49d2-959d-153d7e7c0eb8#

Note that all the filter graphs displayed are as they were tested in the lab, NOT what the manufacturer claims.  You can see he has tested a LOT of filters.

I'd echo others comments Don - your contributions are always incredibly helpful.  That's a great link (already bookmarked).  As per @bomberbaz I also noticed the multiple versions of Astronomik UHC (and your caveat re post-2017).

Do you know what the differences are between them - the curves don't look that dissimilar (although perhaps the marginal change at the eyeball is quite dramatic?).  I've got an old Astronomik UHC - no idea whether its type 1, 2 or 3 as per the semrock website, but I've emailed Astronomik w the serial number to find out (I suspect mine is very old - the serial number begins with 002003... which suggests 17 yrs ago...maybe filters are like fine wine & get better w age? 🤞🏾😂).

Stay safe all.

[Louis D]

3 hours ago, vineyard said:

maybe filters are like fine wine & get better w age?

Lumicon had an issue with some of their filters oxidizing from the outside in.  There are tests of H-Beta and O-III oxidized filters on the SearchLight website showing how much they have shifted off of their emission lines.

[bingevader]

10 hours ago, bomberbaz said:

Regarding the ES O-III and HB they appear to have some bandwidth drift which in the case of the O-III is quite significant on the face of the lab tests. It would be very interesting to run a comparison on relevant bandwidth appropriate DSO's. 

I'd be interested in the results. Will be looking to get an O-lll at some point in the future. Would be the ES or the Optolong, but noticed the shift in the ES too!

[John]

10 hours ago, vineyard said:

..  I've got an old Astronomik UHC - no idea whether its type 1, 2 or 3 as per the semrock website, but I've emailed Astronomik w the serial number to find out (I suspect mine is very old - the serial number begins with 002003... which suggests 17 yrs ago...maybe filters are like fine wine & get better w age? 🤞🏾😂).

 

The serial number on my Astronomik O-III starts 003002 - perhaps it's from the future ?

[vineyard]

1 minute ago, John said:

The serial number on my Astronomik O-III starts 003002 - perhaps it's from the future ?

You've been rumbled John.  Its like that book of all future sports results that Marty McFly had in Back to the Future...

Also, crikey that photo & oxidisation!  Is that from not being stored properly or just random happenstance?

Btw, I heard back from Astronomik (I'd emailed them my UHC filter serial number as the box showed 95.8% transmission on the label vs 97% cited on their website so I was curious).  They were v prompt in replying (one of the many reasons why I stick to Astronomik) and explained that 97% is a typical transmission rate, and that they find from tests that differences of up to 3% are barely visible.

They also told me that my filter serial number had a FWHM of 22.2nm vs a typical figure of 27nm so will give 18% less background light.  And that this narrower FWHM was also a factor in the transmission rate difference?

Anyway, net-net I think they test the combined specs of each filter & decide whether it can be sold or not - which is good enough for me

Stay safe all!

[John]

This is my Lumicon 2 inch O-III. I don't know when it dates from exactly - perhaps 6-7 years back ?. It's a cracking performer

[Don Pensack]

12 hours ago, bomberbaz said:

Great website that Don. 

I notice the astronomik changing versions of UHC but when compared the bandwidth remains pretty much the same.

However the same comparison with the already tighter tv nebustar shows the the v2 one tightens up even further over the v1. Not reading anything into that, just curious. 

Regarding the ES O-III and HB they appear to have some bandwidth drift which in the case of the O-III is quite significant on the face of the lab tests. It would be very interesting to run a comparison on relevant bandwidth appropriate DSO's. 

Original Nebustar was made by a different company than the Nebustar-II.  The original was a lot wider.

The results on the ES filters shows the effect of making things very cheaply without any QC.

The #1 problem with the inexpensive filters isn't the too-wide bandwidth, it's inconsistency from filter to filter.

Unless you test it, you don't know what you have.

 

This thread should be mandatory reading for those who want to know about filters:

https://www.cloudynights.com/topic/527199-spectroscopic-analysis-comparison-of-nebula-filters/?hl=%2Bspectroscopic

Edited June 12, 2020 by Don Pensack

[Stardaze]

9 hours ago, Don Pensack said:

Original Nebustar was made by a different company than the Nebustar-II.  The original was a lot wider.

The results on the ES filters shows the effect of making things very cheaply without any QC.

The #1 problem with the inexpensive filters isn't the too-wide bandwidth, it's inconsistency from filter to filter.

Unless you test it, you don't know what you have.

 

This thread should be mandatory reading for those who want to know about filters:

https://www.cloudynights.com/topic/527199-spectroscopic-analysis-comparison-of-nebula-filters/?hl=%2Bspectroscopic

That’s a great link, thanks. Also backs up caution when buying old filters. How common is oxidisation/degradation of the coatings over time in your opinion @Don Pensack?

[bingevader]

18 hours ago, Don Pensack said:

Original Nebustar was made by a different company than the Nebustar-II.  The original was a lot wider.

The results on the ES filters shows the effect of making things very cheaply without any QC.

The #1 problem with the inexpensive filters isn't the too-wide bandwidth, it's inconsistency from filter to filter.

Unless you test it, you don't know what you have.

I got lucky with my ES UHC then!

Hopefully the same will be true of the O-lll, when I get one, because it's only ever going to be one of the inexpensive options.

[RT65CB-SWL]

I don't normally use filters, except for a variable polarising and the Baader Neodymium.

Sometime last year [2019] another SGL'er was selling the Explore Scientific UHC & O-lll and so I decided to take the plunge/bite the bullet, so I purchased them. So far I have had no qualms about them and they do seem to make a difference in teasing out detail. I did read here on SGL in another post/topic and other forums, online vendors, etc., that cheaper UHC's and O-III's are/were best avoided. 

Personally, I think the Explore Scientific CLS is slightly better than the Baader Contrast Booster.

[Louis D]

I have a sub-$20 Zhumell OIII filter which acts more like a light pollution filter than a true OIII filter like my 90s vintage Lumicon.  Price does make a difference.

[Don Pensack]

14 hours ago, Stardaze said:

That’s a great link, thanks. Also backs up caution when buying old filters. How common is oxidisation/degradation of the coatings over time in your opinion @Don Pensack?

Uncommon on filters made since 2005.

[Don Pensack]

4 hours ago, Philip R said:

I don't normally use filters, except for a variable polarising and the Baader Neodymium.

Sometime last year [2019] another SGL'er was selling the Explore Scientific UHC & O-lll and so I decided to take the plunge/bite the bullet, so I purchased them. So far I have had no qualms about them and they do seem to make a difference in teasing out detail. I did read here on SGL in another post/topic and other forums, online vendors, etc., that cheaper UHC's and O-III's are/were best avoided. 

Personally, I think the Explore Scientific CLS is slightly better than the Baader Contrast Booster.

My sample of the Baader UHC-s has a 62nm bandwidth in the blue-green.

bandwidth FWHM	H-B line	O-III (1)	O-III (2)	Ha	low wavelength	High wavelength
62	93.3	94.7	95.0	87.1	464	526

 

Comparing with my ES CLS:

FWHM        H-ß      O-III   O-III   H-α    low         High

75               92.1      95.2   94.0    89.9   451         526

Both are decent broadband filters.

The Baader UHC-S has the edge for visual contrast on nebulae simply due to a narrower bandwidth.

The CLS and Baader differ in their long wavelength cutoffs, though.

The Baader cuts off at 675nm, with almost no output at all up to 1000nm., while the ES CLS cuts off at 756nm, with a broad bump centered on 950nm.

I'd say that the ES CLS would be better for imaging because of that.

 

 

[Stardaze]

Who are Orion? There's a couple of obscure vendors here in the UK, but none of the mainstream suppliers seem to distribute? Are they not as they once were?

The other thing that I'm not finding an understanding with is the H-Alpha line as, from the theory I knew, it falls outside of the human eye's sensitivity range. Just looking at the Astronomik UHC filter the second emission line starts around 630nm and extends well beyond 750nm?

Edited June 14, 2020 by Stardaze