Tell me about LP FILTERS please

[GeezerGazer]

What's the truth about light pollution filters? I've seen everything from great to negligible about their effectiveness. I live just on the northeast side of the Dallas/Ft.Worth metroplex, so I'd welcome input from anyone that has similar seeing conditions. I know that there is no substitute for dark skies, but are there effective LP solutions that are worth the money?

[Moonshane]

I have poor skies too but never use L.P. filters. That said they can be effective on emission nebulae and some planetary nebulae. They are no use really on galaxies as such broadband filters slightly filter out  all wavelengths of light thus reducing the galaxy's light too.

I have one but plan to use it as a planetary filter on Mars.

I tend to increase magnification to increase contrast where necessary. Getting into the darkest spot in your garden out of direct local light really helps more.

[Stu]

Depends what we are defining as LP filters I guess. I don't use broadband LP filters, but do use OIII and UHC filters, very effective at bringing out emission nebulae.

[spaceman_spiff]

I use a Baader UHC-S filter. It helps reduce LP sky brightness, increase contrast on emission nebulae and in my opinion, helps bring out star colours.

[TareqPhoto]

Visual or imaging?

[GeezerGazer]

Visual, TereqPhoto

[Cosmic Geoff]

It is necessary to understand how the filters work. Light pollution filters were introduced to combat light pollution from discharge lamp street lighting, which emits light in a series of narrow spectral bands. In principle, at least, this can be counteracted by using a filter which blocks those lines and passes the rest. But such filters are impotent against white LED lighting, which emits a continuous spectrum.

The other approach is to use OIII and UHC filters, which pass line emissions at certain wavelengths, and block the rest. The effect is to make line-emitting objects like nebulae appear brighter relative to the background.

[Mak the Night]

Where I live and observe from it's quite dark, but occasionally I find a basic contrast filter aka 'light pollution' filter can work quite well if the conditions aren't good. Often when there appears to be a lot of water vapour in the air. I won't normally discuss filters on this forum because of the trolling but below is a copy/paste of some reviews I made of some relatively inexpensive 'light pollution' filters on a forum where these matters can be discussed sensibly. Personally, it all depends what type of scope I'm using that dictates the filter. With my refractors, a Baader Neodymium filter would be my first choice. For some reason I find that a basic contrast filter can work well for low power viewing with a scope that has a long focal length (like a Maksutov).

Although sold as the Solomark ‘Moon & Skyglow Filter’ there is no manufacturer or distributor’s name on the filter housing itself. It seems fairly well made, with an aluminium housing, male & female threads, and decent quality glass although I see no evidence of coatings. With its distinctive serrated crown on one side of the housing it is reminiscent of GSO filters, although I don't think it is actually made by GSO. It is supplied in a nice but cheap plastic case with a foam insert. This was a bit tricky for me to open at first, but is relatively easy when you get the knack. In preliminary daylight testing it does tend to work quite well as a contrast filter, although, compared directly with a Baader Neodymium filter the image was distinctly darker. I think this background darkening effect is basically what these sort of inexpensive filters do best.

A lot of street lighting is now LED, and not produced by low pressure yellow sodium vapour lamps, so I don't know the relevance or efficacy of blocking these particular wavelengths (589.0 and 589.6 nm) now. I do think that the contrast change for DSO viewing would be good though. I'm also pretty sure this will also be an effective contrast filter for lunar viewing. Although I don't think it particularly acts exactly like a neodymium filter and wouldn't expect it to. I discovered that the Solomark threaded onto all of my diagonals (Celestron, Orion, GSO, Omegon, Antares), except for a William Optics 90° Amici prism, where it threaded for a few turns then seemed to get stuck. Although it did thread onto a 45° William Optics Amici prism diagonal. I'm guessing the thread isn't the standard M28.5 x 0.6 like Baader and GSO are. It also threaded quite happily onto Celestron, Sky-Watcher, Meade, Bresser, Vixen and TeleVue eyepieces. I had threading difficulties with one or two Japanese Abbe orthoscopics (Kasai, Astro Hutech) but from previous experience I more or less expected that.

After some examination of my own Solomark 'Moon & Skyglow' filter and comparing it with the portrayals of it on Amazon and elsewhere (which differ slightly to what mine actually looks like) and other similar filter representations, I'm pretty convinced it has the same origins as the Sky-Watcher 'Light Pollution Filter' and others. I'd wager they all come from the same factory or at least the housings do. The Solomark was roughly half to a third the price of what the Sky-Watcher retails at where I live. It would be interesting to know how similar, if not identical, these filters are as there is some discrepancy in the individual prices. Basically, the Solomark is an inexpensive, but decently made, contrast filter.

As far as I can determine SOLOMARK is a trademark of Yuyao Qihang Optical Instrument Co., Ltd. Yuyao City, Zhejiang Province, China. It could just be that Synta acquire a lot of their filters from Yuyao Qihang Optical and rebrand them, or more likely they are custom made to order. In which case the Sky-Watcher Light Pollution Filter is exactly the same as the Solomark Moon & Skyglow Filter and may explain why they look so similar.

The TS Optics UCF 1 or ‘Universal Contrast Filter 1.25" - for Moon & Planets’ retails for slightly more than the Solomark Light Pollution and Crystalview Moon filters and is approximately twice the price of the Solomark Moon & Skyglow filter. 

Interestingly the box and package it arrived in were identical to the Solomark Light Pollution and Crystalview Moon filters. However, it doesn’t resemble either and the housing is slightly taller and differs in design slightly. 

The TS Optics site claims: ‘A modest allround (sic) filter also for nebulae and non-astronomical use’

The UCF 1 has polished and parallel surfaces, anti reflective coating, homogeneous glass and a filter thread on both sides. I’m assuming the threads are M28.5 x 0.6 as they appear to thread onto everything I tried it with.

It seems fairly well made for what it cost (23.50 euro) and was effective as an overall contrast filter when sweeping starfields using magnifications between 36x and 75x. In my opinion, in conditions of below average transparency, it often worked as a better overall contrast filter when observing Jupiter than a Baader Neodymium did as it darkened the background sky more effectively. 

It also seemed to handle a magnification of 225x (130mm, f/6.9 Newtonian) easily with no discernible internal reflections threaded directly onto a 4mm TS Optics Planetary HR eyepiece.The Jovian equatorial zones and bands, particularly the southern temperate zones were easier to discern when the UCF 1 was deployed.

The aperture size of the glass seems slightly wider than any of the Solomark filters. It also differs slightly from the rebadged GSO Wratten coloured filters TS Optics sell.

I hope this is some help.

 

 

[Stu]

Useful reviews @Mak the Night. You shouldn't find any trolling on SGL so feel free to post.

Does a size by side test holding the SoloMarl up to white light show any difference to the Baader Neodymium?

[Paul67]

I can't speak with direct knowledge of any of the filters but I did perform quite a bit of research. My conclusions were UHC and OIII filters for a fair amount of nebula and a pair of widefield binos such as the Vixen SG 2.1x42 Widefield Binoculars to scan the sky's and find stuff you ordinarily wouldn't pick up naked eye when looking for targets. Not cheap but I think could combat quite a few problems when you have light polluted sky's.

[Mak the Night]

I'm fairly sure Lumicon developed the first UHC (Ultra High Contrast) 'narrowband' filters. Narrowband filters normally transmit between 484 and 506 nanometres. In my experience narrowband filters can be of limited use on many emission nebulae, where a broadband filter can reveal more detail. This is also related to aperture and exit pupil. I found that a Lumicon UHC was of limited use on a reflecting telescope under 15 centimetres when used to view emission nebulae like M42 (Orion Nebula), M8 (Lagoon Nebula) and M20 (Trifid Nebula), the latter technically being a combination of emission and reflection nebulae.  But a 'broadband filter' often referred to as an LPR (Light Pollution Reduction) filter which also passes H-alpha, H-beta, and O III can give better and more detailed results. Conditions will always dictate whether a filter has any efficacy or not anyway. Furthermore, manufacturers and distributors use various terms to describe their respective products, many which can almost be meaningless.

The Orion SkyGlow and Baader UHC-S are technically broadband filters.

The Astronomik UHC-E is considered a wide narrowband.

As opposed to the narrowband Orion UltraBlock.

The Lumicon OIII is considered a narrowband,

yet the Explore Scientific OIII filters are aimed at smaller apertures and considered 'wide' narrowband by some. Much of it comes down to marketing. Much of it comes down to aperture size and exit pupil. YMMV.

 

Let the trolling commence ...

[Louis D]

I, too, have to deal with Texas skies near a large city.  I pretty much can't observe in any direction that lies above a nearby city except for solar system objects.  My eastern skies are best and don't benefit from light pollution filters.  I do have the Zhumell version of the Moon & Skyglow filter that I picked up cheap several years back, and I use it strictly to find comets in the western murk after sunset.  It gives just enough contrast to find them by scanning back and forth in the general area they should be located.  They still just look like a slightly lighter patch on the sky, so it's not very satisfying other than to check it off as having found it.

UHC and OIII filters are much more effective and are definitely worth the money if you can get Lumicon originals (before the recent change of ownership) or a couple of other high end suppliers.  I picked up a $16 Zhumell OIII for comparison.  Let's just say there is no comparison.  First off, it appears green rather than mirror-like like the Lumicon.  Second, it acts like a darker version of the M&S filter.  Perhaps it might be useful as a stronger lighter pollution filter, but not as nebula filter.

From Melissa, TX, I would try to observe in your eastern skies as well.  Once they pass the meridian, they will get progressively worse to observe, so look for new eastern targets at that point.

[Stu]

On 15/03/2018 at 00:59, Mak the Night said:

I'm fairly sure Lumicon developed the first UHC (Ultra High Contrast) 'narrowband' filters. Narrowband filters normally transmit between 484 and 506 nanometres. In my experience narrowband filters can be of limited use on many emission nebulae, where a broadband filter can reveal more detail. This is also related to aperture and exit pupil. I found that a Lumicon UHC was of limited use on a reflecting telescope under 15 centimetres when used to view emission nebulae like M42 (Orion Nebula), M8 (Lagoon Nebula) and M20 (Trifid Nebula), the latter technically being a combination of emission and reflection nebulae.  But a 'broadband filter' often referred to as an LPR (Light Pollution Reduction) filter which also passes H-alpha, H-beta, and O III can give better and more detailed results. Conditions will always dictate whether a filter has any efficacy or not anyway. Furthermore, manufacturers and distributors use various terms to describe their respective products, many which can almost be meaningless.

The Orion SkyGlow and Baader UHC-S are technically broadband filters.

The Astronomik UHC-E is considered a wide narrowband.

As opposed to the narrowband Orion UltraBlock.

The Lumicon OIII is considered a narrowband,

yet the Explore Scientific OIII filters are aimed at smaller apertures and considered 'wide' narrowband by some. Much of it comes down to marketing. Much of it comes down to aperture size and exit pupil. YMMV.

 

Let the trolling commence ...

@Mak the Night I am tiring a little of the trolling references, which you seem to consider for any comment which disagrees with your own opinion.

I find generally the opposite of your views. Narrowband filters like the Lumicon OIII and UHC can make the difference between an object like the Veil or NAN being visible or not, so for emission nebulae I would recommend them over a broadband filter. I have used them on a variety of scopes, from 60mm to 400mm aperture.  Much depends upon the sky conditions. With a small scope, they can darken the image too much unless you have good dark adaptation, so at a light polluted site a hood can help to cut out the glare, but results can still be mixed. Under a reasonably dark sky though (mag 20. something), narrowband filters, with a 4" scope and a low power eyepiece to give a big exit pupil can be wonderful. I am sure though at a properly dark site (>21.5 say) even filterless views are amazing.

M42 is an object in itself really, it provides wonderful views at many different magnifications and whether filtered or not, because it is as you say, both reflection and emission nebula. I think it best with perhaps something like a DGM NPB filter rather than OIII or UHC, but each filter brings out different elements.

[Mak the Night]

1 hour ago, Louis D said:

I, too, have to deal with Texas skies near a large city.  I pretty much can't observe in any direction that lies above a nearby city except for solar system objects.  My eastern skies are best and don't benefit from light pollution filters.  I do have the Zhumell version of the Moon & Skyglow filter that I picked up cheap several years back, and I use it strictly to find comets in the western murk after sunset.  It gives just enough contrast to find them by scanning back and forth in the general area they should be located.  They still just look like a slightly lighter patch on the sky, so it's not very satisfying other than to check it off as having found it.

UHC and OIII filters are much more effective and are definitely worth the money if you can get Lumicon originals (before the recent change of ownership) or a couple of other high end suppliers.  I picked up a $16 Zhumell OIII for comparison.  Let's just say there is no comparison.  First off, it appears green rather than mirror-like like the Lumicon.  Second, it acts like a darker version of the M&S filter.  Perhaps it might be useful as a stronger lighter pollution filter, but not as nebula filter.

From Melissa, TX, I would try to observe in your eastern skies as well.  Once they pass the meridian, they will get progressively worse to observe, so look for new eastern targets at that point.

I have an original Lumicon UHC, I'm not really sure what's happened with Lumicon now. I've heard they aren't what they were. Not long ago I directly compared a Lumicon UHC, an Orion UltraBlock, an Astronomik UHC-E, an Orion SkyGlow and a Baader UHC-S on The Orion Nebula.

The telescope was a 102mm SkyMax (Maksutov) and I used a variety of magnifications and eyepieces and mainly kept the exit pupil above 3mm. Eyepieces included a 40mm Plossl and 23mm and 25mm eyepieces equipped with  0.5x reducers effectively doubling their focal lengths.

The results were that the Orion SkyGlow and the Baader UHC-S showed the most detail with the SkyGlow being slightly more contrasted. The Lumicon probably had the best contrast but there was a slight but noticeable lack of detail compared to the broadband filters.

The Astronomik UHC-E was somewhat in the middle, which I more or less expected.

I can't speak for the trolls, and I'm not particularly interested in their opinion anyway, but these are the results I got with a four inch Mak. Things do change when you use refractors of around four inches though and they perform well with narrowband filters. In my experience reflecting scopes need at least a six inch aperture to use most narrowband filters at their maximum efficacy. Of course, YMMV.

[admin]

On 12/03/2018 at 10:35, Mak the Night said:

I won't normally discuss filters on this forum because of the trolling 

 

16 minutes ago, Mak the Night said:

I can't speak for the trolls, and I'm not particularly interested in their opinion anyway

An internet troll is someone who posts a deliberately provocative message to a forum with the intention of causing disruption and argument. 

Someone respectfully offering an alternate opinion is not trolling. 

HTH

[Mak the Night]

10 minutes ago, admin said:

 

An internet troll is someone who posts a deliberately provocative message to a forum with the intention of causing disruption and argument. 

Someone respectfully offering an alternate opinion is not trolling. 

HTH

I'm not the one arguing with an opinion. As I stated: YMMV. I don't care if someone disagrees with my opinion. That's what forums are for. I think you have to look who's causing the enmity here. 

There is trolling on this forum. But it isn't by me. I don't reply to (or feed) trolls.

[Stu]

42 minutes ago, Mak the Night said:

I have an original Lumicon UHC, I'm not really sure what's happened with Lumicon now. I've heard they aren't what they were. Not long ago I directly compared a Lumicon UHC, an Orion UltraBlock, an Astronomik UHC-E, an Orion SkyGlow and a Baader UHC-S on The Orion Nebula.

The telescope was a 102mm SkyMax (Maksutov) and I used a variety of magnifications and eyepieces and mainly kept the exit pupil above 3mm. Eyepieces included a 40mm Plossl and 23mm and 25mm eyepieces equipped with  0.5x reducers effectively doubling their focal lengths.

The results were that the Orion SkyGlow and the Baader UHC-S showed the most detail with the SkyGlow being slightly more contrasted. The Lumicon probably had the best contrast but there was a lack of detail compared to the broadband filters.

The Astronomik UHC-E was somewhat in the middle, which I more or less expected.

I can't speak for the trolls, and I'm not particularly interested in their opinion anyway, but these are the results I got with a four inch Mak. Things do change when you use refractors of around four inches though and they perform well with narrowband filters. In my experience reflecting scopes need at least a six inch aperture to use most narrowband filters at their maximum efficacy.

Maks are obviously a different case than refractors as they as a longer focal ratio and the exit pupils you achieve are smaller. That will obviously cause narrowband filters to be operating at the lower end of their range and will explain the results you are getting. It is not the reflecting nature of the scope, but the focal ratios that are the issue. An f4 Newt would likely perform well with a narrowband filter.

[Stu]

36 minutes ago, Mak the Night said:

I think you have to look who's causing the enmity here. 

There is trolling on this forum. But it isn't by me. I don't reply to (or feed) trolls.

There is no emnity here @Mak the Night, only genuine posts which are asking valid questions.

[michael.h.f.wilkinson]

I have used a UHC filter (narrow-band) to great effect on emission nebula such as the Veil, NGC 7000 and the Pelican in an 80mm refractor. Similar results can be had with a 115mm F/4.3 rich-field Newtonian. As stated by Stu, exit pupil is more of an issue than aperture, or whether the scope is a reflector, refractor or catadioptric

[Louis D]

1 hour ago, Mak the Night said:

The results were that the Orion SkyGlow and the Baader UHC-S showed the most detail with the SkyGlow being slightly more contrasted. The Lumicon probably had the best contrast but there was a slight but noticeable lack of detail compared to the broadband filters.

Having just the one Lumicon UHC of 1990s vintage, I can't make any comparisons as you have against other UHCs.  It's worked well enough for me that I haven't felt the need to buy any others for 20 years.  I don't use filters often enough to justify the additional costs of having nearly redundant options.  I might change my mind if good UHCs came down to the $20 range.  My experience with the Zhumell OIII for $16 tells me that good nebula filters don't come cheap.

The one thing about these interference filters that I don't like is how it makes bright stars a weird red/green (IIRC) like as if you're looking through a pair of 3D glasses with the blue side replaced with green.  While they make the Orion nebula stand out better, the Trapezium looks incredibly odd.  I can only take the effect for so long before reverting back to no filtration.  On the Veil where there aren't many bright stars, it's not very noticeable.  The M&S filters don't seem to have this dramatic effect.  They also don't have a mirror-like finish, so they don't appear to be interference type filters.

[Mak the Night]

1 hour ago, michael.h.f.wilkinson said:

I have used a UHC filter (narrow-band) to great effect on emission nebula such as the Veil, NGC 7000 and the Pelican in an 80mm refractor. Similar results can be had with a 115mm F/4.3 rich-field Newtonian. As stated by Stu, exit pupil is more of an issue than aperture, or whether the scope is a reflector, refractor or catadioptric

Yes, like I stated way earlier, conditions, aperture and exit pupil all contribute to whether a particular filter works or not. I find broadband filters can often be more effective on smaller apertures. I can effectively use narrowband filters on an f/6, 150mm Newtonian, yet this isn't always the case on an f/6.9, 130mm Newtonian. I've had similar results to you with an 80mm f'5 refractor. Conditions dictate filter usefulness in my experience.

[Stub Mandrel]

My experience of LP filters is pretty basic and heavily biased towards imaging.

I 'supposedly' have Bortle 5 skies but even under very good conditions I struggle to see the milky way except for straight up. I have some industrial sites and dual carriageway which both create low down LP and being not too far from the trent (about 1/2 mile) we get a lot of low mist which can ruin conditions even when you see stars straight up.

The good thing is that it's mostly low-pressure sodium and some of the dual carriageway lights have been replaced with better units that send less light in the wrong direction.

Someone on SGL suggested a cheap 'moon and skyglow' filter - this made a big difference to imaging with my 150PL, so when I got the 130P-DS I got a 2" one which was a bit more costly, but not ridiculous. The difference is not just on lights with the moon out and as well as making the LP gradient easier to process out (it doesn't disappear) it helps bring out fainter objects.

I don't do a lot of visual but I'm hoping to do a bit more, and my experience is it seems to help contrast quite a bit, but I tend to go for easy objects...

It was also a bit of a surprise to realise I didn't need it when I went to a proper dark sky site!

I've also had a try at narrowband with a baader 7nm ha filter. This obliterates the LP and can virtually remove gradients caused by the moon, but demands long exposures as I use a DSLR.

[PeterCPC]

I have tried all sorts of filters (imaging) such as CLS, UHC etc and have found that IDAS filters give the best results for me using a DSLR. Post processing is easier.

Peter