97 replies to this topic

[ASTROMILK]

The Baader UHC-S is a very good broadband filter. It's been around for many years. My sample has a 62nm bandwidth in the blue-green and an unlimited bandwidth in the red.
I preferred it to the Lumicon Deep Sky and the Orion Sky Glow.
As such, it will enhance contrast only a tiny bit, and really won't come into its own until the skies are quite dark (say, 21.2mpsas or darker), more like Bortle 3-4.
There, a small increase in contrast might be noticeable.

Even there, the UHC-S only has a small effect, and contrast is only slightly enhanced.
Where I find the filter handy is on objects like M20, where narrowband filters simply kill the reflection nebulosity and enhance the emission part.
The UHC-S doesn't kill the reflection part, but enhances the emission part significantly less.

In a city, they often render the effects of light pollution WORSE, by creating a lot of light scatter internally in the filter.

There are some valid reasons to have a good broadband filter, but it would be AFTER you have a good narrowband, O-III, and H-ß filter.
Any UHC filter labeled UHC-S, UHC-E, UHC/LPR or UHC/CLS is not really a narrowband filter.
From the standpoint of contrast enhancement, they should just be called "contrast filters", and leave off "ultra high".

A true "nebula filter", like the ones I mentioned in the quoted post, IS useful in a city. But the broadband? Not so much.

Alright looks like I’ll have to save up. I know some accessories are okay to cheap out on or buy other than premium, still learning which ones I need to invest in.


Thanks again Don! I’ve learned so much from your replies!

-Milk

[vancedailey]

Hi Don,

Do you have any experience with the Optolong UHC and the Optolong O-III?

They are reasonably priced and yet I know Optolong makes some high quality filters for photography.

I am a visual observer in a suburban area.

Thanks,

Vance

[Starman1]

Yes, as these were filters I tested.

Both are exceedingly wide for their types.

Unless they are very cheap, I would avoid them for visual use.

The UHC had a 48nm bandwidth, almost twice as wide as preferred.

The O-III had an 18nm bandwidth, about 1.5x as wide as preferred.

Orion filters are also reasonably priced and have better bandwidths.

[MikiBee]

Don, thanks for this compilation,  it's a lot of hard work.

 

If you were to pick two filters to be used with apertures 4, 5, 8 inches, in urban, light polluted skies for astronomy outreach to impress beginner astronomers and astronomers-to-be on a variety of deep sky objects, what would those two be?

 

Thx

[Starman1]

1) a narrowband, UHC-type, filter.

TeleVue BandMate II Nebustar, Lumicon UHC Gen.3, Astronomik UHC visual, DGM NPB, Orion UtraBlock.

2) O-III filter

TeleVue Band Mate II O-III, Lumicon O-III Gen.3, Astronomik O-III visual (12nm)

David Knisely's summary of best filter type for each nebula (remember, a narrowband also passes the H-ß spectral line):

Attached Files

•  BestNebulaFilter-Knisely Summary.xls   31KB   233 downloads

Edited by Starman1, 05 December 2022 - 09:45 AM.

[MikiBee]

Thx a bunch, this is kind of what I had in mind and also in my modest collection (+ an H-Beta), all entry level though, maybe worth upgrading one day.

 

Clear nights.,.

[Duncan_R]

Hi guys! Just joined the forum)
I was wondering if the Optolong L-Enhance filter can be used as a narrowband UHC filter for visual observing?
It appeared to have just right bandwidth.
Did anybody compare it to Lumicon UHC, Astronomik UHC or Orion Ultrablock filters?

Edited by Duncan_R, 12 December 2022 - 06:08 AM.

[Starman1]

I've seen the spectrum, and it looks like it might work quite well as a visual filter.

Since it's oriented to photography, there won't be many visual observers who have used it.

If you do both imaging and visual use, it might be a good one to try out.

 

Antlia, another imaging filter company, has a "H-ß + O-III" narrowband filter as well, but only in 1.25".

 

It's important to remember that nebula filters are used at low powers.

If your low powers are 1.25", that filter size is fine.

But a large number of visual astronomers use 2" eyepieces at low power.

Edited by Starman1, 12 December 2022 - 10:58 AM.

[Duncan_R]

Thank you for your help

[PYeomans]

Returning old timer here, what significant differences are there between the Lumicon UHC and Baader 8nm OIII I bought  15 years ago  and current Gen 3 models?      

[Starman1]

Returning old timer here, what significant differences are there between the Lumicon UHC and Baader 8nm OIII I bought  15 years ago  and current Gen 3 models?      

The Lumicon UHC has had many generations, actually:

1979-2001 1st owner original sandwich construction.  All are failing now.

2001-2005 2nd owner better filter, single substrate, but fragile Pre-IAD coatings

2005-2012 modern IAD coatings, incredible performance.  bandwidths from 21-24nm.

2012-2016 3rd owner, 3rd mfr.  some problems in QC, but good when no QC problem.

2016-2018 4th owner. cheap import filters, recently sold as "Economy UHC filters"

2018-now called "Gen.3" high end filter made with IAD and the equal of the 2005-2012 ones.  Slightly wider bandwidth to accommodate f/2-f/4 scopes.

Current UHCs are a 26-27nm bandwidth and this bandwidth accommodates new shortest f/ratio scopes.

Other similar filters: TeleVue Bandmate II Nebustar, Astronomik UHC, DGM NPB.

 

The Baader 8nm O-III filter only picks up the 500.7nm O-III line and identifies it as a photographic filter.

A visual use O-III filter will have at least an 11-12nm bandwidth and also transmit the 495.9nm spectral line.

The new Gen.3 O-III filter is a high end IAD filter with an 11-12nm bandwidth which passes both O-III lines with a high %.

Other similar filters: TeleVue BandMate II O-III, Astronomik O-III visual.

Edited by Starman1, 16 December 2022 - 03:37 PM.

[PYeomans]

The Baader filter identifies as a visual filter on the pkg and filter. Not so?  Any way to tell which gen UHC the Lumicon is? No markings on filter itself.  

[Starman1]

The Baader filter identifies as a visual filter on the pkg and filter. Not so?  Any way to tell which gen UHC the Lumicon is? No markings on filter itself.  

Yes, it can be used visually, but it is darker and displays less nebulosity than a purely-visual O-III filter.

At best, you could charitably call it a photo-visual filter.

Very experienced observers with filters might have several O-III filters of various bandwidths to display different internal details in a nebula,

but most people have just one O-III filter, and that filter should pass BOTH O-III lines to see the maximum nebulosity.

Additionally, the Baader O-III peaks at a fairly low transmission %.  Mine peaked at 89%, and that was a higher % than most tested.

 

There is a way to identify the approximate date of the Lumicon UHC filter.  Send me a picture of the filter and the box in a private message and I'll try to narrow it down.

If the filter has no markings on the filter housing, however, it is pre-2012.  Just when might be determinable from the box.

Edited by Starman1, 16 December 2022 - 03:46 PM.

[eg71117]

I am a visual observer and was looking at purchasing Lumicon OIII 3rd generation filter.

 

I noticed there are two being offered and both are noted as Generation 3.  The one with the narrowest band 494-505 sells for about $150.  The other notes a band width of 480-507 and sells for $130. Is the extra cost worth it?

 

[Starman1]

Current US retails for Lumicon Gen.3 O-III filters are:

$151.99 for 1.25"

$302.99 for 2.0"

Since they are used at low power, whether you get a 1.25" or 2" will depend on the size of your low power eyepiece(s).

I have one and its lab-tested bandwidth is 494-505nm, actually FWHM of 11.5nm.  It passes both the 495.9nm and 500.7nm O-III lines in the spectrum.

It is an example of a high quality "line" filter.

 

The Lumicon Gen.3 UHC filter also passes the H-ß spectral line, so has a wider bandwidth.

It is a typical high quality "narrowband" filter.

My sample measured a FWHM bandwidth of 480nm-507nm, actually a 27nm bandwidth.

This filter is a more "universal" emission nebula filter, since it passes all the visible energy you are likely to see in a nebula with dark-adapted vision.

Current US prices are:

$129.99 in 1.25"

$302.99 in 2"

 

They are two different filters.  The O-III filter has a narrower bandwidth, yielding higher contrast for O-III features.

But, it is not the best filter if the nebula has strong H-ß emission.

If you'd like a generalization, use a UHC narrowband filter for the large hydrogen gas clouds where stars are forming (M42/M43/M8/M20/M17/M16, etc.)

and use an O-III filter for planetary nebulae/Wolf-Rayet excitation nebulae/supernova remnants.

 

If you get just one, it should be a UHC narrowband filter first.

The Lumicon UHC is currently not in production (but should be fairly soon), and neither is the DGM NPB, a similar filter (but should be fairly soon).

The Astronomik UHC and TeleVue BandMate II Nebustar are similar in quality and are in production and available now.

 

These filters are usually used at magnifications of 10x/inch of aperture and lower.  So if your lowest power eyepiece is a 2", get a 2" filter.

If your lowest power eyepiece is 1.25", then you can get a 1.25" filter.

 

If your refractor has a 2" star diagonal, get a 2" and attach it to the front end of the star diagonal to use it on both sizes of eyepiece.

If your reflector has a 2" focuser, get a 2" and thread it to the bottom of the 2" to 1.25" adapter for use with 1.25" eyepieces.

Edited by Starman1, 17 December 2022 - 12:48 PM.

[Deep Sky Observer]

What do you guys think of the Astro-Tech UHC 1.25" narrowband filters?

[Starman1]

Astrotech advertises the filter as having a 32nm bandwidth.

I have not used one, nor have I seen a test of one, but if the 32nm spec is correct, it could be quite a good value.

It will be used at the lowest powers (under 10x/inch of aperture, or 2.5mm exit pupil and larger), so a 1.25" filter is only appropriate

if your lowest power eyepiece(s) is 1.25".  If it is, this might be a good value.  For the price, that bandwidth, though getting a little wide,

would be far better than most of the inexpensive filters with a 45-50nm bandwidth.

But, for only $22 more, the Orion Ultrablock would be a better filter for contrast.

[six6]

Have you guys heard about the new "SVBONY SV220 Dual-Band 7nm Nebula Filter", found on Aliexpress here.

 

It has a chart like this, looks very different from other narrow-band nebula filter discussed here, so this is different from the like of Orion Ultrablock etc? But they call it Nebula filter... Thanks!

 

 

And a spec sheet from here

 

 

 

Attached Thumbnails

• 
• 

Edited by six6, 02 February 2023 - 03:20 AM.

[Starman1]

The chart shows that it is intended to be a photographic filter, passing the 500.7nm O-III line and the 656nm H-α line (not important for visual).

The graph shows that transmission at 500.7nm is low as well, further pointing to a photographic use, where a longer exposure can make up for low transmission.

The graph does not show the specs listed on the right.

 

This is not a visual filter:

--a visual O-III filter should pass both the 495.9nm and 500.7nm O-III lines.

--the transmission is too low at 500.7nm, making the image darker for visual use

--the H-α line is unimportant for visual use--too deep in the red to have any visual impact at night.

 

In comparison to the Orion Ultrablock, the two filters are as different as apples and oranges.

The Ultrablock passes the 486.1nm H-ß line in the spectrum, as well as the two O-III lines, making it a "universal" visual nebula filter for emission nebulae.

It is a narrowband filter and oriented to visual use.

The Svbony is a photographic-oriented O-III and H-α filter, which makes it useful for photographic imaging of nebulae.

It is a "line" filter, with a narrow bandwidth on each spectral line for maximum photographic contrast.  The graph says it missed the O-III line by a bit, but could still be useful in longer exposures.

[StarAlert]

I wonder how it would work with a NVD.

[Starman1]

I wonder how it would work with a NVD.

For an NVD, you want a broad band transmission in the red that goes well into the infrared.

You want to pick up the H-α, S-II, N-II and so IR to make the nebulae larger and brighter.

Here is an example of a good filter response for an NVD:

Attached Thumbnails

• 

[six6]

The chart shows that it is intended to be a photographic filter, passing the 500.7nm O-III line and the 656nm H-α line (not important for visual).

The graph shows that transmission at 500.7nm is low as well, further pointing to a photographic use, where a longer exposure can make up for low transmission.

The graph does not show the specs listed on the right.

 

This is not a visual filter:

--a visual O-III filter should pass both the 495.9nm and 500.7nm O-III lines.

--the transmission is too low at 500.7nm, making the image darker for visual use

--the H-α line is unimportant for visual use--too deep in the red to have any visual impact at night.

 

In comparison to the Orion Ultrablock, the two filters are as different as apples and oranges.

The Ultrablock passes the 486.1nm H-ß line in the spectrum, as well as the two O-III lines, making it a "universal" visual nebula filter for emission nebulae.

It is a narrowband filter and oriented to visual use.

The Svbony is a photographic-oriented O-III and H-α filter, which makes it useful for photographic imaging of nebulae.

It is a "line" filter, with a narrow bandwidth on each spectral line for maximum photographic contrast.  The graph says it missed the O-III line by a bit, but could still be useful in longer exposures.

Thanks Don! I was wondering if this is worth a try for visual, but no...

[ButterFly]

For an NVD, you want a broad band transmission in the red that goes well into the infrared.

You want to pick up the H-α, S-II, N-II and so IR to make the nebulae larger and brighter.

Here is an example of a good filter response for an NVD:

 

We don't know what happens to the right of that chart, so that chart alone isn't a good place to start.

A narrow h-alpha filter should come first.  6nm is a good place to start.

 

Under dark skies, IR pass filters aren't very helpful (natural skyglow grows in IR due to OH emissions).  For light polluted skies, a 685nm+ IR pass (Baader) is a good start.  It misses h-alpha (656.3), but that's okay - that's what the h-alpha filter is for.  Under darker skies, this filter is good for shutting off the nebula and seeing just the cluster.  A 642+ filter (Astronomik, Lumicon Night Sky H-alpha) lets the h-alpha through, but it gets largely swamped by the IR that also gets through.  I prefer these for general use under my Bortle 5 yard than a 685.

 

Visual filters that let through OIII/h-beta may be useful as IR pass filters.  Their IR characteristics are very hard to track down, simply because they are designed for visual use.  Mike Lockwood's page add a few filters every so often, but most other spectral measurements stop around 700nm.  Astronomik's UHC-E is reported as a good IR pass filter.  I have a Baader UHC-S, which acts like a very broad (35nm) h-alpha filter with a broad (100nm) OIII-h-beta pass.  It leaves very low contrast h-alpha regions but preserves the star cluster.  It is a good HII region cluster filter, even from darker skies, but it's not really an h-alpha filter or an IR pass filter - it's odd but it works where it does.

 

Photographic dual or tri-band filters should be judged for their narrow h-alpha band.  No IR leak is preferable.

 

TLDR:

a narrow h-alpha filter first (~6nm) with no IR leak;

then an IR pass filter (685+ for light polluted skies, 642 for less light polluted skies, can skip for dark skies).

[davidgmd]

TLDR:

a narrow h-alpha filter first (~6nm) with no IR leak;

then an IR pass filter (685+ for light polluted skies, 642 for less light polluted skies, can skip for dark skies).

  
Dumb question for NVD: the above are used separately, not together? Otherwise the H-α lets through only 656 nm, then the IR pass blocks it because it’s shorter than 685?

[ButterFly]

  
Dumb question for NVD: the above are used separately, not together? Otherwise the H-α lets through only 656 nm, then the IR pass blocks it because it’s shorter than 685?

Yes, and they are used for different reasons.

 

Whenever you stack a filter, you multiply the transmission of one with the other to get the total throughput.  As you noticed, anything times zero is zero.  It never makes sense to stack nebula filters.  Colored planetary filters, on the other hand, can be stacked.  They have broader spectra and will leave you with something to work with, rather than zero most places and spikes in a few.