97 replies to this topic

[sky-man]

I came across the newest TeleVue UHC Type2 and TeleVue Oiii Type2 filters.  I sent it to an astronomer friend who has a professional laboratory spectroscope.  Let's look at the exact graphs of these filters if he manages to do the test.

I think a real test on a spectroscope of filters in 2023 will remove all the guesswork about them. Also on test will be Lumicon UHC. Are we placing bets?

Attached Thumbnails

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Edited by sky-man, 11 January 2024 - 12:36 PM.

[Starman1]

You can find other lab tests of both on this website:

(My own personal filters are part of the results on the site.)

I invite you to compare your filters with the 101 filter results posted there:

https://searchlight....9d-153d7e7c0eb8

 

TeleVue BandMate II filters are made by Astronomik, so it is illuminating to superimpose the Astronomik graphs on the TeleVues to see the difference.

The Astronomik UHC and Tele Vue Nebustar difference in the red wavelengths is interesting.

 

Unfortunately, some of the filters tested are older ones, and the graphs don't represent current production.

That's a problem with all the other filter test websites, too.

[sky-man]

You always want to have measurements in an alternative laboratory of filters in 2023, and not in 2018, for example, 5 years ago.
Time does not stand still, production can change, even the top Lumicon filters have changed beyond recognition in 5 years and there is no stability. And it was impossible to rely on measurements of filters made 5 years ago, even with Lumicon.
The measurements from your link are distrustful, at least about 99% for TeleVue Oiii, when 94.7% is indicated on the box. I don’t trust the laboratory from your link Don. Either I should not trust what is indicated on the box and trust the tests on your link. There are differences, and strong ones. No offense.

Edited by sky-man, 12 January 2024 - 09:32 AM.

[Starman1]

You always want to have measurements in an alternative laboratory of filters in 2023, and not in 2018, for example, 5 years ago.
Time does not stand still, production can change, even the top Lumicon filters have changed beyond recognition in 5 years and there is no stability. And it was impossible to rely on measurements of filters made 5 years ago, even with Lumicon.
The measurements from your link are distrustful, at least about 99% for TeleVue Oiii, when 94.7% is indicated on the box. I don’t trust the laboratory from your link Don. Either I should not trust what is indicated on the box and trust the tests on your link. There are differences, and strong ones. No offense.

I find that peak transmission varies, from having 10 samples at a time in inventory, from 93%+/- to close to 99%+/-

That is the nature of filters--there is at least a +/- 2-3nm difference in bandwidth and bandwidth placement among a batch of filters, and up to a 6% difference in peak transmission.

The cheaper the filter, the larger that variation seemed to be among the filters I sold for many years.

There is no batch of filters where the transmission peak is identical from filter to filter.

 

I agree that seeing tests for current batches is desirable, but simply not possible when the manufacturers are not testing each individual filter and giving you test data with each one

(the most recent Lumicon filters, for example, tested one filter in a batch, then provided that same graph with every filter in the batch).

You would have to buy filters and have them tested at the same time, which is what I did with ~50 filters.

 

The TeleVue BMII O-III box for the high transmission filter said peak transmission 98.7%, by the way, and I regard a measurement of +/- 2% to be within tolerances for measurement accuracy.

 

I note that, as is typical for filters, the higher the transmission, the wider the bandwidth.

And if you look closely at the TeleVue BMII O-III tests on the Semrock site, you'll see that holds true with the TeleVue BMII O-III filters as well.

Since the Astronomik filters tested were current ones (from batches after they changed specs, and identical to the TeleVue BandMate II O-III), you can superimpose those curves on the TeleVue BMII O-III filters as well.

It will give you some examples of how the bandwidths and bandwidth placements vary from filter to filter.

 

The curves on the site are generated by an independent lab, having no affiliation with any manufacturer and represent actual lab measurements with the same instrument.

 

The latest specs of filters occurred in:

2016-17 for Astronomik

2018 for TeleVue

2018 for Lumicon

 

The specs have not changed since then, though individual filters will vary, sometimes distressingly so.

It's always desirable to test an individual filter to see what you get.

Look at the Lumicon UHC filter 2018 (a Gen.3 filter) on the Semrock site to see how high transmission can get.

That filter measured 99.8% at 486nm, 99.5% at 496nm, and 99.3% at 501nm.

It was about 7% higher transmission than a 2010 Lumicon UHC filter, but the bandwidth was quite a bit wider on the 2018 filter (FWHM bandwidths 27nm vs.22nm).

Despite the lower transmission, the narrower bandwidth filter yields better contrast and outperforms the newer one.

[sky-man]

Look at the Lumicon UHC filter 2018 (a Gen.3 filter) on the Semrock site to see how high transmission can get.
That filter measured 99.8% at 486nm, 99.5% at 496nm, and 99.3% at 501nm.
It was about 7% higher transmission than a 2010 Lumicon UHC filter, but the bandwidth was quite a bit wider on the 2018 filter (FWHM bandwidths 27nm vs.22nm).
Despite the lower transmission, the narrower bandwidth filter yields better contrast and outperforms the newer one.

Thanks Don for your detailed response. You definitely know what you're talking about. I agree with you, that’s why I want to test my filters.
The test will be ready in the middle of next week.

Edited by sky-man, 13 January 2024 - 07:09 AM.

[sky-man]

Thanks to Dmitry Makolkin for the laboratory test on a professional russian spectrophotometer SF-56.

 

Lumicon UHC 2005-2012 showed:
Oiii 500nm - 96.8%
Oiii 496nm - 96.8%
Hb 486 nm - 94%
Width at 50% - 24nm

 

TeleVue UHC 2023 showed:
Oiii 500nm - 95.5%
Oiii 496nm - 97.5%
Hb 486 nm - 94%
Width at 50% - 27nm

 

Lumicon UHC 1.25", great period between 2005 and 2012:

 

Televue Bandmate Type 2 Nebustar 1.25" 2023:

 

What we see is that the Lumicon UHС filter, produced almost 20 years ago, is no worse in transmission than the newest TeleVue UHC. The transmittance is similar, but the width of Lumcon UHC is narrower by 3 nm.

 

It should be noted that TeleVue does not have a violet spectrum like Lumcon UHC. This may slightly degrade sharpness on achromats, showing spherical aberration and larger star size. As for red, both filters have no visible red spectrum.

Edited by sky-man, 19 January 2024 - 06:32 PM.

[sky-man]

Thanks to Dmitry Makolkin for the laboratory test on a professional russian spectrophotometer SF-56.

 

TeleVue Oiii 2023 showed:
Oiii 500nm - 94%
Oiii 496nm - 93%
Width at 50% - 12.5 nm

 

Tevevue Bandmate Type 2 OIII  1.25" 2023:

 

What do we see here with the newest filter Oiii TeleVue 2023. There are no 99%, this is a regular Astronomik Oiii filter with a transmittance of 94%. Width 12.5 nm. This is a very good visual filter with high contrast.

 

Filters on the test:

 

 

Edited by sky-man, 19 January 2024 - 06:26 PM.

[Starman1]

Thanks to Dmitry Makolkin for the laboratory test on a professional russian spectrophotometer SF-56.

 

Lumicon UHC 2005-2012 showed:
Oiii 500nm - 96.8%
Oiii 496nm - 96.8%
Hb 486 nm - 94%
Width at 50% - 24nm

 

TeleVue UHC 2023 showed:
Oiii 500nm - 95.5%
Oiii 496nm - 97.5%
Hb 486 nm - 94%
Width at 50% - 27nm

 

Lumicon UHC 1.25", great period between 2005 and 2012:

Lumicon_UHC.PNG

 

Televue Bandmate Type 2 Nebustar 1.25" 2023:

Televue_Bandmate_Type2_Nebustar.PNG

 

What we see is that the Lumicon UHС filter, produced almost 20 years ago, is no worse in transmission than the newest TeleVue UHC. The transmittance is similar, but the width of Lumcon UHC is narrower by 3 nm.

 

It should be noted that TeleVue does not have a violet spectrum like Lumcon UHC. This may slightly degrade sharpness on achromats, showing spherical aberration and larger star size. As for red, both filters have no visible red spectrum.

This is my finding as well.  The earlier filter had a narrower bandwidth............band..H-ß....495.9..500.7..656.3....FWHM

My Lumicon UHC filter from 2010 had measured specs of                                22    93.4    93.3    92.1    N/A      482 504

My 2018 TeleVue Nebustar (Astronomik manufacture had measured specs of    26    89.7    96.3    96.1    N/A      481 507

My 2018 Lumicon UHC had measured specs of                                                27    99.8    99.5    99.3    N/A      480 507

Edited by Starman1, 19 January 2024 - 07:05 PM.

[Starman1]

Thanks to Dmitry Makolkin for the laboratory test on a professional russian spectrophotometer SF-56.

 

TeleVue Oiii 2023 showed:
Oiii 500nm - 94%
Oiii 496nm - 93%
Width at 50% - 12.5 nm

 

Tevevue Bandmate Type 2 OIII  1.25" 2023:

Tevevue_Bandmate_Type2_OIII.PNG

 

What do we see here with the newest filter Oiii TeleVue 2023. There are no 99%, this is a regular Astronomik Oiii filter with a transmittance of 94%. Width 12.5 nm. This is a very good visual filter with high contrast.

 

Filters on the test:

IMG_3444.JPG

 

 

post-338930-0-18294900-1700085093.jpg

Consistent with what I found, too, though my Tele Vue was a "ringer".

The measured responses of:

measured parameter............band..H-ß...495.9...500.7...656.3....FWHM

TeleVue O-III 2018               12     1.6     99.2     98.4     N/A      492 504
New Lumicon O-III 2018       11     3.5     95.1     94.7     N/A      494 505

 

I sold TeleVue and Astronomik for years, and the range of peak transmission ranged from a low of 92% to a high of 99%, showing the variation from batch to batch and from filter to filter.

Edited by Starman1, 19 January 2024 - 07:12 PM.

[f18dad]

Consistent with what I found, too, though my Tele Vue was a "ringer".

The measured responses of:

measured parameter............band..H-ß...495.9...500.7...656.3....FWHM

TeleVue O-III 2018               12     1.6     99.2     98.4     N/A      492 504
New Lumicon O-III 2018       11     3.5     95.1     94.7     N/A      494 505

 

I sold TeleVue and Astronomik for years, and the range of peak transmission ranged from a low of 92% to a high of 99%, showing the variation from batch to batch and from filter to filter.

Hi Don, I have the Bandmate II Nebustar and OIII purchased new in Feb 2021. TV states the following:

 

"Each filter is: optically tested by Tele Vue in high power-space to ensure no image degradation, tested by Astronomik on a spectrograph to ensure the coating meets design specifications"

 

I do not know how to interpret the information on my cases. Can you explain? 1.) Is each filter tested and the "T max:" is the result of the transmission for that particular sample?, or 2.) This is a batch report or even a general average?

 

Since TV says that "Each filter is optically tested" and "tested by Astronomik on a spectrograph" are the results of these tests kept on file and available since each filter has a corresponding S/N?

 

I was considering calling TV about this but thought I would ask here first. Below is the case information on each of my Bandmate II's. Any interpretation or comment?

 

 

 

Edited by f18dad, 15 February 2024 - 06:10 AM.

[sixela]

Another data point: Astronomik UHC, tested yesterday on an Ocean Optics spectrometer (calibrated using neon lamp rays and validated on a solar spectrum's absorption lines).

The passbands may be up to 0.2nm narrower than indicated here because of the spectrometer resolution, and the maximum transmission may be underestimated by 1% or so. Blueshift measured for the half-cone angle for the edge of f/4.6 optics in dashed graph.



And yes, it has the not-a-Televue H-alpha to near IR pass characteristics, should you want to use it as a sort-of dual band imaging filter:

Edited by sixela, 15 February 2024 - 04:55 AM.

[Starman1]

Hi Don, I have the Bandmate II Nebustar and OIII purchased new in Feb 2021. TV states the following:

"Each filter is: optically tested by Tele Vue in high power-space to ensure no image degradation, tested by Astronomik on a spectrograph to ensure the coating meets design specifications"

I do not know how to interpret the information on my cases. Can you explain? 1.) Is each filter tested and the "T max:" is the result of the transmission for that particular sample?, or 2.) This is a batch report or even a general average?

Since TV says that "Each filter is optically tested" and "tested by Astronomik on a spectrograph" are the results of these tests kept on file and available since each filter has a corresponding S/N?

I was considering calling TV about this but thought I would ask here first. Below is the case information on each of my Bandmate II's. Any interpretation or comment?

IMG_9769.jpg


IMG_9770.jpg

T.Max is the peak transmission % for that filter, though it doesn't specify at which wavelength. The other figure is the f/ratio range that filter works with. That tells you a bit about the bandwidth placement and the bandwidth itself. A bandwidth placed for a short f/ratio will be more desirable for a short f/ratio scope, while a higher peak transmission can indicate a wider bandwidth or simply a higher quality coating process.
I sold filters from Astronomik for years. Every filter had different numbers.
Both of yours have excellent specs.

Edited by Starman1, 15 February 2024 - 10:39 AM.

[sixela]

"f/infinity to f/XX" means that Astronomik measured it to have the emission lines of interest in the flat top of the transmission curve (i.e. it's not redshifted enough to materially affect the transmission for an infinitely slow telescope).

The wider the bandpass and the more it's redshifted with respect to the emission line (while still not being redshifted far enough to make the filter transmission drop for f/infinity), the lower the max. f/ratio after the "to".

Of course these have quite a moderate blueshift (a high effective index of refraction) and quite some reserve in the FWHM to cope with some blueshift, so that's why the f/XX numbers are so low.

Edited by sixela, 15 February 2024 - 01:52 PM.

[f18dad]

T.Max is the peak transmission % for that filter, though it doesn't specify at which wavelength. The other figure is the f/ratio range that filter works with. That tells you a bit about the bandwidth placement and the bandwidth itself. A bandwidth placed for a short f/ratio will be more desirable for a short f/ratio scope, while a higher peak transmission can indicate a wider bandwidth or simply a higher quality coating process.
I sold filters from Astronomik for years. Every filter had different numbers.
Both of yours have excellent specs.

 

Thank you!

[sixela]

And, for the record, we just measured Tmax independently on different types of Astronomik filters and the numbers are what they should be based on the label. The label also refers to a S/N etched on the edge of the filter.

So it looks like Astronomik do test these filters individually with a high resolution spectrometer.

[f18dad]

And, for the record, we just measured Tmax independently on different types of Astronomik filters and the numbers are what they should be based on the label. The label also refers to a S/N etched on the edge of the filter.

So it looks like Astronomik do test these filters individually with a high resolution spectrometer.

 

That's just awesome to know. Thanks for doing that!

[sixela]

To give you an idea of how wild the passband variations can be on narrow Chinese filters, here is the H-alpha passband of three Optolong L-Ultimates:



The filter with an orange line had a quite nice passband shape (for OIII too) with fairly good transmission, but alas is really badly blueshifted, making it unattractive on scopes slower than f/4.7. It's the best filter above that f/ratio, though.

The filter with a blue line is my current filter, and is what you'd expect for a filter from f/infinity to f/4 (and slightly below). Shame that the transmission also suffers a bit though.

The filter with a green line is even more preshifted and would be the filter of choice on an f/3. Transmission is the worst of the lot above f/5 though (although it remains usable).

The mean seems to be for a passband slightly redshifted (as it should be) but the spread is really colossal. Oh, and these are not "3nm" filters but 4nm filters.

The slower your scope the less likely you are to be really unlucky with these (you'll be using the graph just right of the red H-alpha peak for slow scopes).

Edited by sixela, 16 February 2024 - 07:02 PM.

[Tubuskahusk]

I just wanted to give people a heads up. DGM now has first run NPB filters in stock. Dan said he is having issues updating the site so that is why they show out of stock still. I contacted him a little over a month ago and he told me about when they would be back in stock. He then contacted me when they came in.I have been waiting for a month on them to get some back in stock and ordered one this morning. I only posted this because some people were waiting to order one. I get nothing out of posting this.

Edited by Tubuskahusk, 20 February 2024 - 07:24 PM.

[Robocop87]

Hi everyone. What I'm wondering is whether it makes sense to buy an uhc filter given that today all the lights in cities and towns are LED. I'm confused and don't know whether to get a filter.

[Starman1]

Hi everyone. What I'm wondering is whether it makes sense to buy an uhc filter given that today all the lights in cities and towns are LED. I'm confused and don't know whether to get a filter.

A good UHC type filter will pass only about 7% of the visible spectrum.

Even with LEDs, most of the light from lights will be outside the bandwidth of the filter.  A nebula filter will make a huge difference.

It does here in LA, the home of light pollution.

 

Just be sure its bandwidth is in the 22-27nm range.  Wider filters are significantly less effective,

[Robocop87]

I observe from the mountains of central Italy with an excellent sky. Thank you

[Robocop87]

A good UHC type filter will pass only about 7% of the visible spectrum.
Even with LEDs, most of the light from lights will be outside the bandwidth of the filter. A nebula filter will make a huge difference.
It does here in LA, the home of light pollution.

Just be sure its bandwidth is in the 22-27nm range. Wider filters are significantly less effective,

I forgot....I'll take the astronomik UHC filter

[Starman1]

I forgot....I'll take the astronomik UHC filter

Excellent choice.