New CMOS optimised Baader Ultra-Narrowband filters

[rsarwar]

Just realized I have a spectrometer and a monochromator at work using which I could carry out the measurements needed to work out the transmission curves. I only have the ha 3.5nm f3 to f10. So I will try that when I get a chance get the spectrometer working again. 

Edited November 10, 2021 by rsarwar

[Magnum]

On 03/11/2021 at 15:29, tooth_dr said:

I got my new ultra narrowband filters for slower scopes, hoping to have more success with these ones!  This is the third set of filters I've received, and consistent with the previous two sets, the packaging is partly missing in 2 out of the 3 filter boxes.  Does it matter - not really, but the filters arent held securely during storage/shipping, and slightly disappointing QC.  In the photo below, there is no padding above the Oiii or Sii filters.

 

Are you gonna try them on the Epsilon at f2.8 on the squid again, I know you say you've exchange to the slower ones to use on your slower scope but you might find these ones work well on both. Im really interested so see your results as I image at a range of f ratios from 7.5 to 4.5 and also have the sayang f2 lens which I generally use at f2.4 but don't mind stopping down to 2.8 if that stopped them going off band. really can't afford to get 2 sets so planning towards the slower ones as I can alter the speed lens but not the scopes LOL.

I currently use badder 7nm which seems to work down to 2.4, never tried f2 as the lens needs to but stopped down 1 click anyway for best star shapes.

So torn between these or the Antlias

Lee

[Magnum]

P.S does anyone know what Baader mean by CMOS optimised, as I cant for the life of me see how a line filter would perform different on cmos vs ccd, sounds like marketing to me. I could see that LRGB could be optimised as some cmos have greater UV/IR sensitivity and require stronger UV?IR blocking  but that's at either end of spectrum not in the middle.

 

Edited November 12, 2021 by Magnum

[tooth_dr]

5 hours ago, Magnum said:

Are you gonna try them on the Epsilon at f2.8 on the squid again, I know you say you've exchange to the slower ones to use on your slower scope but you might find these ones work well on both. Im really interested so see your results as I image at a range of f ratios from 7.5 to 4.5 and also have the sayang f2 lens which I generally use at f2.4 but don't mind stopping down to 2.8 if that stopped them going off band. really can't afford to get 2 sets so planning towards the slower ones as I can alter the speed lens but not the scopes LOL.

I currently use badder 7nm which seems to work down to 2.4, never tried f2 as the lens needs to but stopped down 1 click anyway for best star shapes.

So torn between these or the Antlias

Lee

Hi Lee

FLO and Baader both said that the slow ones won’t work on the fast scope.  I have since swapped over the mono and OSC cameras.  The QHY camera has a different back focus to the 17.5mm of the ZWO so I can’t even just screw off and swop the cameras easily. So I won’t be able to try out the slower filters on the fast scope.  I too have used ‘normal’ 7nm narrowband filters on the Tak and they worked great so I suspect these would work too.

I agree CMOS optimised is just marketing blurb.  I’ve lost respect for Baader to be honest, too much marketing hype that I bought into.

[Magnum]

1 hour ago, tooth_dr said:

Hi Lee

FLO and Baader both said that the slow ones won’t work on the fast scope.  I have since swapped over the mono and OSC cameras.  The QHY camera has a different back focus to the 17.5mm of the ZWO so I can’t even just screw off and swop the cameras easily. So I won’t be able to try out the slower filters on the fast scope.  I too have used ‘normal’ 7nm narrowband filters on the Tak and they worked great so I suspect these would work too.

I agree CMOS optimised is just marketing blurb.  I’ve lost respect for Baader to be honest, too much marketing hype that I bought into.

I would still try them at 2.8, antlia state that theirs work from f10 down to f3 but there are also loads of images with them using f2 rasas albeit with some vignetting . I think you just might get away with using them at f2.8. Wont hurt to try.

[Magnum]

On 12/11/2021 at 19:08, tooth_dr said:

Hi Lee

FLO and Baader both said that the slow ones won’t work on the fast scope.  I have since swapped over the mono and OSC cameras.  The QHY camera has a different back focus to the 17.5mm of the ZWO so I can’t even just screw off and swop the cameras easily. So I won’t be able to try out the slower filters on the fast scope.  I too have used ‘normal’ 7nm narrowband filters on the Tak and they worked great so I suspect these would work too.

I agree CMOS optimised is just marketing blurb.  I’ve lost respect for Baader to be honest, too much marketing hype that I bought into.

have you managed to get any photons through them yet?

Cheers

[tooth_dr]

7 hours ago, Magnum said:

have you managed to get any photons through them yet?

Cheers

Haven’t got any further than photo below. I bought a new scope so swapping over bits and running new wiring, setting up spacing with the FR, etc. Possibly looking clear Sunday so aiming to get a run then with the new filters, I’ll post images here 👍🏻

 

[david_taurus83]

23 minutes ago, tooth_dr said:

 

Wall-E 2.0?!

[tooth_dr]

15 minutes ago, david_taurus83 said:

Wall-E 2.0?!

David, I was literally just thinking that a few minutes ago!  Didn’t occur to me until I posted the photo above.

On a separate note, I have your OAG installed - perfect.  Unfortunately the 17-23mm variable spacer I bought is 1mm to long at the shortest span. 

[jjosefsen]

22 hours ago, tooth_dr said:

Haven’t got any further than photo below. I bought a new scope so swapping over bits and running new wiring, setting up spacing with the FR, etc. Possibly looking clear Sunday so aiming to get a run then with the new filters, I’ll post images here 👍🏻

 

This thing looks insane

I have to ask.. what do you have on there? APM something.. 

[Louis D]

On 12/11/2021 at 07:34, Magnum said:

P.S does anyone know what Baader mean by CMOS optimised, as I cant for the life of me see how a line filter would perform different on cmos vs ccd, sounds like marketing to me.

I know some camera lenses like the Tamron Adaptall-2 SP 90mm Macro f/2.5 had a violet hot-spotting issue with digital sensors that was nonexistent with film.  It was due to a reflection off the digital sensor back to the near planar rear element and then back to the sensor:

Perhaps Baader has better controlled the reflections from the back of the filter than previously?

[tooth_dr]

I managed to grab a few quick subs last night between the heavy showers and the clouds.  I took a sub of IC1396 and noticed a sizeable enough halo around mu cephei.  

[tooth_dr]

NGC1499 from last night.  It was just a setting up session to test out the dual rig and get the scopes aligned.

The 3.5nm F3.5-F10 Ha fliter coped pretty well being so close to the Moon.  I've also attached the data I took with the NBZ filter, Ha extracted.  Significantly worse but I expected that, and the Oiii from the NBZ filter was non-existent.

I can see a halo in Ha👎

 

 

[tooth_dr]

Here is the Oiii filter - California nebula and M45 (only clear patch of sky)

 

[TakMan]

Jesus, that’s worse than mine (which I sent back) - Baader certainly ‘found a way’, not sure what ‘way’ they were looking for, just not halo reduction! 😳

[GalaxyGael]

On 12/11/2021 at 19:08, tooth_dr said:

I agree CMOS optimised is just marketing blurb.  I’ve lost respect for Baader to be honest, too much marketing hype that I bought into.

I agree, and optimization for CMOS has no useful meaning either. A fast scope is fast irrespective of the sensor type viz. the contribution of the filter, small pixel CMOS or larger pixel CCD. It interests me (overlap with my daily work) that the graded refractive index layers on these filters are thick enough to be sensitive to optical thickness with incident light angle, and yet no texturization of the air-interfacing surface for wavelengths other than those being passed is made to minimize back reflections of rejected light especially for tight bandpass filtration. Minimizing this effect is used all the time in other fields, yet the halos are a bane in photography still.

[tooth_dr]

19 hours ago, TakMan said:

Jesus, that’s worse than mine (which I sent back) - Baader certainly ‘found a way’, not sure what ‘way’ they were looking for, just not halo reduction! 😳

Where do I go from here Damian 😕

Is it my optics?  Just emailed Baader

 

Edited November 25, 2021 by tooth_dr

[tooth_dr]

9 minutes ago, GalaxyGael said:

I agree, and optimization for CMOS has no useful meaning either. A fast scope is fast irrespective of the sensor type viz. the contribution of the filter, small pixel CMOS or larger pixel CCD. It interests me (overlap with my daily work) that the graded refractive index layers on these filters are thick enough to be sensitive to optical thickness with incident light angle, and yet no texturization of the air-interfacing surface for wavelengths other than those being passed is made to minimize back reflections of rejected light especially for tight bandpass filtration. Minimizing this effect is used all the time in other fields, yet the halos are a bane in photography still.

Are the haloes caused by other unwanted wavelengths not sufficiently suppressed?  Is this the difference with the likes of Chroma or Astrodon?

[GalaxyGael]

I would like to get a hold of a few filters that no-one wants and get cross-sections sliced under our focused ion beam milling system and analyzed in very high resolution electron microscopy. Composition, layering, thickness etc. are all easily extracted and even visualized. Short answer is I don't know, without knowing what differences there are in the filter coating procedures, thickness, refractive indices, number of layers and whether it uses angle-dependent reflectivity or interference rejection, or actual absorbance-based filtering. The former has a much higher chance of halos since those photons are formally reflected somewhere and back-reflected from interference between the two surfaces of the filter (since they are 'coated' on either side by air).

Path lengths in the optical train is a real consideration, but more so in the filter itself. Where the filter is in relation to the sensor. In some cases, the situation is worse when it is in a filter drawer attached next to the camera and for the APO, it can be better to have it scope side of the flattener for backfocus considerations but also from reflectivity concerns. Photons of different wavelength see a different optical thickness and angle changes in fast systems can affect transmission, but I am curious why astrodons and also chromas too are better. Often, in other areas, the outer surface is texturized with roughness features that scatter unwanted wavelengths and pass the ones you want to prevent the constructive interference problem, but I have no idea of this is used in optical filters such as these- I doubt it. Roughness or porosity brings down the refractive index of the very outer surface of a filter to match the air next to it, minimizing reflection. The more common way is to use multilayers that make a graded drop in refractive index to get a similar effect (magnesium fluoride is a good example, among many others). If you match refractive indices, you have zero reflections. Good example is a glass beaker filled with oil of the same refractive index. when another glass beaker is dropped into the oil, it disappears since the whole thing has no index contrast and so no reflectivity.

If the filter is designed to pass only 656 nm +/- 1.5nm for a 3 nm Ha filter let's say, then that is the photon energy that hits the UV-IR cut (or whatever you have, AR glass e.g.) inbuilt on the camera, and then the cover slip and then the sensor. The halo comes from reflection back to the sensor from interference within the filter and optical elements, but in these filters that is a function of the interference filtration by a number of successively coated layers on the glass - they didnt optimize this I think. I took a graph from one of our studies some years ago showing visible spectrum reflectance through a multilayer antireflection coating. It is a dispersive material, designed to be that way for a different reason so that energy (reflectance) drops for longer wavelengths (ED glass and fluorite avoid this, among other benefits). Anyway, the oscillation is caused by the nature of the multilayered structure, enhanced or suppressed interference. You can pick which light wavelength is reflected more and it depends also on the angle of the incident light (not shown in this plot).

 

All filters get all the spectrum initially and at all angles that allow light to hit the filter, but only pass some of it, suppressing others by interference I'm guessing. But if the coatings are not sufficiently dispersive in the rejected photon energy range, they could get reflected and detected especially at different angles. What I do not know without being able to analyse one of these filters, is whether they have maximum transmission for the light you want and minimum transmission for all the rest at a particular angle. Our example is standard 45 degree reflectance and all the peaks and troughs shift if the angle changes. The second plot I show is another nanomaterial coating that is designed to match the air refractive index and kill reflectivity, and it shifts with angle.

A couple of these filters in our angle-resolved transmission setup could show definitively what the transmission characteristics are with angle and how they compare under identical illumination - a nice 4th year project come to think of it. Filter makers never state (do they, anyone know?) at what angle or what conditions the transmission spectra for their filter are, whether it is straight through, collimated transmission only etc. Have you tried putting the filter in backwards (if it is one where the direction is indicated) to see if there is a change? Maybe astrodons and others with minimum halo artefacts have designed the layers so that interference and back-reflections are minimized, but all filters can be chopped up and examined down to atomic resolution. We can see exactly what they put on them, what its made from, how thick, how many layers, and why the behave the way they do.  right now, there seems to be no literature for making a definitive link between the issues and the nature of the filters (good ones and bad ones) to see how much of an influence it has. 

and there are batch to batch problems with some of them too, the astro-product lottery is too often reported.

 

[TakMan]

On 24/11/2021 at 21:45, tooth_dr said:

Where do I go from here Damian 😕

Is it my optics?  Just emailed Baader

 

If you were going with the Epsilon, then I'd have said take a look on CN 'Experienced Imaging' and take a look at the 'Who's using Astronomic High Speed Filters..?', or something to that effect. They look pretty good for the money. Only 'issue' would be if mixing with other brand LRGB filters as they are only 1mm thick, so could be an issue for focusing... or using an OAG.

I went with 50mm unmounted Chroma's** (in case I ever want to go to full frame). Will save for the LRGB - if I deem that my location justifies the expense of broadband imaging (or just enjoy narrowband) and then go to the Lunar/Solar kit once we move into Galaxy Season. 

**Can't say I've had the opportunity to test yet what with the weather!!!

Edited November 26, 2021 by TakMan

[tooth_dr]

30 minutes ago, TakMan said:

If you were going with the Epsilon, then I'd have said take a look on CN 'Experienced Imaging' and take a look at the 'Who's using Astronomic High Speed Filters..?', or something to that effect. They look pretty good for the money. Only 'issue' would be t=if mixing with other brand LRGB filters as they are only 1mm thick, so could be an issue for focusing... or using an OAG.

I went with 50mm unmounted Chroma's** (in case I ever want to go to full frame). Will save for the LRGB - if I deem that my location justifies the expense of broadband imaging (or just enjoy narrowband) and then go to the Lunar/Solar kit once we move into Galaxy Season. 

**Can't say I've had the opportunity to test yet what with the weather!!!

Baader are looking into it now Damian, just waiting to hear back. I’ve switched to two APMs and parked the Epsilon for the time being, so these are just your normal speed ultra narrow filters.   I just bought a chroma 3nm Oiii on the recommendation of another APM user who is halo-free 

[tooth_dr]

Here we have my comparison photos of the Baader versus Chroma.  I was able to get a 36mm Chroma Oiii filter and I designed and 3d printed myself a holder to use this size of glass in my 2" filter wheel carousel.   I originally printed in white, but ordered some black and reprinted it.  I designed it to fit inside an spare UVIR filter holder.  The original screw-on retaining ring was used to secure the filter.  (Apologies for the slight sidetrack to the thread but 2" chromas were not feasible cost wise)

I took these images below half an hour ago under poor conditions.  120s subs taken one after another with autofocus run before each image.

1) Baader Oiii 4nm

2) Chroma Oiii 3nm

 

 

 

[Louis D]

Sometimes, the cost of a premium upgrade is truly worthwhile.

[Starflyer]

The images say it all, those aren't particularly bright stars but the halos are worse than I get with my old style Baader OIII filter.

[carastro]

An ex member of SGL has sent his Sii Baader Ultranarrowband filter back for testing as he was unable to get any Sii data through it.  Just waiting for a response from Baader.

Carole