35 replies to this topic

[jimthompson]

Hi Everyone,

 

I am sure some of you have heard about or are already using one of these new narrow tri-band filters.  Perhaps the most popular ones are the OPT Triad and the Optolong L-eNhance.  What you maybe did not know is that these filters are not actually all that new.  They have been around since 2012 but have only really taken off in popularity in the last year or so.  There are presently five commercially available versions of this type of filter:

 

- OPT Radian Triad

- STC Dual Narrowband

- Optolong L-eNhance

- Astro Hutech IDAS-NB1

- Omega Optical Hydrogen & Oxygen Nebula LPF Improved

 

I have procured a sample of all five filters, and am in the midst of testing them.  As usual I will publish a test report when I am done, but in the meantime I thought I'd share some of my preliminary results with everyone.  You can view my test captures to date at the Flickr link below. My next step is to measure each filter's response with my spectrometer.

 

https://flic.kr/s/aHsmHLdaJ4

 

Cheers,

 

Jim T.

[Lorenz0x7BC]

Great news, Jim! Looking forward to your test results!

[pyrasanth]

I've just ordered the Optolong L-eNhance. I will be testing with the QHY168C on my 11" RASA in the next few days (after the filter arrives). It will be interesting to see how well the filter works with fast optics. This filter is mostly promoted as a dual band for HA and OIII but falls into the tri-band because it lets through a bit of Hydrogen B- the only good B source I know of is the Horse Head Nebula so that might be a good test target for this filter.

Edited by pyrasanth, 17 October 2019 - 02:27 PM.

[pyrasanth]

Hi Everyone,

 

I am sure some of you have heard about or are already using one of these new narrow tri-band filters.  Perhaps the most popular ones are the OPT Triad and the Optolong L-eNhance.  What you maybe did not know is that these filters are not actually all that new.  They have been around since 2012 but have only really taken off in popularity in the last year or so.  There are presently five commercially available versions of this type of filter:

 

- OPT Radian Triad

- STC Dual Narrowband

- Optolong L-eNhance

- Astro Hutech IDAS-NB1

- Omega Optical Hydrogen & Oxygen Nebula LPF Improved

 

I have procured a sample of all five filters, and am in the midst of testing them.  As usual I will publish a test report when I am done, but in the meantime I thought I'd share some of my preliminary results with everyone.  You can view my test captures to date at the Flickr link below. My next step is to measure each filter's response with my spectrometer.

 

https://flic.kr/s/aHsmHLdaJ4

 

Cheers,

 

Jim T.

Hi Jim,

 

I looked at the initial integrations you posted on Flicker and it certainly gives a good insight to how these filters are going to potentially perform.

 

I think this is a study that you need to invest time in to give meaningful comparisons. I would hope you can run rudimentary calibration. It would be good to see this as the data becomes meaningful if this is done. The images you have presented are understandably noisy with varying degrees of gradient and it can be hard to tell what is attributable to the filter or the local sky conditions. However- it is easy to be critical so I shall look forward to your results in the future against the structured testing which I'm sure you are planning- please don't rush the results out- it is really important to be objective.

[jimthompson]

Hi Jim,

 

I looked at the initial integrations you posted on Flicker and it certainly gives a good insight to how these filters are going to potentially perform.

 

I think this is a study that you need to invest time in to give meaningful comparisons. I would hope you can run rudimentary calibration. It would be good to see this as the data becomes meaningful if this is done. The images you have presented are understandably noisy with varying degrees of gradient and it can be hard to tell what is attributable to the filter or the local sky conditions. However- it is easy to be critical so I shall look forward to your results in the future against the structured testing which I'm sure you are planning- please don't rush the results out- it is really important to be objective.

Hi pyrasanth,

 

I do not intend to perform any sort of frame calibration other than dark frames.  Although these filters have applications in astrophotography, that is not my area of interest.  My application is for video observing, thus explaining the relatively short exposures of my collected images.  I intend to rely more on analysis to compare the relative performance of these filters, with the test images highlighting more subjective characteristics like colour balance.  At the end of the day I believe the outcome of my testing will be that these filters all perform pretty similarly, which then raises the question:  why would anyone pay $1k for the 2" OPT version?

 

Best Regards,

 

Jim T.

[pyrasanth]

Hi Jim,

 

Thanks for the additional information.

 

If you establish any subtlety between the mid range & top end then you have your reason for the very high price differential. It will probably boil down to the Badder-Chroma-Astrodon debate which has raged since I've been imaging- the law of ever diminishing returns. However I would not pay $1K for one filter unless I clearly established that it gave a considerable benefit over a cheaper alternative so I very much value your research.

[jimthompson]

Greetings All,

 

Sorry for the delay but I finally had a chance to use my Ocean Optics USB4000 UV-VIS spectrometer to measure the spectral response of the five sample tri-band filters I have.  I have posted screen captures of the resulting plots to the same album on Flickr as the images I posted at the start of this thread. 

 

https://flic.kr/s/aHsmHLdaJ4

 

I found that the OPT Radian Triad and STC Duo-Narrowband both had measured spectral responses quite different than what their marketing material indicated, the marketing plots both being rather idealized and not based on actual measurements.  The other three filters match their marketing plots rather well.  The Omega Optics brand filter was especially interesting since the measured spectrum of the filter I got in 2014 and the one I purchased new just this Summer 2019 both line up with their marketing data very well.  One more note on the OPT Radian Triad filter; it has the narrowest pass band at Halpha of all the filters tested, but that pass band is also shifted a little bit to the left of 656nm.  I suspect that this observation means that the OPT Radian Triad filter is less compatible with fast focal ratio optics than the other filters.  I will look into some sort of test to see if I can evaluate f-ratio sensitivity.

 

My next step is to take all my test results, including some I haven't presented yet, and write them up in a report.  Btw, I just learned that ZWO has their own tri-band filter now, so I have one on the way to me now to be added to the review.  If you have any questions about these results, let me know.

 

Best Regards,

 

Jim T.

[highfnum]

Omega Optical Hydrogen & Oxygen Nebula LPF Improved

 

I have that one 

works very well 

i posted some images on other thread

[selfo]

Hey Jim:

 

Looking forward to your review.  Your previous summery of various filters and their effects were very helpful to me in understanding how to use these game changing tools when I ventured into EAA.  Presently the only narrow band filter I use is the Omega DGM Narrowband nebula filter which while giving me very good results I would think there are better options now.  As you implied paying 1K for a filter I would expect a very substantial increase in performance over what I currently use. 

 

Stewart 

[BigBanger]

Hi Everyone,

 

I am sure some of you have heard about or are already using one of these new narrow tri-band filters.  Perhaps the most popular ones are the OPT Triad and the Optolong L-eNhance.  What you maybe did not know is that these filters are not actually all that new.  They have been around since 2012 but have only really taken off in popularity in the last year or so.  There are presently five commercially available versions of this type of filter:

 

- OPT Radian Triad

- STC Dual Narrowband

- Optolong L-eNhance

- Astro Hutech IDAS-NB1

- Omega Optical Hydrogen & Oxygen Nebula LPF Improved

 

I have procured a sample of all five filters, and am in the midst of testing them.  As usual I will publish a test report when I am done, but in the meantime I thought I'd share some of my preliminary results with everyone.  You can view my test captures to date at the Flickr link below. My next step is to measure each filter's response with my spectrometer.

 

https://flic.kr/s/aHsmHLdaJ4

 

Cheers,

 

Jim T.

 

Thank you, Jim... Your testing and reporting has been most useful for me. Based on your results I ordered the L-eNhance filter for my ZWO ASI183MC Pro OSC camera.

[jimthompson]

Thank you, Jim... Your testing and reporting has been most useful for me. Based on your results I ordered the L-eNhance filter for my ZWO ASI183MC Pro OSC camera.

I'm glad my work has been helpful.  I agree that the Optolong offering is a very good value choice:  a high level of performance at a reasonable price.

 

Cheers,

 

Jim T.

[GTom]

Thank you Jim, brilliant work. I live in a light polluted area, where an efficient tri-band filter would restore the usefulness of DSLR/any color sensors. I wonder about the importance of SII, as some filters exclude the 672nm.

[jimthompson]

Thank you Jim, brilliant work. I live in a light polluted area, where an efficient tri-band filter would restore the usefulness of DSLR/any color sensors. I wonder about the importance of SII, as some filters exclude the 672nm.

When using individual narrowband filters and then combining after to make a colour image, I think it is possible to pull out some really interesting details in SII.  But in the application we are talking about, using a one-shot-colour camera, any SII that is coming from a target will be very small compared to the Halpha component.  I don't think you'd ever notice the SII missing in that situation.  Emissions from Halpha are just so much stronger than anything else, except perhaps O-III.

 

Cheers,

 

Jim T.

[astroseyer]

Very interesting and detailed. Thanks for sharing. The price point for ZWO in comparison seems like a good investment, to me.

[tedswanson]

Has anyone seen harsh color gradients when using these types of filters with the ASI294?  I have the ZWO Duo-Band filter and it's creating a lot of work for me in processing to remove the red to green color cast from one side to the other.  I'm thinking of switching to the Optolong for this reason.  It's in the flats and the lights.  When I rotate the filter the gradient moves with the rotation.

 

Just curious if this is a known characteristic of these filters or if I should do a lot more troubleshooting.

 

Edited by tedswanson, 14 December 2019 - 12:37 PM.

[DSO_Viewer]

Has anyone seen harsh color gradients when using these types of filters with the ASI294?  I have the ZWO and it's creating a lot of work for me in processing to remove the red to green color cast from one side to the other.  I'm thinking of switching to the Optolong for this reason.  It's in the flats and the lights.  When I rotate the filter the gradient moves with the rotation.

 

Just curious if this is a known characteristic of these filters or if I should do a lot more troubleshooting.

 

Triangulum.jpg

You don't say what type of filter you're using? Here is a good recent Youtube showing different filter in light polluted areas using OSC's.

 

https://www.youtube....h?v=hFq-y8wTp9o

 

Steve

[tedswanson]

Sorry - meant to say that I have the ZWO Duo-Band filter that Jim reviewed.  Great video though.  Trevor has a lot of this figured out for sure.

[jimthompson]

Has anyone seen harsh color gradients when using these types of filters with the ASI294?  I have the ZWO and it's creating a lot of work for me in processing to remove the red to green color cast from one side to the other.  I'm thinking of switching to the Optolong for this reason.  It's in the flats and the lights.  When I rotate the filter the gradient moves with the rotation.

 

Just curious if this is a known characteristic of these filters or if I should do a lot more troubleshooting.

 

Triangulum.jpg

Hi Ted,

 

You are not alone in observing the odd colour gradient when using filters with the ASI294.  I have encountered the same issue with my ASI294, and have heard reports from other users of this camera as well.  It seems to be a problem unique to this particular camera.  In the limited time I had to evaluate the Touptek camera that uses the same sensor, I did not encounter this phenomenon, so I believe it is a problem particular to the ZWO camera with IMX294 sensor.  The severity of the colour gradient varies with the specific filter you are using.  If you check out some earlier filter testing I did using the ASI294 you can see what I mean:

 

https://flic.kr/s/aHsmGkDPiX

 

In the images from that particular test, the images captured using the Astronomic UHC and Meade Narrowband filters have a particularly severe gradient, but other filters do not.  The presence of the gradient has something to do with how the gain is applied to the red and blue channels in the camera when you use those settings to set your white balance.  It does not seem to be related to how narrow the filter is, but how the pass bands are arranged and thus the resulting white balance.

 

In my testing I did see some gradients using the OPT Radian Triad and STC Duo Narrowband filters, but I believe those gradients were due to my filter samples being 1.25", where all the others are 2".

 

Cheers,

 

Jim T.

[tedswanson]

Hi Ted,

 

You are not alone in observing the odd colour gradient when using filters with the ASI294.  I have encountered the same issue with my ASI294, and have heard reports from other users of this camera as well.  It seems to be a problem unique to this particular camera.  In the limited time I had to evaluate the Touptek camera that uses the same sensor, I did not encounter this phenomenon, so I believe it is a problem particular to the ZWO camera with IMX294 sensor.  The severity of the colour gradient varies with the specific filter you are using.  If you check out some earlier filter testing I did using the ASI294 you can see what I mean:

 

BINGO!  That's exactly the color gradient I'm seeing.  I'm actually happy to hear that it's not the filter because that would have meant a lot of returning and testing of filters without any improvement.  I'm "stuck" with the 294 and I really do like it, but I'm wondering if there's any way to mitigate the issue or if it's just something that needs to be dealt with in post-processing.  If so, what's the best way to do that without sacrificing the image?

 

Also, did you experiment with moving the filter closer to the sensor?  I can't recall if you said where the filter resides in your imaging train.  My filter is all the way at the front - furthest from the sensor.  Not sure if that makes a difference.  Moving it closer would require a filter wheel since these filters tend not to have a female thread.

[DSO_Viewer]

BINGO!  That's exactly the color gradient I'm seeing.  I'm actually happy to hear that it's not the filter because that would have meant a lot of returning and testing of filters without any improvement.  I'm "stuck" with the 294 and I really do like it, but I'm wondering if there's any way to mitigate the issue or if it's just something that needs to be dealt with in post-processing.  If so, what's the best way to do that without sacrificing the image?

 

Also, did you experiment with moving the filter closer to the sensor?  I can't recall if you said where the filter resides in your imaging train.  My filter is all the way at the front - furthest from the sensor.  Not sure if that makes a difference.  Moving it closer would require a filter wheel since these filters tend not to have a female thread.

I used the AstroFlat Pro plugin with Adobe Photoshop Elements on your jpeg m33 image and it did a pretty good job at removing the gradients while maintaining the details.  Here is the link if interested and it works as a plugin with several processing programs.

 

Steve

Edited by star drop, 15 December 2019 - 03:43 PM.

[LaCasaCorp]

My problems with the 294 mostly focused on bad reflections on bright stars coming from the interaction between filter and sensor window (other sensors were perfectly fine with the same filters), in particular with Baader filters.

I used several times the IDAS NB1 and I'm happy with the results. I'm imaging @F4, and scope F ratio could easily have an impact on those gradients. Filter location should be relevant as well, because the light will interact with the the filter differently if it's located before or after focal reducers... I would try to place the filter as close as possible to the sensor, maybe with a filter drawer or, if you have 1.25" filters, with the little adapter from zwo that let's you thread the filter inside the first 11mm female-female ring, that is normally mounted right in front of the sensor body. 

 

 

BINGO!  That's exactly the color gradient I'm seeing.  I'm actually happy to hear that it's not the filter because that would have meant a lot of returning and testing of filters without any improvement.  I'm "stuck" with the 294 and I really do like it, but I'm wondering if there's any way to mitigate the issue or if it's just something that needs to be dealt with in post-processing.  If so, what's the best way to do that without sacrificing the image?

 

Also, did you experiment with moving the filter closer to the sensor?  I can't recall if you said where the filter resides in your imaging train.  My filter is all the way at the front - furthest from the sensor.  Not sure if that makes a difference.  Moving it closer would require a filter wheel since these filters tend not to have a female thread.

 

[tedswanson]

I used the AstroFlat Pro plugin with Adobe Photoshop Elements on your jpeg m33 image and it did a pretty good job at removing the gradients while maintaining the details.  Here is the link if interested and it works as a plugin with several processing programs.

 

https://www.prodigit...tPro1_News.html

 

Steve

That's a pretty cool tool.  Do you think it's better than Gradient XTerminator?

[tedswanson]

My problems with the 294 mostly focused on bad reflections on bright stars coming from the interaction between filter and sensor window (other sensors were perfectly fine with the same filters), in particular with Baader filters.

I used several times the IDAS NB1 and I'm happy with the results. I'm imaging @F4, and scope F ratio could easily have an impact on those gradients. Filter location should be relevant as well, because the light will interact with the the filter differently if it's located before or after focal reducers... I would try to place the filter as close as possible to the sensor, maybe with a filter drawer or, if you have 1.25" filters, with the little adapter from zwo that let's you thread the filter inside the first 11mm female-female ring, that is normally mounted right in front of the sensor body. 

I'm definitely going to try moving it closer.  Even taking off the extension in the front of my imaging train which moved the 2" filter back towards the sensor about an inch seemed to help.  I'm going to trade the 2" sensor in for a 1.25" sensor and see if putting it right in front of the sensor helps.  Until then, AstroFlat definitely seems to take care of the problem in processing.  Thanks, everyone!

[DSO_Viewer]

That's a pretty cool tool.  Do you think it's better than Gradient XTerminator?

Sorry, I cannot answer that since I have never used Gradient Xterminator. Is this also a plugin for Photoshop Elements, I do not have the regular Photoshop

 

Steve

[tedswanson]

Sorry, I cannot answer that since I have never used Gradient Xterminator. Is this also a plugin for Photoshop Elements, I do not have the regular Photoshop

Steve

Yes, it’s a Photoshop plug-in, but I just tested both and I like AstroFlat a bit better.