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Technical Aspects of the Triad Ultra Filter

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#1 johnsoda

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Posted 31 January 2019 - 03:08 PM

I'm starting a new topic to discuss this filter.  It will concentrate on rational and constructive discussions of its advantages and disadvantages and people's actual experience with the filter, not conjectures, criticisms of how people spend their money, off-topic examples of wonderful work you've done, or blind bashing.  I'll start with something started on another thread, which is reasonable expectations of what you might be able to do with the filter, given previous narrowband experience.  I showed an image containing Halpha and OIII information on the Crescent Nebula, with the two narrowbands done separately, as an example of what you might be able to do with the Triad simultaneously.  A legitimate question was raised about whether the two channels were stretched separately and then combined. 

 

I went back and looked at some more recent imaging work I did on the Crescent Nebula.  Here is the Halpha channel info (56 X 300 sec.), stretched using Histogram Transformation in PixInsight:

 

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Here is the OIII channel (49 X 300 sec., so it's actually ~13% less integration time), stretched using the exact same settings in Histogram Transformation:

 

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Click on the small images for better images and more information.

 

Now, the OIII is somewhat dimmer.  However, I think you'll have to agree that they are certainly of the same order of magnitude of brightness, and I think they would look fine combined together, either in quasi-real-time (not possible using separate filters) or in processing, where you could stretch the OIII a bit more.  Certainly, the difference is no worse or better than what you might see between LRGB filters.  Keep in mind with the Triad, it would be one set of lights, one filter, one set of flats, one focus point, no filter wheel, and much simpler processing.  It also opens up the possibility of multi-narrowband EAA.


Edited by johnsoda, 31 January 2019 - 03:15 PM.

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#2 lucam

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Posted 31 January 2019 - 03:55 PM

Unfortunately, as  I am sure you know, the Crescent Nebula is more the exception than the rule in balanced relative intensity of Ha and OIIi. Try imaging the Jellyfish Nebula (IC 443), which has much weaker OIII and SII relative to Ha. If the Triad filter is able to get the three lines out in a balanced way, that's a good feat! Another way to look at it is that with the Crescent, in PI you can run channel combination in the linear state (perhaps using Linear Fit to balance the channels). Many narrowband targets have to be combined in the non-linear processing phase to balance the emission lines. I can see the appeal of the filter and there is no doubt an element of convenience and immediate feedback that is hard to deny.

 

Looking forward to hearing more about your experience and seeing what images you can pull off! 



#3 johnsoda

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Posted 03 February 2019 - 11:01 AM

Okay, in between some dew/frost and other issues, I was able to do some more imaging with the Triad Ultra, albeit not as much as I wanted.  For the following, click on the little images for better images and acquisition details.  Here is the result, with channels stretched the same:

 

get.jpg?insecure

 

Here are the separate channels, stretched the same:

 

R

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G

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B

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As expected, the R channel is dominant for this particular target and, probably, most targets of interest.  Of course, you can stretch each channel separately, with the attendant effect on noise:

 

get.jpg?insecure

 

Okay, let's go back to the first image:

 

get.jpg?insecure

 

Remember that this was done with one focus point, one filter, no filter wheel, a single set of lights, unguided, a single set of flats (actually, I didn't do flats, although I don't think that affected the image quality in this case noticeably), and very simple processing.  Could I do as well or better with my set of Astrodon narrowband filters?  Probably, although frankly I'd be hard put to do so in less than two hours of integration time.  This is why this filter is a game-changer for me and probably for many others; simplicity and very nice results quickly. 


Edited by johnsoda, 03 February 2019 - 11:03 AM.

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#4 johnsoda

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Posted 04 February 2019 - 08:24 PM

Did a little more imaging last night.  Did knock down the noise a bit, but whether it's that much better is a matter of taste.

 

get.jpg?insecure

 

Anyway, I've realized I bought this filter at the wrong time.  Wish I'd had it a few months ago, but we're heading into galaxy season now, and it's not particularly useful for that.  

 

I'd like to summarize what I think are the disadvantages and advantages of the filter, especially as compared with doing narrowband with separate filters and a mono camera.

 

Disadvantages:

 

  • Biggest is probably the loss of resolution.  For example, you are getting 1/4th the red pixels you'd have with a mono and filters for a similar camera, and red is the most important color in most cases.  I would argue that you can recover some of this through good dithering and CFA drizzling, but it is undoubtedly an issue.  On the other hand, as a worst case, is 2328X1760 pixels, as I would get from red pixels on my ASI1600MC, really that bad for most practical uses? 
  • There is a small loss of signal due to the Bayer filter itself, but, as discussed in the other thread, this is often exaggerated for modern astrocameras, as opposed to DSLRs.
  • With optical systems that not well color corrected, focus is going to be a compromise, whereas with the individual filters, focus can be adjusted for each color.  My guess is that this will be a problem with my camera lenses, although I haven't used the filter with them yet.  With apochromatic refractors, this shouldn't be an issue, and I haven't found it to be so.  Stars are consistently sharp throughout the spectrum.
  • Inability to vary exposure times for the various bands due to different signal strengths.  Obviously, you're always getting the same exposure times for all narrowbands with this filter.  This is a serious issue if you want equally "bright" exposure for the various bands.  You can stretch the channels separately, but this creates noise issues.  Frankly, this might be the only reason I might use my single narrowbands in the future on certain targets. 

Advantages:

 

  • Biggest is simplicity.  As I mention above, you can get very good results with one filter, no filter wheel, one set of lights, one set of flats, simple processing, and one focus point (with the caveats above).  This not only make things simple - it makes the process faster.  It also gets more people involved in astrophotography, which is a good thing for all of us.
  • Disk space.  Having multiple sets of flats and lights, one for each filter, starts to really add up.
  • Cost - this is going to make people laugh, I'm sure.  However, compared to my set of Astrodon narrowbands and filter wheel, this filter is much cheaper.  I'm sure I'll get arguments that you don't need Astrodons, but I would argue that any set of filters worth having, and possibly buying a mono camera if you don't have one, will be much more than the cost of this filter.
  • Speed in autofocus and platesolving - a surprise for me is how short my exposures can be for autofocusing and platesolving, compared to one narrowband.  I think this is because starlight comes from four different narrowbands with this filter, and stars are all you care about for autofocus and platesolving.  My autofocusing and platesolving exposures with this filter are the same binning and exposure time as I use for Lum or no filter.

If you have a good color astrocamera and want to get into narrowband work, I would seriously look at this filter.  Even if you have have narrowband filters and a mono camera, you might be interested.  I'm not sure how much use my single narrowband filters are going to get in the future.  Frankly, this filter is a lot more fun to use.


 

 


Edited by johnsoda, 04 February 2019 - 09:00 PM.

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#5 johnsoda

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Posted 10 February 2019 - 11:48 AM

Some more work with the filter.  I decided to go to a higher gain, but not too high - unity gain for the sensor.  Acquisition details and a better image available by clicking on the small image.

 

get.jpg?insecure

 

 

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#6 johnsoda

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Posted 10 February 2019 - 02:09 PM

File this under "interesting" rather than "aesthetically pleasing".  After I went to bed last night, I had SGP switch over to M101 after the Horsehead et al. became too low.  Halpha areas in galaxies have always fascinated me, but it's obvious I'll need a lot more integration time for this kind of work.  Click on the image to get the full effect of the noisy image and acquisition details.

 

get.jpg?insecure


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#7 jgraham

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Posted 10 February 2019 - 07:27 PM

Wonderful! I am also planning on using the Triad to explore Ha regions of galaxies. There are some regions in M33 that I am particularly interested in, but that will have to wait until next year.

 

Thanks for starting a new thread!



#8 jgraham

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Posted 10 February 2019 - 07:30 PM

There is some interesting information is this thread on extracting bicolor data from Triad images and then process that using more traditional bicolor techniques...

 

https://www.cloudyni...t-triad-filter/



#9 jgraham

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Posted 10 February 2019 - 07:31 PM

 NGC 2264 Complex in Monoceros – ZWO ASI071MC Pro & Triad Ultra
Telescope: Meade SN8 at f/4, Orion Atlas EQ-G, Baader Mk III MPCC
Camera: ZWO ASI071MC Pro, -10C; Gain: 200
Filter: 2” OPT Triad Ultra filter
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 18(of 44)x240sec saved as FITS
Darks: 32x240sec saved as FITS
Flats: 48x60sec using an LED tracing tablet with 3 layers of muslin
Average Light Pollution: Red zone, poor transparency, haze
Lensed Sky Quality Meter: 18.0 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

 

NGC 2264 (2-9-2019)-1j.jpg

 

I was hoping for a clear night, but it turned quite variable with a fair amount of passing haze and thin clouds. I selected the best 18 of 44 subs for this image. It turned out surprisingly well given the conditions. Comparing this with an earlier image shows that I will get much better star shapes without the MPCC on this scope (it was left on from an earlier session with my 6” f/5 Newtonian). Ugh. Soooo, there is plenty of room for improvement and I feel that this combination of scope, camera, and filter are going to work very well together.

 


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#10 jgraham

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Posted 10 February 2019 - 07:35 PM

M97 – Planetary Nebula in Ursa Major – ZWO ASI071MC Pro & Triad Ultra
Telescope: Meade SN8 at f/4, Orion Atlas EQ-G, Baader Mk III MPCC
Camera: ZWO ASI071MC Pro, 0C; Gain: 200
Filter: 2” OPT Triad Ultra filter
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 63x240sec saved as FITS
Darks: 32x240sec saved as FITS
Flats: 48x60sec using an LED tracing tablet with 3 layers of muslin
Average Light Pollution: Red zone, fair transparency, high humidity
Lensed Sky Quality Meter: 18.5 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

 

M97 (2-3-2019)-1j.jpg

 

This is an example of Hb/OIII target. Prior experience with my original Triad showed that these tended to turn out a tad green. The Triad Ultra seems to do a much better job discriminating the Hb and OIII giving much better color. I’ll know more after I have a chance to try this on other planetary nebula.

 


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#11 jgraham

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Posted 10 February 2019 - 07:38 PM

NGC 2237/44 – The Rosette in Monoceros – ZWO ASI071MC Pro & Triad Ultra
Telescope: Meade SN8 at f/4, Orion Atlas EQ-G, Baader Mk III MPCC
Camera: ZWO ASI071MC Pro, 0C; Gain: 200
Filter: 2” OPT Triad Ultra filter
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 44x240sec saved as FITS
Darks: 32x240sec saved as FITS
Flats: 48x60sec using an LED tracing tablet with 3 layers of muslin
Average Light Pollution: Red zone, fair transparency, high humidity
Lensed Sky Quality Meter: 18.5 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

 

NGC2239 (2-3-2019)-1j.jpg

 

So far this and the image of M97 are the only two that I have been able to take under reasonably clear skies. 

 


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#12 johnsoda

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Posted 13 February 2019 - 10:30 PM

Twenty minutes of worthwhile imaging tonight, but that was enough to confirm that, not surprisingly, this filter does not magically eliminate moonlight.  As you may know, the moon was very close to Orion tonight.  If I had more integration time, it would be worth it to get rid of the gradient.  In fact, I did just that, but for this data, the noise level was atrocious, and it's not worth playing around with.  Orion is fast disappearing as a target, for me, at least, but I hope to get one good night to do a better job.  Tonight was a good dry run in using the filter with a camera lens - first time for that.

 

raw_small.png


Edited by johnsoda, 13 February 2019 - 10:34 PM.

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#13 johnsoda

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Posted 13 February 2019 - 10:33 PM

Here's a half-hearted attempt at getting rid of the gradient, which is really all the effort this data deserves, given the moon, the lousy seeing, and the very short integration time.  However, as atrociously noisy as this is, and it is a great example of a noisy image, it does show the possibilities.  Imagine if I have all night and the moon is far away...

 

raw_dbe_small.png


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#14 johnsoda

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Posted 06 March 2019 - 11:17 PM

NGC 2174 with the Triad Ultra. 

 

get.jpg?insecure

 

F39F5652-13C8-4F9A-B97A-0A2D5746C212.jpeg

 


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#15 johnsoda

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Posted 23 March 2019 - 12:24 PM

Not a great time of year for this filter, but I did get this last night. Needs a lot more integration time, but that probably won’t happen until next year.  Click on the little image for acquisition details. 

 

get.jpg?insecure

 

C8A5F2ED-D155-4CF3-A53A-7203766D7D7D.jpeg


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#16 johnsoda

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Posted 30 March 2019 - 09:47 AM

Spent a little more time on the Seagull. 

 

get.jpg?insecure

 

 

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#17 johnsoda

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Posted 31 March 2019 - 08:28 AM

This will be a project over the next few months as the target moves into a better position for imaging, but here’s a start. 

 

get.jpg?insecure

 

76E5B9F7-15F8-47B1-B6D9-8CF1D0A62CAD.jpeg


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#18 Salty_snack

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Posted 31 March 2019 - 12:13 PM

This filter looks great and I plan on purchasing it sometime this year. Any thoughts on star colors through the triad ultra? I have an Astronomik UHC filter and star color is mostly red. I looks like reds and blues come through pretty well with the triad ultra.

I’m wondering if anyone has had combined broad band OSC with “narrowband” OSC images to keep good star color.

#19 johnsoda

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Posted 31 March 2019 - 12:34 PM

This filter looks great and I plan on purchasing it sometime this year. Any thoughts on star colors through the triad ultra? I have an Astronomik UHC filter and star color is mostly red. I looks like reds and blues come through pretty well with the triad ultra.

I’m wondering if anyone has had combined broad band OSC with “narrowband” OSC images to keep good star color.

Yeah, that’s another reason I wish they had a 36 mm version, so I could put it in my filter wheel and easily do Lum also. 



#20 Jeff2011

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Posted 01 April 2019 - 08:51 AM

"There is a small loss of signal due to the Bayer filter itself, but, as discussed in the other thread, this is often exaggerated for modern astrocameras, as opposed to DSLRs. "

 

Can't you counter act that by using the Triad with your mono camera to create a narrowband luminance that you can process into the data taken with your OSC.  When I read that this filter can be used this way it got my attention.  Sure it makes it a bit more complicated for both image capture and processing but I would be interested to see the results of this if you could try it.



#21 nateman_doo

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Posted 01 April 2019 - 09:49 PM

I was so happy to get the regular Triad filter, but everything looked so blue.  I have shelved it for the time being until I learn more photoshop and how to properly post process the images.  Also I feel this is best suited for emission nebula, not much else, but I will likely play around with it more in the future.   Love the discussions!  Keep them coming!



#22 nateman_doo

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Posted 03 April 2019 - 11:00 PM

I am imaging Pinwheel, and 600 seconds.  That galaxy should be beaming, but it so hard to see.  I have yet to take a single nice picture with this filter.  What am I doing wrong??

QHY-Triad-Ampglow.JPG

 

I know I have some HORRIBLE amp glow going on, and this random dark band across the sensor.  I mean I certainly cut down on the light pollution... but if I have to get subs that long that the amp glow looks like its almost physically damaging the sensor... then what am I doing wrong?

 

QHY 163C through an 8" R/C scope.  


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#23 premk19

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Posted 03 April 2019 - 11:09 PM

... then what am I doing wrong?

Imaging galaxies with a narrowband filter. Try imaging with just a plain UV/IR cut filter.


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#24 nateman_doo

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Posted 03 April 2019 - 11:11 PM

Here is a stack of 16 600 second frames with about 10 darks.  (flats just make it worst)

QHY-Triad-Ampglow.JPG

 

 

Here is what I did without the filter:

 NSvdFHmh.jpg


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#25 johnsoda

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Posted 19 May 2019 - 10:32 AM

I have a new camera, the ASI071MC Pro, that I'm using with my SV70T and the Triad.  I think this is a very good combination for narrowband.  Here are some initial results from a project I'll be working on over the next few months, especially during bright-moon periods.  I think I have the framing where I like it.  Overall, it looks good, although I do need to work on the field flattening.  Note especially the lower left corner.  It doesn't affect the overall aesthetics of the image much, but I think I can do better.  Click on the small image for acquisition details and a better quality image.

 

get.jpg?insecure

 

NA_small.png


Edited by johnsoda, 28 July 2019 - 07:57 PM.

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