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Old 18-01-2021, 06:59 AM
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The_bluester (Paul)
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Duoband filter users - request for example subs

I am thinking about giving a duoband filter a try with my ASI2600. In my case not to combat light pollution, more to see what the output is like if the debayer routines in Astro Pixel Processor aimed at NB filters on OSC cameras are used.

In APP there are debayer routines which pick apart the OSC data and construct mono images for HA, or OIII and so on, I am interested to see if it can dice up an image sub shot with a duoband and produce separate HA and OIII integrations that look worthwhile.

Would anyone using a duoband be prepared to send me a handful of subs on the same target (Even better if you are using an ASI2600MC like me) so I can try out the debayer algo's deduicated to that in APP and see what the outcome is?
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Old 18-01-2021, 09:29 AM
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multiweb (Marc)
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Depending on the bandpass of the peaks in your filter spectrum if you shoot with an OSC you'd debayer to individual channels then stack them separately to extract the Oiii and the Ha. Ha is likely to be in the red pixels and Oiii in both green and blue pixels. Or if you're adventurous you could heavily dither your data then take advantage of the bayer drizzle process in PixInsight straight to color then do a drizzle integration. For the latter to work correctly you'll need to increase the number of individual subs even if you use the same total integration time. I haven't used the duo band filter I have yet with an OSC but will do in the near future so I'll let you know how that goes. To date I have only shot mono with it with some success.
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Old 18-01-2021, 09:49 AM
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I have also been given a damaged HA filter (Arrived damaged in transit) so I am going to give that a try. It arrived with a crack in it but it is a 2" filter and I am using an APS-C sensor so if I am lucky the crack will be out of sight. I guess flats will tell me if I am that lucky. Either way it will be an interesting experiment to see how the camera responds.

The plan is to go mono eventually so if either NB or dual band work well I may buy one of either plus a filter wheel and a lum filter (to keep things parfocal) to get some of the NB benefit while spreading the cost of gear out (And automating filter changes) understanding of course that a dual band filter will become useless if I go mono.

APP has some specific debayer algos for NB or dual band with an OSC so it will be interesting to try them out.
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Old 18-01-2021, 09:58 AM
Startrek (Martin)
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I use a ZWO Duoband filter with my 2600MC during Moon phase or when in Sydney under Bortle 8 skies
The subs from the 2600MC which are huge files are stacked in DSS ( I choose Bilinear Interpolation for transformation algorithm) and RGB is left untouched. Stacked file is pure and linear data which Startools needs
I process in Startools V 1.6 which which has a Compose module specifically for OSC narrowband ( Duoband or tri and or quad band data )
It starts out in synthetic luminance ( mono ) for the majority of your workflow then once you hit the colour module it gives you endless combos and options for narrowband colour processing , a delite to use. I believe V1.7 is even better
Ivo Jager the developer of Startools has made it so easy now to process NB data , great support too !!
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Old 18-01-2021, 10:04 AM
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The_bluester (Paul)
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In my case what I am hoping to be able to do is gain the ability to pick out some HA and OIII data, as a step along the road to full LRGB-NB imaging.

It was quite a bit of work but one thing I have done in the past in APP was to save calibrated files as seperate R-G-B files then integrate the colours seperately, then finally combine them as an RGB image as you would for LRGB imaging. It did seem to provide an improvement but adds a fair bit to the workflow.
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Old 18-01-2021, 11:22 AM
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Hi Paul,

I use a ZWO 071MC with the STC Duo filter. I’ve just gotten into using the APP band separating to extract Ha and O3. It takes a lot longer to do but I can say it’s definitely worth it. I reintegrate in Photoshop to create a HOO image it it works really well and makes post processing much easier.

As far as sharing subs goes, I’d be happy to but as has been mentioned they are quite large and perhaps could only be done by USB maybe ? Happy to help if you want to go down that avenue ?

Cheers

Ryan
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Old 18-01-2021, 11:33 AM
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Usually I deal with anything large files with using Wetransfer. The free version I think you can send up to 1 gig at a time. Even just a handful of files would be interesting to play with.

One question I was about to post to the APP forum was how to deal with darks and flats. I am not sure if they have to be debayered with the same algo as the light frames. I presume flats would but I don't know about darks.
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Old 18-01-2021, 11:48 AM
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No worries. I’ll see what I can do. If you can PM me your email address ? Or what ever address it is that I need to send it to ?

As far as darks and flats go ( as far as I can tell because I’m newish to it too ) is that it debayers all of your files but only applies the appropriate channel of each calibration frame when calibrating if that makes sense ?
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Old 18-01-2021, 12:39 PM
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I have PM'd you an email address. No rush on it, I am just looking to see how the data goes. You have not got data on M42 do you? I could probably blend that in APP with the data I already have.
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Old 18-01-2021, 05:11 PM
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Quote:
Originally Posted by The_bluester View Post
I am thinking about giving a duoband filter a try with my ASI2600. In my case not to combat light pollution, more to see what the output is like if the debayer routines in Astro Pixel Processor aimed at NB filters on OSC cameras are used.

In APP there are debayer routines which pick apart the OSC data and construct mono images for HA, or OIII and so on, I am interested to see if it can dice up an image sub shot with a duoband and produce separate HA and OIII integrations that look worthwhile.
My personal opinion based on non-scientific comparisons of the output from APP when debayering in "Adaptive Airy Disk" vs "Ha-Oiii Colour" is basically identical, assuming the same data is fed in. I have never been able to see any difference whatsoever when feeding in my subs from an OSC with Optolong L-Enhance and L-Extreme. If you use the "Extract Ha" or "Extract Oiii" algorithms, Extract Ha should produce an identical result to what you'd get from the red channel of an image stacked with "Ha-Oiii Colour", whilst Extract Oiii seems to be the data from both the Blue and Green channels. Again, no scientific comparison has been done, this is just my observations.

In summary: the debayer algorithm selected matters little aside from the fact that Extract Oiii does combine the B/G data into a single file. You can debayer using the Ha-Oiii Colour or AAD algorithm and split the channels into R/G/B then use the RGB Combine feature to get a more-or-less identical result to what you'd get by using the Extract Ha/Extract Oiii algorithm and re-combining.

The output with a dual band filter will look very different to the same target imaged with a normal filter like UV/IR cut or something of course. I use my dual band filter even in dark (Bortle 2-4) skies sometimes as I prefer using the RGB Combine feature to edit, and sometimes I use UV/IR Cut as I prefer the broadband colours (eg M42)
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Old 18-01-2021, 08:21 PM
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Where I am interested in it is in being able to image in full OSC mode, then re image with either a HA or dual band filter and to be able to get a separate HA and/or OIII integration to layer in to the OSC data.

I popped the damaged 2" HA filter in the train today and shot some flats and I can't see any significant issues from the crack, so I am going to push on with it to experiment with how the camera goes gathering HA.

The only problem I have at the moment is that I have found so far, no one makes an unmounted 36mm duo band filter. I plan to go to mono down the track and want to be able to put whatever I put in front of it in a filter wheel, but in the duo band there seems to be 1.25" and 2" mounted options. 1.25" will almost certainly cause vignetting, and 2" would make for such an expensive exercise for the likes of Chroma or similar filter that I would do better in the long run to just buy 36mm unmounted HA, OIII and Lum (To keep it parfocal) to put in a 36mm filter wheel.

If I could be convinced that ZWO have sorted the halo issues they used to have on some of the NB filter then that would change things as it would make 2" filters affordable.
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