Compose question

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Burly
Posts: 381
Joined: Mon Aug 31, 2015 7:06 am
Location: Northamptonshie uk

Compose question

Post by Burly »

Hi help /guidance required, I have 10 hrs data using an LExtreme filer with a zwo533mc and about 4 hrs using zwo533mc with a S11 filter (yes I know not the best way ) using compose what algorithm would I choose if wanting to see if I can get a SHO image assuming sii as red ha as geeen and o111 as blue but unsure what algorithm to choose .

Dave
Stefan B
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Joined: Sat Oct 31, 2020 8:59 pm

Re: Compose question

Post by Stefan B »

Hi Dave,

I guess you'll have to split your l-extreme stack into Ha and OIII (e.g. just load l-eNhance into red, leave green and blue empty and save...thus you isolated Ha in a separate file). Then simply load SII in red, Ha in green and OIII in blue. Then you can continue as it was a regular SHO composition.

At least that's how I'd try it.

Regards
Stefan
Mike in Rancho
Posts: 666
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: Compose question

Post by Mike in Rancho »

Hi Dave,

Yes I have done the same thing. :D What is your stacking solution? ST and DSS can do it, but I like involving ASTAP or Siril too for file extractions as they are pretty easy to use and maintain 32-bit data.

The way I went about it was this -- use Siril or ASTAP to extract separate R, G, and B files from both the L-eXtreme and SII stacks. Name them so you know what they are. For the SII you only care about the R, the other extractions can be deleted. Call that R your SII file. Then do the same with the L-Extreme but keep all channels. The R you can name as your Ha.

At this point I would use ASTAP or DSS to register all four files - SII, Ha, and the G and B from L-eXtreme. ASTAP has a "cal & align only" option that will spit out aligned files. In DSS you would turn on save aligned intermediate files (and discard any resulting autosave).

The G and B from your L-eXtreme need to be combined into one. You can use ST composition for this and take advantage of how ST can bump it up for 2xG. Load the appropriate extractions into G and B channels, and pick a bicolor (GB)(GB) solution, mono. I think (?) interpolation should be off but remain unsure (and might not make a big difference anyway). Again if you want I believe you can also take advantage of one of the 2xG OSC solutions due to better SNR in the green. This mono file can get saved off as your OIII.

Now you can composite as S, H, and O. There will almost certainly be some cropping of the overlap errors required. Also, you might want/need to run separate Wipes on each channel, save the linear file, and then composite those. All depends on the data, but SII (due to relative weakness) and OIII (due to the bandpass) can sometimes need strong Wipe, whereas the Ha is clean and you wouldn't want to apply the same aggressiveness. But I've had it turn out good either way.

I think the last time I did this was in February. Hopefully I haven't forgotten anything!
Burly
Posts: 381
Joined: Mon Aug 31, 2015 7:06 am
Location: Northamptonshie uk

Re: Compose question

Post by Burly »

Thank Mike and Stefan I will look into this once clouds roll in I have about 16hrs of duoband data and 4hrs s11 which probably isn’t enough to make much difference.

Dave
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