I had a request from a user of our spectroheliograph (SHG) reconstruction software https://github.com/thelondonsmiths/Solex_ser_recon_EN to summarise how I stack images from SHG scans. I put together some thoughts into a PDF document that is uploaded to our GitHub repository https://github.com/thelondonsmiths/Sole ... umentation.
I attach the document here (perhaps it better belongs in the Solar Reference Library). The data is from observations made on Aug 11 viewtopic.php?t=37552
Spectroheliograph stacking workflow
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Spectroheliograph stacking workflow
Last edited by thesmiths on Thu Sep 22, 2022 2:07 pm, edited 1 time in total.
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Re: Spectroheliograph stacking workflow
Douglas, very interesting and useful tutorial.
A question: what is the maximun offset and images you can extract with your 3.5 software?
I tried -10:10 in total 20 frames,and is all OK. But if I try -30:30 (60 frames) the system seems not to work.
Did I miss something ?
Cheers
Fulvio
A question: what is the maximun offset and images you can extract with your 3.5 software?
I tried -10:10 in total 20 frames,and is all OK. But if I try -30:30 (60 frames) the system seems not to work.
Did I miss something ?
Cheers
Fulvio
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Re: Spectroheliograph stacking workflow
There should be no limit but I never tried more than -20:20. When you say it does not work, what do you mean exactly? Is your ROI wide enough to accommodate such a range? I suspect if the spectral line is only 20 pixels away from the border and you ask it to do 30 pixels, it might not like it. If there is significant "smile" or "tilt" in the system, that will also reduce the distance to a border.fulvio.mete wrote: ↑Thu Sep 08, 2022 8:01 am what is the maximum offset you can extract with your 3.5 software?
I tried -10:10 in total 20 frames, and is all OK. But if I try -30:30 (60 frames) the system seems not to work.
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Re: Spectroheliograph stacking workflow
Douglas, the Halpha line in my instruments is from 50 to 60 pixels wide,in a ROI with a overexposed continuum, depending on the gamma and the other settings of acquisition software.The real extension of the line is 60 pixels (1.2 A, considering the dispersion of 0.02 A/pixel of the instrument) .When I tried -30:30,(obviously with a 60 pixel line) there was neither response , nor image.May be I miss something.In SLM many times I get 56 or 61 frames of 1 pixel each with no problems.Anyway, I'll try to make a test with INTI AVI recon 3.5 with exactly the number of pixels of the dark part of the line, from the blue to the red.
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Re: Spectroheliograph stacking workflow
Using SLiM is a manual process so you can visually see how close to the border you are, taking into account both "smile" and "tilt". Our software is automated so you will need to give it more room if you want to use it totally automatically.fulvio.mete wrote: ↑Thu Sep 08, 2022 5:00 pm In SLM many times I get 56 or 61 frames of 1 pixel each with no problems.
If you want to maximise the amount of offset, you can do a safe range like '-25:25' and then do the other ones semi-manually; e.g. '26,27,28,28,30' and then '-26,-27,-28,-29,-30'. That way, the process will likely fail at some point, but it will towards the end of the processing, not the beginning.
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Re: Spectroheliograph stacking workflow
Thanks for quick reply, Douglas, and the suggestions: I'll do it.
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Re: Spectroheliograph stacking workflow
This morning I was able to stack 50 frames (-25-25) with no problems.I was careful to cover a few pixels less the the width of the line, and this work very well.