Hi,
spent some time on making a doppler image of an H-Alfa capture this morning with the Sol'Ex SHG. (before clouds spoiled the session)
Images generated with +3 /-3 pixel shift (0.59A) and then combined in a color image.
Maybe still need to work a bit on the technique, but not too bad ...
Regards,
Paul
Doppler Image Jan 30
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Doppler Image Jan 30
Last edited by PDB on Sun Jan 30, 2022 3:22 pm, edited 1 time in total.
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Re: Doppler Ilage Jan 30
Wow!! I like it I take it that red is red shift and blue is blue shift?
Alexandra
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Re: Doppler Image Jan 30
Hi Alexandra;
yes it is supposed to be like that, unless I accidentally switched colors. I took +3 px for red and -3px for blue.
The green channel is created by averiging the blue and red one.
Rgrds,
Paul
yes it is supposed to be like that, unless I accidentally switched colors. I took +3 px for red and -3px for blue.
The green channel is created by averiging the blue and red one.
Rgrds,
Paul
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Re: Doppler Image Jan 30
Looks great Paul!
http://brierleyhillsolar.blogspot.co.uk/
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Re: Doppler Image Jan 30
Hi Paul,
Interesting but I have to ask. What does this show ? I have seen the Dopplergramm posted in the SDO website but it looks completely different.
Thanks Rainer
Interesting but I have to ask. What does this show ? I have seen the Dopplergramm posted in the SDO website but it looks completely different.
Thanks Rainer
regards Rainer
Observatorio Real de 14
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North 22° West 101°
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Re: Doppler Image Jan 30
Hi Paul.
Nice dopplergram but I agree with Rainer that your version is different from the standard type of dopplergram from SDO. There are probably two reasons for this. One reason for the difference lies in your use of the green channel which contains the velocity averaged information whereas a true dopplergram simply uses the difference (red minus blue or vice versa). You are actually presenting a true dopplergram superimposed on a conventional image - which can be useful for correlating velocity fields with actual feature locations. The other reason is that your dopplergram is created in H alpha (chromospheric) while the SDO image (on the NASA site) is likely using a photospheric line (although I can’t find the information on the site).
Cheers.
Peter
Nice dopplergram but I agree with Rainer that your version is different from the standard type of dopplergram from SDO. There are probably two reasons for this. One reason for the difference lies in your use of the green channel which contains the velocity averaged information whereas a true dopplergram simply uses the difference (red minus blue or vice versa). You are actually presenting a true dopplergram superimposed on a conventional image - which can be useful for correlating velocity fields with actual feature locations. The other reason is that your dopplergram is created in H alpha (chromospheric) while the SDO image (on the NASA site) is likely using a photospheric line (although I can’t find the information on the site).
Cheers.
Peter
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Re: Doppler Image Jan 30
Thank you for the comments Peter. I did several tries (also with 2 channels) but could not get good results (probably combining the wrong way) So I switched to what is descrived on the Sol'Ex page from Christian Buil) using an average of the 2 channels as green channel.
Regards,
Paul
Regards,
Paul
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Re: Doppler Image Jan 30
Hi Paul.
You’ve probably done this already, but why not try different pixel shifts and see if you can intensify the structure in the dopplergram? As you progress outwards from line centre you are “tuning” to faster velocities and these higher velocities might prevail near the active region.
Cheers.
Peter
You’ve probably done this already, but why not try different pixel shifts and see if you can intensify the structure in the dopplergram? As you progress outwards from line centre you are “tuning” to faster velocities and these higher velocities might prevail near the active region.
Cheers.
Peter
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Re: Doppler Image Jan 30
I’d recommend this paper, described by many as groundbreaking. It’s old and deals with film capture but it is relatively straightforward to “translate” into digital spectroheliography.
Velocity Fields in the Solar Atmosphere. I.
Preliminary Report.
Leighton, Robert B. ; Noyes, Robert W. ; Simon, George W.
1962ApJ...135..474L
https://ui.adsabs.harvard.edu/abs/1962A ... L/abstract
Regards.
Peter
Velocity Fields in the Solar Atmosphere. I.
Preliminary Report.
Leighton, Robert B. ; Noyes, Robert W. ; Simon, George W.
1962ApJ...135..474L
https://ui.adsabs.harvard.edu/abs/1962A ... L/abstract
Regards.
Peter