Solar Observing – Mono to Colour

Forums Sun Solar Observing – Mono to Colour

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    Adam Rawlinson

    Hello fellow observers.
    Been in the BAA a long time but not connected with the forums much (sorry) or gallery before.
    I am hoping you can help me. Hopefully this is in the right forum (I toyed with imaging – but this is more solar related)

    I have recently purchased a totally excellent LuntLS50Tha scope with B600 filter.
    I have been observing and imaging using my normal scope, so solar imaging is new to me
    Using a monochrome camera (PlayerOne – Neptune -M) get some amazing results. Incredinle definition

    I have also found that if I use the Astroart package (my long term favorite) I can convert the mono data image to colour data format which then allows me to use colour curves and balancing.
    Apart from “colourising” the image to make it more visibly attactive, I have found that the RGB colour data is assigned across the passband of the Hydrogen Alpha image. (remember it started as a mono image and the ADU values at a particular point represent intensity)
    So this then introduces the tantilising concept of different RGB values for different sample points across the narrowband spectrum.
    So this in turn implies that the “colour” now become frequency (or wavelength …. whichever you think in) linked.

    So this is the quardry I have. Within the narrowband Ha emission there is variance here – which coudl reasonably be attributed to dopplar shift in the radation from the photosphere and chromasphere (in the edge on profiles)
    Another interpretation is that it might be indicating temperature…..

    Or…. is this simply an interesting and fortuetous processing anomaly?

    Idea / advice welcome

    Adam Rawlinson

    Andy Wilson

    Hi Adam,
    Welcome to the BAA Forum! That sounds like an excellent telescope and those are great images.
    I am not sure I understand your question, but I’ll have a go at an answer.
    With colourising I would be surprised if the algorithm in Astroart does anything other than assign predetermined colour values in RGB based on intensity to make it look nice, rather than anything to do with velocities. It is possible it has a template for the Sun, and varies the colour based on the location on the solar disc. The key point is the monochrome pixel values contain no data that can be converted into a velocity. I expect the temperature has nothing to do with it, other than cooler parts of the Sun such as sunspots emit less light.
    All this said, if you are able to tune the H-alpha pass band in your telescope, then you might be able to sample different velocities relative to the H-alpha rest wavelength.
    Best wishes,

    • This reply was modified 1 year, 7 months ago by Andy Wilson.
    Adam Rawlinson

    Thanks for the reply
    No, Astroart isnt doing anything clever. Its just spreading the RGB simulated channels across the visible image histogram. So using the histogram if i tweak the blue channel down then the central disk (becomes more defined as is overexposed in unstretched image) and likewise those prominences are all in the red channel (as transferred across from the mono image)
    Its a 16bit image so loads of scope to tweak.

    Im doing a BSc in Astronomy and have literally just started a heavy Solarastrophysics module. Trying to put it all into context with what can be seen.

    The visible radiation from particle does technically display doppler effects (due to speeds of the material outflow) but yeah… .logically the mono chip (a Player One Neptune-M camera) sampling must be catching the whole passband if i think about it.

    I have indeed tried tweaking the pressure passband adjustment and yes, have some images at different values. I shall have a play and see where it leads me!

    Thanks again for coming back to me


    Andy Wilson

    Good luck with the BSc. Exciting times!
    Best wishes,

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