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Thread: Taming bright stars

  1. #1
    mhorbacz's Avatar
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    Default Taming bright stars



    I am currently trying to process an image of the west veil nebula, and 52 Cyg is right smack dab in the middle. If I use a star mask, I still get halos around the star when I stretch the image. Is there another way of taming stars? Or is there a way to prevent these halos from occurring when using a star mask?
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    Default Re: Taming bright stars

    It's pretty hard to avoid haloes around bright stars. The halo is actual data that was recorded during the session, so anything you do to eliminate it will affect other objects.

    On my most recent image, Gamma Cassiopeiae ("Navi", magnitude 2.4) is right in the frame. My luminance data was taken with a Ha filter, which reduces star sizes quite a bit, but it was still big. Big enough that the star mask didn't even recognize it as a star. I had to create a custom mask just for Navi, using data from the blue filter. That allowed me to control it separately from the rest of the image.

    But you are really limited in what you can do, even with a mask. If you get too extreme, the bright star starts to look strange and unnatural. All you can do is to tone it down slightly and accept it as part of the image.

    Doing HaRGB imaging, I often get colour fringes around stars, because the stars in the colour layers are bigger than the stars in my Ha luminance layer. I have found that the best way to control them is to blend a little bit of luminance data from the colour layers into the Ha image. I have to be careful not to add too much or I lose those nice small stars, but it improves the coloured haloes considerably.

    Can you post your stacked and calibrated data in the Processing forum and see what people can come up with? You might get some good tips that way.
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    Default Re: Taming bright stars

    Do you mean just post a jpeg of the processed image? Or the entire tiff file?
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    Default Re: Taming bright stars

    Quote Originally Posted by mhorbacz View Post
    Do you mean just post a jpeg of the processed image? Or the entire tiff file?
    The TIFF file of the unprocessed image (i.e. the Autosave file from DSS) would be more useful. Once it is a jpeg, there's not much you can do with it. You will have to post it on a hosting site and link to it, because it will be too big for the forum.
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    Default Re: Taming bright stars

    Which hosting site do you recommend?
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    Default Re: Taming bright stars

    I used to use photobucket until they hijacked everyone's images. I don't recommend them. I haven't picked an alternative yet.

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    Default Re: Taming bright stars

    Ive been using flickr. It could also be placed in dropbox or some such.

    ps; PB did not hijack the images rather they took them hostage and hold them for ransom /endrant
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    Default Re: Taming bright stars

    I use Dropbox for this.

    Also, which processing program are you using?

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    Default Re: Taming bright stars

    Quote Originally Posted by chartram View Post
    I use Dropbox for this.

    Also, which processing program are you using?

    Mike
    Im using DSS to stack and Photoshop for the rest
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