Whale Galaxy NGC4631

Discussion in 'My Astrophotos' started by ROBERT T SCHAEFER JR, Apr 18, 2019.

  1. ROBERT T SCHAEFER JR

    ROBERT T SCHAEFER JR Cyanogen Customer

    Joined:
    May 13, 2018
    Messages:
    213
    CanonEOSII RebelT7i 'mod. UV-IR @ Hutech' thru a TPO80A filter thru a TeleVue 2.5XPowerMate for
    3000mmF/l on an Astro-Physics 1200GTO '2010' Mount for four CR2.s at 668secISO6400 and
    'calibrated' in MaximDL Pro V6.16 and Average stacked . Then the 16BIT FITS was put into
    "ImagesPlus" for more commands .x

    {This image is four CR2.s Average stacked which I read in an old CCDOps webpage that to
    'average' four images together 'doubles' the SNR … is this better than Sum stacking which
    might just make the stacked image thicker with the same SNR as a single image ?}
     
  2. Doug

    Doug Staff Member

    Joined:
    Sep 25, 2014
    Messages:
    6,892
    No, there is absolutely no difference whatsoever between these two things, except for a scaling factor.

    Average = (A + B + C + D) / 4.

    Sum = A + B + C + D.

    Therefore Sum = Average * 4.

    Obviously taking an image and simply multiplying every pixel by a constant does not change the signal-to-noise ratio. It increases the signal by 4 and increases the noise by 4.

    Average has exactly the same effect on SNR as Sum.
     

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