Trifid Nebula and Open Cluster M21 in Sagittarius
with 10" f/3.9 Astrograph
Uploaded 6/26/23

 
This
            is a composition that includes the Trifid Nebula M20, and the
            open cluster M21 to its lower right. Great care was taken to
            preserve correct colors of neblula and stars, and a special technique
            described below to bring up the extremely faint background hydrogen
            nebulosity. A total of 6.5 hours of data was taken over this
            month, with the following special processing steps: First, 90
            minutes of RGB data with the amazing Astronomik RGB filters was
            taken. On another night, an extra 2h of blue data to add to the
            B channel to reduce noise in the blue parts surrounding the pink
            core. As you know, the "Golden Standard" for a trifid
            shot is to see the blue wrap all the way around the pink part.
            We wanted to see what more could be captured. Second because
            nearly every amateur shot ever taken of this object shows brown
            or deep yellow stars due to interstellar dust, we corrected the
            color balance of every star in this image to a G2V balance thus
            we can match the color in this image to spectral type and see
            the full balance from gold to blues. Third, to bring up the invisible
            hydrogen in the background which is always lost in the star clouds,
            we used the same mathematical technique used by Bray Falls in
            which he discovered the huge OIII arc next to the galaxy M31
            recently that made all the news. Here we use a math equation
            to subtract the luminance from the unresolved star clouds from
            the Halpha data and bring out the invisible filaments and wreaths
            of structured hydrogen nebulosity. This then is combined with
            the RGB image. The results as you see here reveals an astounding
            amount of hydrogen in the field.

            
Select an image size for a larger view:

1600 x 1290


Instrument:  10" f/3.9 Orion Astrograph Newtonian with Baader MPCC
Mount:  Astrophysics 1200 QMD
CCD Camera:  ATIK 16200 
Guider: ASI120  w/80mm WO Zenithstar 81 piggyback refractor
Exposure:  6.5 hours HaRGB
Astronomik  RGB Combine Ratio:  1: 1.05: 1.5
Location:  Payson, Arizona, Elevation:  5150 ft.
Sky:  Seeing FWHM = 3 arcsec , Transparency 9/10
Outside Temperature:  5 F
CCD Temperature:  -30 C
Image Processing Tools: 
Maxim DL6:  Calibration, PixInsight:  All Remaining processing, Production finishing: Photoshop CS2

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