Barnard 150 - The Seahorse Nebula: Image Processing Walkthrough

Written By Patrick A. Cosgrove

October 2, 2025

My Image of Barnard 150 - The Seahorse Nebula

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    Special Note

    Welcome to the New Image Processing Page for this project! You got here by following a link in the main Image Project Report, and you can easily return to that by using the back button on your browser.

    Abbreviations Used

    BXT BlurXerminator by RC-Astro

    CC Cosmetic Correction

    CT CurvesTransformation Process

    DBE Dynamic Background Extraction Process

    ET ExponentialTransformation

    HT HistogramTransformation

    NXT NoiseXerminator by EC-Astro

    SCNR Subtractive Chromatic Noise Reduction Process

    SPCC SpecttrometricColorCalibration

    STF Screen Transfer Function

    STF->HT Method - dragging the STF triangle to the base of the HistorgamTransformation tool and

    then applying this to the image to go nonlinear

    SXT StarXterminator by PC-Astro

    WBPP Weighted Batch Preprocessing Script

    Processing this Image

    (All Processing is done in Pixinsight, with some final touches done in Photoshop)

    1. Blink

    • General

      • Lots of satellite tracks - easy to handle

      • Evidence of a light pollution gradient towards the north

    • Lum

      • 13 frames removed for thin clouds

    • Red

      • 6 frames removed!

    • Green

      • 7 Frames removed for clouds.

    • Blue

      • 6 Frames removed for clouds.

    • Darks

      • All looks ok

    • Dark Flats

      • All looks ok

    • Flats

      • all good

    2. WBPP 2.8.9

    • Reset everything

    • Load all lights

    • Load all flats

    • Load all darks

    • Select - maximum quality

    • Reference Image - auto - the default

    • Select the output directory for the WBPP folder

    • Enable CC for all light frames

    • Pedestal value - auto

    • Darks -set exposure tolerance to 0

    • Lights - set exposure tolerance to 0

    • Lights - all set except for a linear defect

    • set for Autocrop

      WBPP run 2:42:08 - no errors

    WBPP Calibration View

    WBPP Post Calibration View

    WBPP Pipeline View

    3. Load Master Images and Create Color Images

    • Load all master images and rename them.

    • Using CombineChannels, create the Master RGB image

    Master L, R, G, and B images.

    Initial RGB Color Master Image.

    4. Initial Process of Linear RGB data

    • Run DBE for the RGB linear image. Use subtraction for the correction method. Choose a sampling plan that avoids the nebulae (see below)

    • Run BXT - correct only. This cleans up and stars at the corners. Not much to do in this image as the scope is very crisp.

    • Select a preview rectangle that samples the background sky, and then set up and run SPCC.

      • Use the 571 device curve

      • Use ZWO R, G, & B filter curves,

    • Run Full BXT - I am using default values here as I do not want to shrink the stars too much.

    • Run NXT V3 - see params from snapshot below

    • Run SXT and save the RGB stars.

    Master RGB Image DBE Sampling Plan (click to enlarge)

    MasterRGB- Before DBE (click to enlarge)

    Master RGB after DBE (click to enlarge)

    Background Subtracted by DBE (click to enlarge)

    SPCC Panel Settings

    SPCC Regression Results

    Master RGB image before SPCC (click to enlarge)

    Master RGB after SPCC (click to enlarge)

    Measuring Star Sizes with PFSImage Script (click to enlarge)

    BXT Settings Used. (click to enlarge)

    NXT Panel used. (click to enlarge)

    Master RGB Before BXT Correct Only, After BXT Correct Only, After SPCC, After BXT Full, After NXT

    Final Master RGB Image

    Master RGB Starless Image (click to enlarge)

    Master RGB Stars Image (click to enlarge)

    5. Process the Linear Lum Data

    • Run DBE for the Lum linear image. Use subtraction for the correction method. Choose a sampling plan that avoids the nebulae.

    • Run BXT - correct only. This cleans up and stars at the corners.

    • RUN PFSImage to get the star sizes. X = 2.49, Y= 2.59

    • Run Full BXT - I used values that were approximately 1/3 larger than the measured star size. I find this often works for me.

    • Run NXT V3 - refer to the parameters from the snapshot below.

    • Run SXT.

    Master L DBE sampling Plan (click to enlarge)

    Before DBE (click to enlarge)

    Master L after DBE (click to enlarge)

    Master L Background subtracted (click to enlarge)

    Measuring L star sizes.

    Params used for BXT

    NXT Params used.

    Master L before BXT Correct Only, After BXT Correct Only, After BXT Full, After NXT V3

    FInal Master L imge

    Master L Starless image after SXT.

    6. Go Nonlinear

    • Use Seti Astro Star Stretch Script to stretch Stars

    • Use STF->HT method to stretch the starless images.

    Star Stretch Script panel and params used.

    Nonlinear RGB Stars image

    Nonlinear Lum image (click to enlarge)

    Nonlinear RGB Starless image click to enlarge)

    Starrting L image (click to enlarge)

    7. Process the Lum Starless Image

    • Noise is a big issue. So I am starting with NXT to kill it at the start. See the params used.

    • Next is ExponentialTransform (ET) - this is to stretch the low levels of detail here. See screensnap for params used.

    • One more NXT is done, and that is all I am going to do. This brings out detail available in the Lum image without causing more noise or noise artifacts. I went really light on stretched here for the most part,

    NXT Params used.

    After NXT (click to enlarge)

     

    ET Params used on this image.

     

    After ExponentialTransformation (ET) (click to enlarge)

    FInal NXT for Lum image.

    After final NXT - The final Lum image.

    8. Process the Nonlinear RGB Image

    • Apply a modest CT boost for tonescale and color saturation. Treading softly to avoid ramping up noise

    • Next, ET is applied to boost low-level detail. See screensnap for params used.

    • CT to boost color and Tone.

    • Noise is popping up with that last change, so let’s do NXT again. See screensnap for params.

    • The image now is showing some magenta color biases after that last stretch. Best we fix this with the following sequence:

      • Invert (make magenta into green)

      • SCNR for Green at 1.0 (remove the green)

      • Invert the image again

    • Blend in the Lum image using the ChannelCombination tool in color mode and enable just the L channel - see panel screensnap below.

    • Do a CT to tweak the color and tones

    • I would like to adjust the background sky, so I will create a BlueMask

      • Use the ColourMask process to create an initial mask:

        • Hues from 158 to 148

        • Blur of 7.0

      • Use CT to boost the mast

    • Apply the mask and do a CT to darken and adjust the colors of these regions.

    • Do a final NXT run with the params shown in the screensnap

    • Apply Unsharp Mask to sharpen things slightly.

    Initial nonlinear RGB Starless image (click to enlarge)

     

    ET Params used.

     

    After CT to boost tone and color (click to enlarge)

    After NXT (click to enlarge)

    Apply SCNR with Green at 1.0 (click to enlarge)

     
     

    CT to adjust Tone (click to enlarge)

    Initial BlueMask (click to enlarge)

    After CT with the BlueMask (click to enlarge)

    After CT Boost (click to enlarge)

    After ET boost (click to en;arge)

    Anotehr Application of NXT - these are the params used.

    Invert Image (click to enlarge)

    After Invert (click to enlarge)

    Using the ColourMask Process to create a blue mask (click to enlarge)

    After CT Boost on the mask (click to enlarge)

    NXT Params used on the next step.

    After NXT

    Unsahrp Mask Params used.

    Final LRGB Starless image.

    9. Add The Stars Back In

    • Do a slight CT to boost color sat on the stars’ image

    • Use the ScreenStars Script to add the stars back in.

    Stars - after a slight color sat boost with CT (click to enlarge)

    Final LRGB starless image. (click to enlarge)

    ScreenStars App used to add the stars back in.

    Final image, ready for polishing

    10. Export the Image to Photoshop for Polishing

    • Save the image as a TIFF 16-bit unsigned and move to Photoshop

    • Make final global adjustments with Clarify, Curves, and the Color Mixer - slight tweaks really

    • Added Watermarks

    • Export Clear, Watermarked, and Web-sized jpegs.

    The Final Image!

    Patrick A. Cosgrove

    A retired technology geek leveraging his background and skills in Imaging Systems and Computers to pursue the challenging realm of Astrophotography. This has been a fascinating journey where Art and Technology confront the beauty and scale of a universe that boggles the mind…. It’s all about capturing ancient light - those whispering photons that have traveled long and far….

    https://cosgrovescosmos.com/