Celestial hemisphere:  Southern  ·  Constellation: Dorado (Dor)  ·  Contains:  IC 2115  ·  IC 2116  ·  NGC 1760  ·  NGC 1761  ·  NGC 1763  ·  NGC 1769  ·  NGC 1773  ·  NGC 1776

Image of the day 01/23/2025

    NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield
      NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield

      NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars

      Image of the day 01/23/2025

        NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield
          NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield

          NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars

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          Description

          NGC 1763 itself is the blue, bean shaped object near the center.  Just below that, in a dark area inside the emission nebula, is NGC 1761.  This is a small open cluster of about 50 massive young blue stars.  These are among the largest known stars in the Universe and have carved out the central dark area here.  The overall structure of 1763, 1761, and nebulae 1760, 1769 and 1773, are said to resemble the Rosette.  I can confirm how hot and blue those stars are as I had to mask in a much less stretched version of them to prevent them from being completely blown out. 

          I tried a quite different method (for me at least) of combining the RGB and SHO data here.  I have been mostly adding continuum subtracted NB data to my RGB master lately.  Since I had strong data in all three NB channels I thought I might try creating a Foraxx palette of SHO and adding that to the RGB.  But I wanted to add only continuum subtracted SHO data, so I did the continuum subtraction first and  then created the Foraxx SHO from those.  The rough steps were:

          1) Create RGB Master
          2) Color Calibrate the RGB Master
          3) Continuum subtract the S, H, and O masters using the NightPhotons Script (I created a Blue-Green blend to subtract from the OIII)
               - I had the script produce starless masters
          4) Create a Foraxx SHO master from the Continuum subtracted NB masters
               - I did Linear fit the O and S to the H before creating the Foraxx SHO master
          5) Add the SHO master to the RGB in Pixelmath using [RGB+SHO-med(SHO)] in each of the three color channels  
          6) Run BlurX on the SHORGB master
          7) Run DeepSNR on the SHORGB master

          This produced the file I used for the Color data.  I wanted to use a PsuedoLuminance from the Narrowband masters (not continuum subtracted).  I also wanted to use DeepSNR on the data so I needed to use a slightly more complicated method for creating the PsuedoLuminance.  I started by creating a straight SHO master.  I ran DeepSNR on that master - it requires a three channel, RGB file to run.  I then extracted each of the three now denoised channels into separate files.  Those where next combined in Pixelmath to a single PsuedoLuminance.  I leaned just a little more on the H and O for the PsuedoLum, using {S*.3 + H*.35 + O*.35]

          From there the processing was pretty typical.  I created a copy of the RGB master with a light stretch for the stars only data.  This star reduction helps us see more of the nebula in this dense starfield.  I really like the starless version too though so I included it in the mouse-over.

          Most of the remaining challenges surrounded HDR processing to limit the brightness of the OIII/Blue nebulae and brighten the dimmer and Ha/SII emission areas.

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            NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield
            Original
            NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield
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          NGC 1763 | A Rosette Look-alike with Some of the Largest Known Stars, Kevin Morefield