Linslaw Point, Walton, OR and Baker, NV
May 15 and June 10-11, 2021
Reprocessed 01/29/23

I started this project in Oregon and finished imaging in Baker Nevada.  While I had great anticipation for capturing the Needle Galaxy, the results were disappointing.  The final image lacked good sharpness, and the bright core was dull and diffuse.  There was at least one culprit leading to the failure: unrelenting wind in Oregon and Nevada.  I kept about 60% of the data.

The first processing attempt was done in 2021.  Since the clouds of Western Oregon have prevented any progress on current targets, I decided to process NGC 4565 from scratch.  With a little more experience and powerful new tools in PixInsight, I used my current workflow to create a much-improved version 2 of the Needle Galaxy.  The raw Fits images had issues with subpar tracking and guiding with my old Celestron CGEM mount and optical distortions around bright stars with the ZWO ASI 1600MM Pro camera.  After digging out my calibrated dark and flat masters for this target, I used the latest Weighted Batch Preprocessing (WBPP) script to create new integrated masters for the Luminance, Red, Green and Blue channels.  After running the DynamicBackgroundExtraction (DBE) tool on each channel, I used the SpectrophometricColorCalibration (SPCC) to calibrate a RGB combined color image.  SPCC had difficulty finding enough stars to create an effective model to adjust the colors of the stars properly.   However, the colors of the galaxy were spot on.  The stars were bloated and had significant chromatic aberration.  BackgroundNeutralization was then used on the RGB image.  Russ Corman’s BlurXTerminator salvaged the image as the deconvolution recovered much of a more “ideal” input image.  While most of the large and medium sized stars were corrected, color fringes remained, and the smallest star shapes and colors were not corrected sufficiently.  On the other hand, BlurX did a great job of restoring details in the galaxy.  BlurXTerminator was run on the RGB and Luminance images with the same star PSF calculated from the luminance channel with the FWHMandEccentricity script.  NoiseXTerminator was used on the RGB and luminance images with somewhat aggressive settings (80% denoise, 30% sharpen).  I spent more time learning how to use the GeneralizedHyperbolicStretch tool using an approach described on the Entering into Space YouTube channel.  Here, successive stretches used a symmetry point starting from the background and progressing to brighter regions of the galaxy to control and preserve the background and moving to the midtones.  Both RGB and luminance images were stretched using this technique.  StarXTerminator was used to create starless and stars images for both RGB and luminance channels.  After some fine tuning with various tools, the RGB galaxy image was blurred with the Convolution tool.  The luminance image was sharpened with the UnsharpMask tool and then contrast was enhanced with the HistogramEqualization tool run with three kernel sizes to bring out more detail at large, medium and small scales.  The luminance and RGB galaxy images were combined and saturated.  The RGB stars image was lightly processed, and minimal saturation was applied to limit the chromic aberrations and other distortions.  The luminance and RGB stars were combined.  The starless and stars images were combined with PixelMath to produce the near final image.  Photoshop was used to desaturate the distortions around the stars and to selectively sharpen and saturate galaxy features.  So, the galaxy looks decent while the stars remain problematic.  A key takeaway is that BlurXTerminator, NoiseXTerminator and StarXTerminator are game changers that can recover fine details hidden in the image data and improve the size and shapes of stars that were distorted by the optics, imaging system and atmospheric conditions.  Furthermore, the processing workflow is simplified 

NGC 4565, the Needle Galaxy, is an edge-on spiral of Type SA located in the constellation Coma Berenices.  The Needle Galaxy is a popular deep sky object for astrophotographers.  It is a galaxy that Charles Messier and contributors to his catalog should have found but missed.  William Herschel discovered it in 1785.  NGC 4565 is a large galaxy, about 192 kly in diameter.  It has a bright core and a pronounced central bulge.  The galaxy is about 39 Mly away (SkySafari Pro 6).

Imaging details:

Celestron 9.25" Edge HD SCT
Celestron 0.7x Focal Reducer (FL = 1645mm, f/7)
Celestron off-axis guider with a ZWO ASI 174MM mini guide camera
Celestron CGEM II mount
ZWO ASI 1600MM Pro cooled monochrome camera (-15C)
ZWO 36mm Luminance, Red, Green and Blue filters

Software: Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Celestron CPWI mount control, 
    SharpCap Pro polar alignment,
    PixInsight and Photoshop CC 2023

Luminance    2 min x 97 subframes (194 min), Gain 139, Offset 21, 1x1 binning
Red                4 min x 27 subframes (104 min), Gain 139, Offset 21, 1x1 binning
Green            4 min x 24 subframes (96 min), Gain 139, Offset 21, 1x1 binning
Blue               4 min x 30 subframes (120 min), Gain 139, Offset 21, 1x1 binning