Gold Canyon, AZ, December 23, 2022

Since adding a 4” refractor to my telescope collection, I started to image open star clusters.  Photographing open clusters with a 9.25” SCT never produced acceptable results.  I imaged M44 as the last target of three for the night.  I collected data for red, green and blue filters, with 30 second exposures.  With f/5.2 optics, the brightest stars in were still slightly clipped (saturated).  Less than 1 hour was collected for each filter, so this was a test of how few subframes could be acquired and still produce a decent image.

I processed the data using a similar workflow in PixInsight as with other star clusters.  I have grown to love the WeightedBatchPreprocessing script to calibrate and integrate the R, G and B channels.  This time, I gave the new BlurXTerminator tool (from Russ Croman) a try to affect the stars.  BlurXTerminator uses a neural network to perform deconvolution, an inverse filtering method used to recover the original, more idealized input data from the actual images treated as the output of some transformation function.  The results are fantastic, with BlurXTerminator shrinking stars, correcting PSFs, and reducing larger halos.  However, there are some residual halos and chromatic fringes in the bright stars.  This tool is a game changer as described on many YouTube astrophotography channels and websites.  While a bit pricy, it is worth the cost of admission.  So, image processing with three AI-based tools, BlurXTerminator, NoiseXTerminator and StarXTerminator, has been greatly simplified and the resulting images are superior to those processed with other more traditional tools in PixInsight.  With limited integration time, the RGB image had significant  background noise.  NoiseXTerminator with aggressive settings was applied in the linear state.  After stretching, the MultiscaleLinearTransform tool was used to reduce chrominance noise.

The Beehive Cluster, also known as Praesepe (Latin for "manger" or "crib"), is an open cluster in the constellation Cancer. One of the nearest open clusters to Earth, M44 contains a larger population of stars than other nearby bright open clusters holding around 1,000 stars.  Under dark skies, the Beehive Cluster looks like a small nebulous object to the naked eye and has been known since ancient times.  Classical astronomer Ptolemy described it as a "nebulous mass in the breast of Cancer".  It was among the first objects that Galileo studied with his telescope.  Age and proper motion coincide with those of the Hyades, suggesting they may share similar origins.  Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with many main sequence stars.  The distance to M44 is between 520 and 610 light years.  The cluster has an age of about 600 million years, compared to about 625 million years for the Hyades.  The diameter of the bright inner cluster core is about 23 light years. (Wikipedia)


Imaging details:

Stellarvue SVX102T with SFR0.74 focal reducer (FL = 528mm, f/5.2)
ZWO off-axis guider (OAG-L) with a ZWO ASI 174MM mini guide camera
Losmandy G11 mount with Gemini 2
ZWO ASI 2600MM Pro cooled monochrome camera (-10C)
Chroma 36mm filters:  Luminance, Red, Green, and Blue
Equatorial camera rotation: 270 degrees

Software:    Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Losmandy Gemini ASCOM mount control and web client interface,
    SharpCap Pro for polar alignment with the Polemaster camera,
    PixInsight 1.8.9-1 with BlurXTerminator, StarXTerminator, NoiseXTerminator,
    Photoshop CC 2022

Red       30 sec x 72 subframes (36 min), Gain 100, Offset 68, 1x1 binning
Green    30 sec x 64 subframes (32 min), Gain 100, Offset 68, 1x1 binning
Blue      30 sec x 64 subframes (32 min), Gain 100, Offset 68, 1x1 binning

Total integration time: 1.7 hours.