Casitas de Gila, Gila, NM, October 3 - 5, 2023

LBN 576 (or SNR G116.9+00.1, Abell 85 and CTB 1) is a faint supernova remnant lying almost 10,000 light years from Earth.  It is also estimated to be about 10,000 years old.  Until recently it was thought to be a planetary nebula, but recent studies confirm it to be a supernova remnant, the closest one known to Earth.  This object, also called the Popped Balloon or Medulla nebula, is the remains of the ejecta created in a supernova explosion.  An expanding shock wave of material is interacting with a large gas cloud, causing light to be emitted in specific wavelengths from different elements, like hydrogen, oxygen, and sulfur.  The image also includes a large emission nebula consisting of several massive clouds of gas and dust.

Conditions were excellent over several nights at a dark sky site in New Mexico to image a supernova remnant and large emission nebula in the constellation Cassiopeia.  Seeing was average to above average and transparency was mostly above average to excellent.  One night did have some clouds that may have contributed to star halos in the RGB filter data.  Master frames were created with the Weighted Batch PreProcessing (WBPP) script in PixInsight.  The RGB filter data were used to create a stars only image and the RGB color image was calibrated with the SpectroPhotometricColorCalibration (SPCC) tool in PixInsight.  The real challenge was in combining Ha, OIII and SII master frames into a color image.  The supernova remnant in SI was similar to that in the Ha image, so I ended up creating a classing SHO Hubble pallet image.  I would have preferred to make something more colorful, but I was too lazy.  A starless nebula was created and combined with the RGB stars image to produce the first version.  Photoshop was used to fix some defects and enhance regions of the nebula with saturation, brightness, and sharpness.  The stars processing was subpar as the larger stars are not quite right and there are too many stars in the combined image.  Further refinement is needed to reprocess the stars and remove the smallest stars so that the nebula stands out.

Note that I also tested a new beta version of GraXpert, a gradient removal application that now has an AI based method that worked amazingly well on the RGB image.

Imaging details:

Stellarvue SVX102T refractor with 0.74x focal reducer (FL = 528mm, f/5.2)
ZWO large off-axis guider with a ZWO ASI 174MM mini guide camera
Losmandy G11 mount with Gemini 2
ZWO ASI 2600MM Pro cooled monochrome camera (-5C)
Chroma 36mm Hydrogen-alpha, Oxygen-III, Sulfur II, Red, Green, and Blue filters
Equatorial camera rotation: 0 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 a Polemaster camera,
    PixInsight 1.8.9-2,
    Photoshop 2023

Hydrogen-a 10 min x 32 subframes (320 min), Gain 100, Offset 32, 1x1 binning
Oxygen-III  10 min x 34 subframes (340 min), Gain 100, Offset 32, 1x1 binning
Sulfur-II      10 min x 33 subframes (330 min), Gain 100, Offset 32, 1x1 binning
Red             2 min x 33 subframes (66 min), Gain 100, Offset 32, 1x1 binning
Green          2 min x 25 subframes (50 min), Gain 100, Offset 32, 1x1 binning
Blue            2 min x 29 subframes (58 min), Gain 100, Offset 32, 1x1 binning

Total integration time: 19.4 hours