Casitas de Gila, Gila, NM, October 12 - 14, 2023

NGC 6888 is an interesting emission nebula in the constellation Cygnus.  The bright star in the center, V1770 Cyg, is a very large, hot, blue-white star.  The star became a red giant about 400,000 years ago and it shed its outer layer as a solar wind.  The hot blue-white star now sheds about a solar mass every 10,000 years at high velocity. The glowing shell is the result of the heating from the fast moving, high energy solar wind colliding with the slower moving shock waves from the red giant phase.  This creates the enormous crescent shape of glowing ionized gas.  Within 1 million years, the blue-white star will go supernova.  NGC 6888 has a diameter of about 31.6 light years, and it is approximately 4700 light years from Earth (SkySafari Pro).  The very faint planetary nebula near the center, PN G75-5+1-7, is known as the Soap Bubble.  Below it is the open star cluster, IC 4996, the P Cyg Cluster.

Processing to produce an HOO pallet image was very straight forward.  The only issue was that SPCC in PixInsight failed on the RGB image with the settings that have I used on all other images.  Perhaps the very dense star field confounded the star identification and spectral mapping.  I changed the limiting star brightness from Auto to magnitude 15 to make SPCC work.  The color calibration model fit was not very good, so the star colors may be slightly off.

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 (-10C)
Chroma 36mm Hydrogen-alpha, Luminance, 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 2024

Hydrogen-a  10 min x 25 subframes (250 min), Gain 100, Offset 32, 1x1 binning
Oxygen-III  10 min x 29 subframes (290 min), Gain 100, Offset 32, 1x1 binning
Red             2 min x 36 subframes (72 min), Gain 100, Offset 32, 1x1 binning
Green          2 min x 32 subframes (64 min), Gain 100, Offset 32, 1x1 binning
Blue            2 min x 32 subframes (64 min), Gain 100, Offset 32, 1x1 binning

Total integration time: 12.3 hours