Casitas de Gila, Gila, NM, April 3 - 12, 2024

In April, I made my annual Spring trip to New Mexico for galaxy season; so many galaxies, so little time.

Description:

The Medusa Nebula is a planetary nebula in the constellation of Gemini.  It is also known as Abell 21 and Sharpless 2-274.  It was originally discovered in 1955 by University of California, Los Angeles astronomer George O. Abell, who classified it as an old planetary nebula.  With the computation of expansion velocities and the thermal character of the radio emission, Soviet astronomers in 1971 also concluded that it was most likely a planetary nebula. (Wikipedia)

Gemini and Sh2-174 were past the meridian when the nightly sessions started, so about two hours were available for imaging the first target while the galaxies scheduled rose higher.  Later, the waxing moon travelled too close to the nebula, preventing the capture of more Red, Green and Blue filter subframes for the stars.  I experimented with using 5 2-minute subframes to create RGB stars.  The result was just adequate.  Hydrogen-alpha and Oxygen-III narrowband filters were used to capture the emission nebula.  An HOO false color image was created.  The stars were removed, and the starless image was processed using PixInsight and Photoshop.  The RGB stars image was stretched and saturated, and chromatic aberrations were corrected in Photoshop.  The HOO starless and stars images were combined in PixInsight and finished in Photoshop.

Imaging details:

Celestron 9.25" Edge HD SCT with 0.7x Focal Reducer (FL = 1650mm at f/7)
Celestron Off-axis Guider with ZWO ASI 174 mini guide camera
Losmandy G11 mount with Gemini 2 controller
ZWO ASI 2600MM Pro cooled monochrome camera (-10C)
36mm Chroma filters: 5nm Hydrogen-alpha, 3nm Oxygen-III, Red, Green and Blue

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-alpha    10 min x 19 subframes (190 min), Gain 100, Offset 64, 1x1 binning
Oxygen-III              10 min x 22 subframes (220 min), Gain 100, Offset 64, 1x1 binning
Red                         2 min x 5 subframes (10 min), Gain 100, Offset 64, 1x1 binning
Green                     2 min x 5 subframes (10 min), Gain 100, Offset 64, 1x1 binning
Blue                        2 min x 5 subframes (10 min), Gain 100, Offset 64, 1x1 binning

Total integration time: 7.33 hours