Casitas de Gila, Gila, New Mexico, April 8 - 9, 2022
Walton, Oregon, April 23, 2022

Reprocessed 2/6/2023

Original Version:

During my Spring trip to a dark sky site in New Mexico, M94 was a prime target for imaging.  I used my Celestron 9.25” SCT at prime focus (FL = 2350mm, f/10). M94 was the first target of the night, and I captured about 6 hours of data nightly using Luminance, Red, Green, and Blue filters.  Two nights in New Mexico did not allow for enough good data to be acquired, so I imaged for one of the very few clear April nights in Western Oregon in to add some RGB and much more Luminance data.   I imaged the RGB data with 4 minute exposures and the Luminance with 2 minute exposures to prevent blowing out the core.  One goal for me was to capture the faint outer ring of stars, gas and dust.  The resulting combined image is adequate, but not completely satisfying.  While seeing and transparency were good in New Mexico, the moon was approaching first quarter, so the sky background was brighter and faint details were a bit washed out.  In Oregon, conditions started out with good seeing and transparency, but degraded as the night progressed.

Reprocessed (2023):

I continued my effort to reprocess most of the image data sets that had serious flaws and issues using new PixInsight tools and an improved workflow.  Again, Russ Croman’s XTerminator tools made a significant difference in improving the imaging and simplifying the workflow.  There were two challenges with this galaxy: 1) stretching was difficult as the luminance and RGB color images had a bright core and red disk, and a faint outer ring.  Successive applications of the GeneralizedHyperbolicStretch and CurvesTransformation tools were used.  2) Acceptable colors and saturation of the core and reddish disk were developed with successive applications of color masks and the CurvesTransformation tool.

Description:

M94, the Croc’s Eye Galaxy, is a spiral galaxy type SABa located in the constellation Canes Venatici.  It was discovered by Pierre Mechain in 1781 and it was observed and cataloged by Charles Messier later that year.  This galaxy has very interesting features.  It has a very bright core surrounded by tight spiral arms glowing with hot, blue stars.  The core and inner arms are surrounded by a large disk of stars, gas and dust that has very few star forming regions.  The reddish features hint at the extension of the spiral structures.  Outside of the bright ring is a 15’ diameter faint ring of stars, gas and dust.  These structures hint at gravitational “waves” with high and low mass densities.  The cause is not yet determined.  Furthermore, it is estimated that M94 has very little dark matter as measured by the rotation rate of the stars.  This too is a puzzling finding in that there is no explanation for how the galaxy formed and evolved without a dark matter halo.  M94 is about 14 Mly from Earth with a diameter of about 32 kly. (Wikipedia, NASA and SkySafari Pro).

Imaging details:

Celestron 9.25" Edge HD SCT (FL = 2350mm, f/10)
Celestron 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)
ZWO 36mm Luminance, Red, Green, and Blue filters
Equatorial camera rotation: 340 deg

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 XTerminator tools, etc.
    Photoshop CC 2022/2023

Luminance    2 min x 155 subframes (310 min), Gain 100, Offset 68, 1x1 binning
Red        4 min x 33 subframes (132 min), Gain 100, Offset 68, 1x1 binning
Green    4 min x 30 subframes (120 min), Gain 100, Offset 68, 1x1 binning
Blue       4 min x 29 subframes (116 min), Gain 100, Offset 68, 1x1 binning

Total integration time: 11.3 hours