Baker, NV and Linslaw Point, Walton, OR
June 10-11 and July 4, 2021

Reprocessed 2/3/2023

This project was done during a mount upgrade from my Celestron CGEM II to a Losmandy G11 system.  I started to image NGC 6946, the Fireworks Galaxy, over two nights in Baker Nevada.  After fighting the wind with the Needle Galaxy as the first target, NGC 6946 was high in the sky as the second target for each night.  The wind did subside late, and the seeing and transparency were above average.  In July, I captured more subframes in Walton, Oregon.  This included an insufficient amount of hydrogen- narrowband data.  I also came up short on Luminance data, something to be rectified in future outings.  I combined Ha and Lum as well as Ha and Red using the new Combine function in PixInsight’s PixelMath tool.  The Oregon imaging session was the first test of my new Losmandy G11 mount and a QHY Polemaster camera.  I used SharpCap Pro’s polar alignment tool with the Polemaster.  SharpCap’s polar alignment tool is very easy to use, and I obtained an alignment in about five minutes with an error of less than 3 arc minutes as measured by PHD2’s Guiding Assistant.  The Losmandy G11 mount performed very well with a PHD2 guiding RMS (standard deviation) between 0.4 and 0.6.  Again, seeing and transparency were good and the G11 was more tolerant of light wind than the CGEM II.

Reprocessing 2/3/2023:

The original galaxy image lacked details, the stars were bloated, and the color was too red (from the addition of the Hydrogen-alpha data to the red channel).  The other issue was that I did not acquire nearly enough luminance subframes to have a high signal to noise ratio.  I compensated by combine luminance with Ha data.  As with other reprocessed galaxies, I employed my current workflow in PixInsight and relied on the WBPP script, SPCC color calibration, and Russ Croman’s XTerminator tools to generate a much-improved result.  Note also that these tools really do reduce the image processing time.  I reprocessed the Ha + Luminance combination to enhance the emission regions and then deemphasized the stars.

Description:

NGC 6946 is a spiral galaxy of type SAB.  It is located on the border between the constellations Cygnus and Cepheus.  Its arms have prolific star forming regions with many emission nebulae.  It is not understood why this galaxy is so active.  However, there may have been a recent accretion of a rich gas cloud providing fuel for the fireworks.  The Fireworks Galaxy is also photogenic because sits behind a rich Milky Way star field in Cygnus.  NGC 6946 may be a remote member of our Local group of galaxies.  The galaxy is between 22 and 29 Mly from Earth, and it is almost 73 kly in diameter (Stellarium and SkySafari Pro 6).

Imaging details:

Celestron 9.25" Edge HD SCT
Celestron 0.7x Focal Reducer (FL = 1645mm, f/7)
Celestron off-axis guider with a ZWO ASI 174MM mini guide camera
Celestron CGEM II mount and Losmandy G11 mount
ZWO ASI 1600MM Pro cooled monochrome camera (-15C)
ZWO 36mm Luminance, Red, Green and Blue filters

Software:    Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Celestron CPWI mount control and Losmandy Gemini ASCOM mount control,
    SharpCap Pro polar alignment,
    PixInsight and Photoshop CC 2021/2023

Luminance    2 min x 37 subframes (74 min), Gain 139, Offset 21, 1x1 binning
Red        4 min x 34 subframes (136 min), Gain 139, Offset 21, 1x1 binning
Green    4 min x 34 subframes (136 min), Gain 139, Offset 21, 1x1 binning
Blue      4 min x 35 subframes (140 min), Gain 139, Offset 21, 1x1 binning
Hydrogen-a    10 min x 9 subframes (90 min), Gain 139, Offset 21, 1x1 binning