Galaxy Season 20201 continues! This is the second image that resulted from data captured during the 4 days of nice weather this past weekend.

It is also the second time that I have shot these first two galaxies. The first time was last year in June. At that time I used the ASI294MC-Pro One Shot Color Camera on the William Optics 132mm FLT APO Refractor (My first imaging rig). I had 50 subs @ 180 seconds each. This time I shot with a mono camera - the ASI1600MM-Pro with the Astro-Physics 130mm F/8.3 APO refractor (My second camera rig). This time I shot with the L,R,G,&B filters, and then I added some capture with my Ha Narrow Band filter. I ended up with almost 7.5 hours of useful capture across the various filters, but I also shot with a quarter moon brightening the skies - so I have that working against me this time.

So first, a bit about these Galaxies…. I am literally copying what I wrote for my first capture attempt last year - just so you don't have to go looking for it….

These two galaxies are found in the constellation Canes Venatici.

NGC 4631 is the larger and brighter of the two. Located about 30 Million Light years from Earth, this galaxy has a wedge shaped form that resembles a whale, thus its name. NGC 4631 has a nearby dwarf elliptical galaxy, NGC 4627, as a companion. This is rare example of a double galaxy and as such, is listed in the Atlas of Peculiar Galaxies.

NGC 4656 , the Hockey Stick - also known as the Crowbar Galaxy, is a highly warped barred spiral galaxy. It's distinctive shape is due to a *recent* gravitational interaction with NGC 4631. The "hook" of the galaxy is also listed as it's own object, NGC 4657. Beyond the hook is a fuzzy patch which maybe a dwarf elliptical galaxy that is merging with NGC 4656.

Now a few words about the capture and processing here. I love the results and control you can have with a mono camera, but it can result in a lot of data! I captured photons over 3 evening and the capture alone, along with calibration frames came to 19.1GB of data. I then used the Pixinsight WBPP 2.0 script to calibrate and register the data and Image Integration to create the image masters. These processes created 6and additional 64 GB of interim data files. All of this boiling down to the jpeg you see here!

The LRGB captures were done with 120 second exposures and the narrowband Ha data was captured with 5 minute exposures.

During image processing I created a LRGB image in the normal way, but then I extracted the Red channel and blended it with the Ha channel and folded it back into the image. The goal here was to make the bright and excited Hydrogen-Alpha regions "pop" in the image - capturing detail that you just don't get with the Red filter alone.

I was fairly happy with the final result, but capturing this during a period with the moon out clearly costs me some of the subtle nebulosity in the region - I worked hard to bring this out in the processing but there is only so much you can do. In Rochester, NY - you learn to take advantage of the clear nights when you get them!

I also wished I had more Ha integration time - The Ha had a lot more noise that the other channels and that complicated the processing…..

Thanks for looking!

Pat

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Image Details:

*Number of frames is after bad or questionable frames were culled.

45 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II R Filter

31 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II G Filter

38 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II B Filter

62 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II L Filter

62 x 120 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II L Filter

16 x 300 seconds, bin 1x1 @ -15C, unity gain, Astronomiks 6nm Ha Filter

Total of 7.2 hours

30 Dark exposures

30 Dark exposures

30 R Flat Darks

30 G Flat Darks

30 B Flat Darks

30 L Flat Darks

30 Ha Flat Darks

30 R Flats

30 G Flats

30 B Flats

30 L Flats

30 Ha Flats

Capture Hardware:

Scope: Astrophysics 130mm Starfire F/8.35 APO refractor

Guide Scope: Televue 76mm Doublet

Camera: ZWO ASI1600mm-pro with ZWO Filter wheel with ZWO LRGB filter set,

and Astronomiks 6nm Narrowband filter set

Guide Camera: ZWO ASI290Mini

Focus Motor: Pegasus Astro Focus Cube 2

Camera Rotator: Pegasus Astro Falcon

Mount: Ioptron CEM60

Polar Alignment: Polemaster camera

Software:

Capture Software: PHD2 Guider, Sequence Generator Pro controller

Image Processing: Pixinsight, Photoshop - assisted by Coffee, extensive processing indecision and second guessing, editor regret and much swearing…..