As I wait for more data under skies that continue to worsen as we get into late fall, to complete my projects, my need to process is (partly) satisfied by purchased data from Insight.
The GalaxyOften known as the Bubble Galaxy, because of the huge halo, NGC 3521 is a flocculent spiral about 35 million light-years from us. The spiral arms, and indeed much is the galaxy, is broken up into fluffy patches of stars and dust. Thus, the spiral character is somewhat ill-defined. There is a slight bar, a weak inner ring, and moderate to loosely wound arm structure, thus it is categorized as an intermediate spiral: SAB(rs)bc. The galaxy is about one-half the diameter on our Milky way, about 50,000 light years across and is inclined by 72.7° to our line of sight.
The core has an HII region and a low-ionization nuclear emission-line region (Liner). The spectra for a Liner core typically includes line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+ (ie. OI, OII, NII and SII), while emission from strongly ionized atoms, such as O++, Ne++, and He+ (OIII, NeIII and HeII) is relatively weak. The mechanism for the ionization is not clear, it maybe be there is an active galactic nucleus (AGN) with a supermassive black hole, or the emission is powered by star forming regions.
The Insight HaLRGB Data- Total Integration: 7 hrs 35 min
- Lum: 32x300 s = 2h 40 m
- RGB: 15x300 s = 1h 15m each
- Ha: 7x600 s = 1 h 10 m
The Insight setup is ATEO-1, which is:
- Dreamscope 16" f/3.7 Astrograph
- Software Bisque Paramount ME Mount
- FLI Proline 16803 Camera
- SkyPi Remote Observatory in Pie Town, New Mexico
My ProcessingI produced individual LRGB and Ha stacks using DeepSkyStacker. The Halpha data had been binned 2x so I used a 2X drizzle to match the LRGB data.
I composed the image in StarTools, cropping and binning slightly (bin =0.71), followed by wipe (background extraction), a digital development with some adjustments to gamma, HDR, deconvolution, Ha accents addition, initial color, star reduction and a superstructure isolation.
In Photoshop I separated the galaxies from the stars using StarXterminator, then did an APF-R multi-scale unsharp mask on the galaxies only. Stars were added back in with a linear dodge (add). Both layers were then adjusted for color, noise reduction using Astronomy Tools and NoiseXterminator.
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