Celestial hemisphere:  Southern  ·  Constellation: Virgo (Vir)  ·  Contains:  M 104  ·  NGC 4594  ·  Sombrero Galaxy
M104 - Sombrero Galaxy, Pleiotrope
M104 - Sombrero Galaxy
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M104 - Sombrero Galaxy

M104 - Sombrero Galaxy, Pleiotrope
M104 - Sombrero Galaxy
Powered byPixInsight

M104 - Sombrero Galaxy

Equipment

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Acquisition details

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Description

I've always loved this galaxy but haven't been able to capture it until I made it out to a proper dark site. I'm happy with how this came out despite it being a small target for my 4" refractor.

I faced a couple challenges with this acquisition, notably:
  1. I am fairly sure the 0.8X field flattener/reducer created oblong/pear-shaped stars in the image. These weren't due to tracking errors (they appear regardless of exposure), and images without the reducer don't show the same issues. I'm not sure if this is due to the way the flattener attaches to the AT102ED focuser- maybe it's tilted?
  2. While the AT102ED doesn't have a ton of chromatic aberration visually, in imaging it manifests as very bloated blue stars. I've tried using more restrictive UV/IR filters which partially mitigate the star bloat, but so far the only thing that really helps is the Optolong L-Pro filter, and even then it's still very noticeable. I don't know if my scope is unusually bad with this or it's just par for the course for an inexpensive doublet.
  3. Amp glow from the ASI183MC Pro: this one caught me by surprise since I normally image with an astroberry, but the amp glow is qualitatively different between images captured when the camera is connected to 1) the USB3 ports of the astroberry, 2) the USB2 ports of the ASIair mini, and 3) the USB3 ports of my laptop. Using darks captured using different connections/computers won't necessarily calibrate out.
  4. The ASIAir software saves incorrect astrometric solutions to the FITS header, which interferes with downstream processing.

PixInsight processing details:
  • Calibration, cosmetic correction, local normalization and CFA drizzle integration (2x, 0.9 drop shrink). Note: CFA drizzle does a TON to help reduce the mottled chromatic noise characteristic of OSC cameras. I'm going to prioritize dithering whenever possible when using OSC cameras going forward.
  • Spectrophotometric color calibration (after manually specifying the initial image location)
  • Deconvolution using BlurXTerminator (no stellar sharpening, only correction and DSO sharpening performed due to artifacts introduced by odd star shapes)
  • Integer resampled to half-size (i.e. the native resolution of the sensor)
  • Separated stars using StarXTerminator
    • Starless image:
      • RGB stretched using masked stretch and denoised using NoiseXTerminator
      • Synthetic luminance stretched using generalized hyperbolic stretch (GHS)
      • LRGB recombination

    • Star image:
      • Stretched using GHS with aim of minimizing star halos

  • Stars + starless recombined using re-screening
  • Stars reduced using Bill Blanshan's excellent Pixelmath star reduction scripts (here)

Comments

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M104 - Sombrero Galaxy, Pleiotrope