M106 or NGC4258 is an intermediate spiral galaxy in the constellation Canes Venatici. Its peculiarity is the presence of nuclear water “masers” of galactic scale that provide the distinct purple arm colors.

This is also a very special image as it is the last target I shot with the ASI1600MM before I retired the camera for the new APS-C ASI2600MM. Farewell loyal 1600!

I could only grab a limited amount of exposures in December 2020 before winter hit with two months of constant rain and snow storms. By the time skies cleared up I was doing some maintenance at the observatory and swapped cameras, so I decided to process the available dataset. Total integration time 7.5hrs in LRGB (3hrs L, 1.5hrs RGB each).

Full resolution here

Processing details


LRGB calibration, weighting, alignment, integration (drizzle integration vark 1.5), crop, Integer downsample 2x


  • Crop
  • DynamicBackgroundExtraction
  • EzDecon with GAME mask on M106
  • Integer downsample x2
  • EzDenoise,
  • HT stretch
  • Duplicate + hdr to enhance details in the galaxy core
  • Blend hdr version back into L with mask to only select M106
  • LHE with GAME mask on M106
  • EzStarReduction MorphTransf order 2


  • Crop
  • DynamicBackgroundExtraction
  • Integer downsample x2
  • LinearFit of R and B masters to G master
  • Channel combination
  • Background Neutralization
  • Color Calibration
  • HT + ArchSin for stretching
  • LRGB combination with L master


  • Enhanced saturation and contrast with luminosity masks
  • Non linear noise reduction protecting stars
  • various curves, contrast and color adjustments with masks

Caprile Observatory

Caprile Astronomical Observatory, Astrophotography, located in Tuscany (Italy) countryside. A photographic journey across the marvels of the universe | Galaxy | Nebulae | Deep Sky Objects