Target: Rosette Nebula (C49)
Date: December 14, 2025
Location: My Backyard in Georgetown, Texas
Conditions: Clear skies, 28°F, light winds, Moon: Waning Crescent/25% illuminated.
Bortle Class: 5
The Rosette Nebula (also known as Caldwell 49) is an H II region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The cluster and nebula lie at a distance of 5,000 light-years from Earth and measure roughly 130 light years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. The mass of the nebula is estimated to be around 10,000 solar masses.
Like so many others, the Rosette Nebula is one of my perennial favorite targets in the night sky. This was my first time using my Dwarf 3 to image it, and I was not disappointed. I was able to gather so much data with only 4 hours of integration using 30-second subs. I limited the subs to 30 seconds as this seems like the sweet spot of the amount of light pollution in my area. The dual-band filter really helped with this and allowed me to use a narrowband normalization workflow.
I’d like to get some more time on the Rosette once we get some clear skies.
Equipment Used
Telescope: Dwarf 3
Filters: Dual-Band
Post-Processing Workflow
Stacking in Siril and exported for processing in PixInsight
Dynamic Crop
Spectrophotometric Color Calibration / Flux Calibration
Multiscale Gradient Correction
BlurXTerminator: Default settings
NoiseXTerminator: Default settings
StarXTernimator
GraXpert on starless image
Generalized Hyperbolic Stretch on starless image
Extracted RGB Components: Deleted blue channel and recreated in Pixel Math using R*.6+G*.4
Created false color palette using LRGB Combination: Luminance = R, Red = R, Blue = G, Green = G
Used blue and yellow mask to adjust color saturation using curves adjustment tool
Applied Seti Astro star stretch to star image.
Combined starless image with the stars by rescreening them in Pixel Math using ~(~SL*~S).
Exported as PNG.
