Rosette Nebula (C49) - A Deep Space Rose in Narrowband

The Rosette Nebula (Caldwell 49) is an H_II region located in the constellation Monoceros. With a diameter of approximately 130 light-years, it's a prominent emission nebula situated about 5,000 light-years from Earth.

This image was captured using narrowband filters (H_α, O_III, and S_II), which effectively isolate specific wavelengths of light emitted by ionized gases. This technique allows for detailed imaging even from light-polluted urban locations (Bortle 8 in this case).

Technical Information

The Rosette Nebula contains several distinct regions of interest:

• The central open star cluster NGC 2244, whose hot, young stars provide the energy that ionizes the surrounding hydrogen gas
• A large, roughly circular emission region with complex filamentary structures
• A central void created by stellar winds from the cluster's massive stars

The data was collected on January 11, 2025, using a ZWO ASI2600MM Pro camera and William Optics Redcat 51 telescope. The acquisition consisted of 8 × 300s exposures in H_α, 7 × 300s in O_III, and 4 × 300s in S_II, all using Antlia 3nm narrowband filters. This represents a total integration time of approximately 1.6 hours (19 × 5 minutes). The HOO palette with S_II screening was used to create a false-color representation that highlights the nebula's structure.

Processing details

The narrowband data was processed using PixInsight, with the following steps:

• WBPP (PSF Scale SNR, LocalNormalization, Drizzle 1x)
• Background Extraction using GradientCorrection
• Deconvolution using BlurXTerminator
• Stars Removal using StarXTerminator
• HOO combination and Narrowband Normalization
• Stretching using Statistical Stretch and GHS
• S_II: star removal and stretch
• Screening S_II into HOO image using ImageBlend and colorization option
• Noise reduction using NoiseXTerminator
• Blending stars using ImageBlend
• Adjusting Black point and Color saturation