The Rosette Nebula -- a stunning emission nebula associated with the star cluster NGC 2244 -- is a complex and challenging target, worthy of repeated efforts.
Appearing in the constellation Monoceros (the Unicorn, east of Orion), the nebula and cluster are estimated to be about 5,000 light years distant, spanning a diameter of about 130 light years.
For astro-imagers, capturing the detail of the swirling gas clouds and the numerous bok globules (dark nebulae composed of dust and gas found in many emission nebulae), while preserving the Rosette's glorious colors, usually requires combining multiple images shot through a variety of filters.
The Rosette covers a wide area of sky. Each of the below images was taken with the ASI1600 through the 72mm refractor.
The above image was my first try this season, taken in September. It comprises 12, 360-second exposures through the Ha filter and 10, 180-second exposures through the R, G and B filters.
This month, I returned to the Rosette, capturing just over two and a half hours (31, 300-second sub-exposures) through the Ha filter, producing the above image. Ha brings out an incredible amount of detail of the nebula's structure.
I then captured an hour and 15 minutes of 300-second sub-exposures through the OIII filter, combining them with the previous Ha data to create the above HOO palette image. This narrowband-only exposure keeps the general color of the nebula, while revealing a lot of subtle detail. Total exposure time is 3 hours and 45 minutes.
Last weekend, I captured 2.5 hours of RGB data (10, 300-second sub-exposures per channel), which I then combined with the existing 2.5 hours of Ha data, creating the above image. Total exposure time for this image is about five hours.
Time and weather permitting, the next step will be to obtain more OIII data and possible SII data, creating a better HOO palette image and a separate SHO palette image -- and then combining the SHO an RGB data for a final image for the season.
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