Rosette nebula

The “Rosette nebula” is a H-II region (HII = ionized hydrogen) located close to a giant molecular cloud in constellation Monoceros. The open star cluster NGC 2244 (discovered in 1690 by John Flamsteed) in the centre is considered to be the origin of the ionizing radiation. The target lies at a distance of 5000 light-years and is roughly 130 light-years in diameter, with a mass of about 10.000 solar masses.

I obtained my first picture in 2018, using the Canon EOS 600D. Because it was a test image, the exposure was short, only about 35 minutes, see below.

Rosette Nebula (NGC 2244), 16 November 2018, Vorst, William Optics 110 mm APO FLT f/7, Canon EOS 600D, UV-IR, UHC filter,  400 ISO, 2130 sec, left: image processing using fitswork/GIMP; right: image processing using  PixInsight V 1.8.8-5 

End February 2023, almost too late as NGC 2244 was about to “disappear” in the West (the optimum position on the night sky, high in the South, is December/ January), I obtained deeper exposures using the ASI1600mm pro with narrowband filters (S[II], H-alpha, and O[III]). This observation was done with my new ZWO-EAF electronic auto-focuser which produces perfectly focused, round stars - this is a major improvement as up to then focusing was done by visual inspection only. Which is hard, especially if it is cold. The resulting images, H-alpha (b/w), and three-color combination (S[II]+H-alpha + O[III]) are shown below.

Rosette Nebula (NGC 2244), 25, 27 & 28 February 2023, Kempen, William Optics 110 mm APO FLT f/7, ASI1600mm pro, H-alpha filter, 6720 sec, PixInsight V 1.8.9, Top: detail south/east off centre, Bottom: detail north-east off centre.

Top: Rosette Nebula (NGC 2244), 25, 27, 28 February & 1 March 2023, Kempen, William Optics 110 mm APO FLT f/7, 

ASI1600mm pro, H-alpha filter +O[III] filter + S[II] filter, 6840 sec + 7080 sec + 6720 sec, PixInsight V 1.8.9