There is a well-defined list of the most prominent astrophotography targets, and the Rosette nebula in Monoceros has been on this list since the beginning. It has quite significant apparent dimensions, it is quite bright, it has a well-defined structure and a lot of detailed features inside. I have already approached this target a few times, but this is the first attempt with all three narrowband filters – for hydrogen, oxygen, and sulfur elements.

Rosette nebula is also cataloged in Caldwell’s list at number 49. It is a hydrogen region located in the Monoceros region of the Milky Way. There is an NGC2244 open cluster associated with this nebulosity, and this cluster’s stars have been formed from the Rosette nebula matter. Both these targets are located about 5,000 light-years from Earth.

Rosette nebula HSO
Rosette nebula HSO

The NGC2244 cluster age has been estimated to be less than 5 million years. The two brightest members of the cluster are of spectral classes O4V and O5V, about 400,000 times brighter and about 50 times more massive than the Sun. NGC2244 stars are responsible for the Rosette nebula’s glow. Their radiation ionizes the elements in the nebula causing them to emit light.

Rosette nebula HSO - crop
Rosette nebula HSO - crop

Rosette is a very active stellar nursery – many Herbig-Haro objects, Bok globules, and T Tauri-type stars are present. It is much larger than the well-known Orion Nebula (130 vs. 24 light-years), but Orion Nebula is much closer to us, so its apparent size is bigger.

It is a perfect astrophotography target for medium-sized setups, where it fits as a whole into the field of view. But also large setups should be pointed there to reveal details of the Rosette nebula interior. It requires a good seeing, but the outcome will be outstanding.

Rosette nebula center in Ha band
Rosette nebula center in Ha band
Image technical data:

Date: February-March 2023
Location: Nieborowice, Poland
Telescope: TecnoSky 90/540 Owl triplet
Corrector: TS FF/FR 0.8x
Camera: QHY268M
Mount: EQ6
Guiding: ASI290MM + Evoguide ED50
Exposure: 3x6 hours with Baader HSO narrowband filters. Single subframe time was 3 minutes
Conditions: Bortle 6, transparency medium-good, seeing medium