NGC 2204

OPEN CLUSTER IN CANIS MAJOR (THE GREAT DOG)

(ra: 06h 15' 07"/ dec -18º 39')

December 2025, Home Backyard in Martinez, Buenos Aires, Argentina

DATA

TYPE: Open Cluster

Visual Brightness: 8.6

APPARENT DIAMETER: 13 arc minutes

DISTANCE: 1200 light years

IMAGE INFORMATION

SCOPE: 6" ORION OPTICS UK (Ultra Grade Optics) w/Sky Watcher Coma Corrector (0.9x) working at at f4.5

CAMERA: QHY 183 MONO

MOUNT: SKYWATCHER NEQ6, OAG with QHY 5II Mono

FILTERS:  OPTOLONG LRGB Set

SKY CONDITIONS: Urban Skies. Bortle 9

EXPOSURES: LRGB (45,45,45,45) - all channels bin 1x1

OBJECT DESCRIPTION AND IMAGE SESSION

NGC 2204 is an ancient cluster, approximately 2 billion years old, with low metallicity. Its iron content is a meager 59% of that of the Sun. This star cluster contains a significant population of blue straggler stars, an indicator of past stellar mergers. It also contains two candidates for chemically peculiar stars and five variable stars, four of which are eclipsing. NGC 2204 was discovered by astronomer William Herschel on February 6, 1785. In this image, north is at the bottom (*)

Despite the sky surveys there a not many color images of this cluster. This open cluster is very faint and, although a relative bright object, it is quite a challenge to image from Bortle 9 skies

(*) Text extracted form Universo Magico.