IC 4651

OPEN CLUSTER IN ARA (THE ALTAR)

(ra: 07h 17' 24"/ dec -49º 56')

CLICK THE IMAGE FOR A HIGH RESOLUTION VIEW

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

DATA

TYPE: Open Cluster

Visual Brightness: 6.9

APPARENT DIAMETER: 10 arc minutes

DISTANCE: 2900 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: KYWATCHER NEQ6, OAG with QHY 5II Mono

FILTERS:  OPTOLONG LRGB Set

SKY CONDITIONS: Urban Skies, half Moon

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

OBJECT DESCRIPTION AND IMAGE SESSION

IC 4651 is an open cluster of stars located about 2,900 light years distant in the constellation Ara a bit more of 1 degree to the west from magnitude 2.79 alpha arae. It was first catalogued by John Louis Emil Dreyer in his 1895 version of the Index Catalogue. IC 4651 is an intermediate age open cluster that is 1.2 ± 0.2 billion years old. Compared to the Sun, the members of this cluster have a higher abundance of the chemical elements other than hydrogen and helium. The combined mass of the active stars in this cluster is about 630 times the mass of the Sun.

From our perspective IC 4651 is situated in the southern part of the celestial equator and therefore the background is full of stars.

Within the open cluster we have the star IC 4651 9122 displaying radial velocity variations suggesting the presence of a planetary companion, though the stellar activity cannot be completely ruled out