|M4: Globular Star Cluster (Scorpius) RA: 16h 23.5m / DEC -26° 31'.5|
Instrument: 10-inch Starfinder
M4 is among the showpiece globulars of the summer sky. It is easy to find, 1.3 degrees west of 1.0 magnitude Antares. Roughly translated, Antares means the rival of Mars. The Mars opposition of 1999 brought the red planet close enough to its rival to remind contemporary observers how Antares earned its name. On more than one occasion, I politely pointed out that the brilliant red glow in the southern sky was not Mars, but a star.
My drawing is based on a 129X view in the 10-inch Starfinder. M4 appears roughly 30 arc minutes in diameter, equal in apparent size to the full Moon. The central region, 15' in diameter, is laced with curving strings of stars within the globular. All are undoubted old red giants, the only stars that would be visible in moderate aperture from the 5,000 to 6,000 light-year distance at which M4 resides. This central portion is surrounded by a delicate glow reaching almost to the edge of the eyepiece field. The tight grouping of four stars at the northeast boundary range from 8th to 13th magnitude.
Layout, design & revisions © W. D. Ferris
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Revised: July 13, 2004 [WDF]