|Hickson 93: Galaxy Cluster (Pegasus) RA: 23h 15.3m / DEC: +18° 57'.7|
Instrument: 18-inch Obsession
Five galaxies are gathered in the sketch at left, which presents a 141X view in my 18-inch Obsession. All five are members of Hickson 93. The largest and brightest of the quintet is NGC 7550; Hickson 93A. Its 1' diameter form shines with a blue magnitude of 13.2, suggesting a mid-12th magnitude intensity at the peak of visual sensitivity. It's a transitional-type galaxy stationed some 250 million light-years from Earth, which is the same estimated distance to all but one member of this grouping. A 12th magnitude GSC star shines about 3' to the south.
NGC 7549 (Hickson 93B) is the somewhat irregular haze visible 5' north of NGC 7550. This barred spiral displays a pair of long, distended arms in CCD images. But just the bright inner portion is seen in my 18-inch. The barred core covers 60" by 45" area and is arranged roughly northwest to southeast. A 10th magnitude star simmers 1'.3 to the west. Three arcminutes west of NGC 7550 lies the elongated haze known as NGC 7547 (Hickson 93C). This 14.7(B) magnitude edge-on spiral covers a petite 45" by 30" patch of sky along an east-west axis.
Looking 6' to the east-southeast of NGC 7550, the delicate glow of NGC 7558 (Hickson 93E) is teased from the sky. Best seen with averted vision, this 30" diameter elliptical galaxy has a blue magnitude of nearly 16. This suggests a visual brightness in the low-15th magnitude range. The radial velocity and redshift data suggest a distance of more than 440 million light-years for NGC 7558. I wonder what the smallest aperture needed to see this FLS (faint little stinker) is? Finally, about 6'.5 northeast of NGC 7550, a tiny 20" diameter smudge of light emerges. This is PGC 70842 (Hickson 93D) and presumptively NGC 7553, although that NGC identification is uncertain. This galaxy is just as challenging as nearby NGC 7558.
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Revised: December 4, 2005 [WDF]