Monthly
Messier Star-Hop; August #1
By Art
Russell
August normally heralds the "Dog Days" of Summer and brings the hope that cooler days may be ahead. For astronomers, August brings the Perseid meteor showers so be sure to keep an eye out for this often impressive display.
August also marks your last opportunity to observe the greatest concentration of easy to observe Messier ("M") objects as the constellations Scorpius, Ophiuchus, Sagittarius, and Scutum slip pass the zenith and begin their inevitable descent into the western horizon, not to be seen until next year. I encourage anyone interested in getting a running start at their Messier Certificate (contact your local astronomy club or The Astronomical League for additional information).
This month’s star hops will indulge my passion for globular clusters. Of the 147 globular clusters, you'll find that many are concentrated in the constellations Ophiuchus and Sagittarius. In this star-hop, we’ll concentrate on Ophiuchus which lies above both Sagittarius and Scorpius and star-hop to M62, M19, M9, M107, M12, M10, and M14 in seven star-hops.
Star-hop
#1. M62, NGC 6266
Star-hop #2. M19, NGC 6273
Star-hop #3. M9, NGC 6333
Star-hop #4. M107, NGC
6171
Star-hop #5. M12, NGC 6218
Star-hop #6. M10, NGC 6254
Star-hop #7. M14, NGC 6402
A tip to easy observation of these objects is to view from the darkest skies possible and use the lowest power eyepiece you have. All of these objects are visible in binoculars, so don’t hesitate to use yours if you have them as well!
Star-hop #1. M62, NGC 6266. We begin our tour of Ophiuchus’ globular clusters by starting in the constellation Scorpius. First locate the star Antares ("The Rival of Mars"), Alpha Scorpii. Then locate the next star in the constellations figure to the south, Tau Scorpii. Beginning at Tau Scorpii, extend an imaginary line to the star 45 Ophiuchi. M62 is located about half way along, and south of this line. M62 appears very compact and disk shaped, but no stars are resolved in smaller telescopes.
Star-hop #2. M19, NGC 6273. Our next stop is M19. To find M19, return your scope to Tau Scorpii and then extend an imaginary line to the star Theta Ophiuchi. M19 lies a little more than half way along and south of this line, about 60% of the way to Theta Ophiuchi. Like M62, M19 also appears very compact with no resolved stars in smaller telescopes.
Star-hop #3. M9, NGC 6333. Constellation Ophiuchus. Starting at the star Theta Ophiuchi, the next star to the north in the constellation is 44 Ophiuchi. Extend an imaginary line from 44 Ophiuchi to the star Sabik, Eta Ophiuchi. M9 is located about halfway along and just east of the line. M9 appears as a faint, but distinct, unresolved smudge in smaller telescopes.
Star-hop #4. M107, NGC 6171. To locate M107, we once again return to the constellation Scorpius for our starting point. First, locate the star Beta Scorpii recognized as the highest of easily seen "Claws of the Scorpion." From Beta Scorpii, the next star higher in the constellation is Nu Scorpii. Extend an imaginary line from Nu Scorpii to the star Zeta Ophiuchi. M107 lies 3/4 of the way from Nu Scorpii to Zeta Ophiuchi and just to the east of this line. In the club’s 20 inch telescope, M107 appeared as a moderate sized globular with many resolved stars. A number of outlying stars were concentrated toward the west side of the cluster.
Star-hop #5. M12, NGC 6218. Start at the star Zeta Ophiuchi and extend an imaginary line to the star Kappa Ophiuchi. M12 lies a little less than half way from Zeta Ophiuchi to Kappa Ophiuchi and just to the east of this line. In the club’s 20 inch telescope, M12 appears as a moderate sized globular cluster with many resolved stars. There appeared to be a main concentration of stars with a less organized patch apparently in the background to the northwest of the nucleus of the cluster.
Star-hop #6. M10, NGC 6254. Starting once again at the star Zeta Ophiuchi, extend an imaginary line to the star Alpha Ophiuchi. M10 lies about 1/3 of the way from Zeta Ophiuchi to Alpha Ophiuchi and just to the east of this line. In the club’s 20 inch telescope, M10 appeared as a relatively bright, moderate sized globular cluster. However, the cluster did not appear well organized and had many stars trailing away from its nucleus.
Star-hop #7. M14, NGC 6402. To locate M14, extend an imaginary line from the star Sabik, Eta (h ) Ophiuchi, and the star Cheleb, "The Shepherd’s Dog," Beta Ophiuchi. M14 is located not quite 2/3 along the way from Eta Ophiuchi to Beta Ophiuchi, and just to the east of that line. In the club’s 20 inch telescope, M14 appeared as a small to moderate sized globular cluster. Its stars were not well resolved, but the cluster seemed well organized. Additionally, a very faint arm of stars appeared to trail off to the northwest.