Monthly Messier Star-Hop; July#1
By Art Russell

Enough said. Lets get started. As ever, its always best to get as far away from any source of light pollution when viewing deep sky objects. Given these objects' low declinations, its even more important. Invest those few extra minutes to drive a little further out into the country to look for these objects. You'll be well rewarded.

Star-Hop #1: M7 (NGC 6475).
Star-Hop #2: M6 (NGC 6405), the "Butterfly Cluster."
Star-Hop #3: M24 (Mel 197)(the "Small Sagittarius Star Cloud"), M23 (NGC 6494), and M25 (IC 4725).
Star-Hop #4: M18 (NGC 6613), M17 (NGC 6618)(the "Swan or Omega Nebula"), and M16(NGC 6611)(the "Eagle or Star Queen Nebula").

Star-Hop #1: M7 (NGC 6475). We're picking up where we left off last month, in the constellation Scorpius. First things being first, locate Scorpius near the southern horizon. The first indicator that you may be near should be the bright yellow-red beacon that is the star Antares, Alpha (a ) Scorpii, the "Rival of Mars" or the "Heart of the Scorpion." From here, locate the star G Scorpii representing the Scorpion's stinger, about 20 degrees, or the distance spanned by your little finger and thumb spread against the night sky at arm's length, to the southeast of Antares. Before continuing on to M7, be sure to examine the area immediately surrounding G Scorpii for the presence of NGC 6441, a small, moderately bright globular cluster. From G Scorpii, M7 is a little bit more than 2 degrees or twice the distance spanned by your little finger at arm's length against the night sky, to the northeast. M7 is a bright naked eye object. Moreover, you should be able to easily locate M7 by sweeping the area with binoculars or a telescope at low magnification. Binoculars will show M7 as a body of nebulosity with a few resolved stars. Telescopes in progressively larger sizes and magnifications will resolve all of M7's visible stars.

Star-Hop #2: M6 (NGC 6405), the "Butterfly Cluster." Locate M6 by returning to our previous guide star, G Scorpii. Due west 3 degrees, or about the distance spanned by 2 fingers held at arm's length against the sky is the star Shaula, Lambda (l ) Scorpii. Imagine an isosceles triangle pointed north with G Scorpii and Shaula as the east and west apexes, respectively. Extend a line 5 degrees, or the distance spanned by 3 fingers held at arm's length against the night sky, to the north apex of the isosceles triangle to find a beautiful, compact open cluster which is much smaller than M7. Binoculars will resolve a number of stars and suggest a "H" or "Butterfly" pattern. Moderate sized telescopes at moderate magnifications will resolve most of the cluster's stars.

Star-Hop #3: M24 (Mel 197)(the "Small Sagittarius Star Cloud"), M23 (NGC 6494), and M25 (IC 4725).

M24. Our next star-hop takes us from Scorpius to the nearby prominent constellation Sagittarius. Also known as the "Teapot," the heart of Sagittarius is located about 10 degrees, or the distance spanned by your fist against the night sky at arm's length to the northeast of G Scorpii. Having found Sagittarius, locate the star El Nasl, Gamma (g ) Sagittarii. From there, extend a line a little less than 10 degrees, or the distance spanned by your fist against the night sky at arm's length, northeast to find the star Mu (m ) Sagittarii. About half-way there, you may notice a faint patch of nebulosity. Upon examination, you'll discover that it is the small globular cluster NGC 6553. Continuing the line from Mu Sagittarii, for a little more than 2 degrees and you'll arrive at a bright star-cloud buried in the southern Milky Way, M24. Don't be distracted by a dimmer open cluster enroute. This is NGC 6595, but is much less prominent than M24. M24 is visible both as a naked eye object, but is better seen with binoculars. Better still, telescopes at moderate magnifications will reveal an embedded open cluster NGC 6603 which is sometimes mistaken for M24. Keep in mind how to quickly find M24. We'll be using it as a start point for several of the following star-hops.

M23. From M24, extend a line a little more than 4 degrees, or a little less than the area spanned by 3 fingers held together against the night sky at arm's length, west-southwest, and you'll arrive at a bright open cluster which you can easily find when sweeping the area with binoculars. Moderate magnifications will show an open cluster relatively with many stars, some of which may suggest a "ladder" or "picture frame" in appearance.

M25. Once again with M24 as a point of reference, extend a line, except this time a little less than 4 degrees east-southeast and you'll arrive at M25. This cluster may be observed with the naked eye, but is better seen with binoculars where it dominates the view. At moderate magnifications in a telescope, M25 is a pretty and bright open cluster. Several of its stars may appear to form a "bowl" upon closer examination, but take a look and make up your own mind. What do you see?

Star-Hop #4: M18 (NGC 6613), M17 (NGC 6618)(the "Swan or Omega Nebula"), and M16(NGC 6611)(the "Eagle or Star Queen Nebula").

M18. Using M24 as our starting point once more, extend a line north-northeast for a little more than 1 degree, the distance spanned by your little finger against the night sky at arm's length. Here you'll find a small, moderately bright patch of nebulosity. The cluster is visible in binoculars, but it really doesn't shine until you examine it with a telescope at moderate magnifications. Take the time to enjoy this often overlooked gem in Sagittarius.

M17. From M18, extend a line 1 degree north-northeast. Here you'll find a cluster which appears a bit brighter than M18. Additionally, in binoculars and smaller telescopes you may notice the suggestion of embedded nebulosity which you may mistake for unresolved stars. Not so in this case. Examine this open cluster closely because it is has its own associated nebula and is one of the better known objects seen in the summer Milky Way from the northern hemisphere. Moderate to high powers, and / or narrow-band ("nebula") filters will help you to best observe this pretty object. Under the right conditions, M17 may resemble the letter "P."

M16. The final jump in this star-hop takes us to another of the prominent nebulae in the southern summer Milky Way. At close examination you may recognize is as one of the recent targets for the Hubble Space Telescope. While we don't have access to the same resources as NASA, its nice to know that we can get a pretty good view for considerably less money!! From M17, extend a line a little more than 2 degrees to the north-northwest and into the constellation Serpens Cauda. Scan this area with your binoculars and you'll easily find M16. However, binoculars won't do this object justice. Like M17 previously, try to observe M16 with a telescope at moderate to high magnifications and possibly nebular filters for the best possible view. Don't dare miss this object. Miss any of the others. Not this one!