|SFAA Glacier Point
Observations for July 19-21, 2012 Star Parties
This list is not necessarily for the public viewing, but to pique your interest for more challenging objects.
Tonight we have a baker’s dozen of interesting objects in the constellations of Cygnus, Vulpecula, Sagittarius, and Scorpius. While the emission nebulae targeted benefit from the use of OIII or dark sky filters, these objects are also quite nice without them. So go for it! Ess Eff A Aers.
Cygnus (S&T Pocket Sky Atlas – pg 62)
This cruciform-shaped constellation is prominently on display high in the eastern sky, just east of the star, Vega. The bright star, Alpha () Cygni, commonly known as Deneb, is one of three points of the well-known Summer Triangle. The other point stars are the stars Vega, in Lyra, and Altair, in Aquila. Cygnus is also home to Albireo, one of the most beautiful double stars in the sky.
Messier 29 is a 6.6 magnitude open cluster located about 4,400 light years away. Scopes may see up to 80 stars packed into a tiny 10’ circle of sky. Unfortunately, the cluster is somewhat obscured by a curtain of gas and dust between the cluster and our scopes. This cluster seems best observed through small to moderate sized scopes at low magnification. To locate this cluster, center Cygnus’ heart-star, Sadr, in your eyepiece, then slide southward until it comes into view.
Messier 39 is another open cluster located about 950 light years distant. It is a sparse cluster, with 30 stars scattered across an area the size of a full Moon. Under a dark sky M39 may be seen with the unaided eye about 9 degrees east-north-east of Deneb, and the pure bluish cast of the primary stars are certainly a pretty sight in binoculars.
NGC 6888 is the visible shock wave of a stellar wind blowing from a rare Wolf-Rayet star, and colliding with a previous, slower moving expulsion of gases ejected from the star about 400,000 years ago. These gases-in-collision emit light, and are what you are seeing. The crescent is about 5,000 light years distant.
Vulpecula (S&T Pocket Sky Atlas – pg 62)
This constellation is rather obscure, but our target, M27, the Dumbbell Nebula, is an easy find. The trick is to draw an imaginary line from the star Albireo southward to the tiny four-star arrowhead of Sagitta. Now move upward along the line to it’s mid-point, then scan about ½ the line length to the east, and Voila!
Messier 27 is one of the brightest planetary nebulae in the sky. Easily spotted in most binoculars, this 7th magnitude object is 815 light years away. About 48,000 years ago a star similar to our own went through its death throes, puffing away multiple layers of gaseous material, one at a velocity of 9 miles per second, and another at 20 miles per second. The shells now extend outward to about 1.2 light years from the very faint white dwarf progenitor. This object responds well to both OIII and various deep sky filters. A neighbor may be using one, so ask for a peek for comparison.
Sagittarius (S&T Pocket Sky Atlas – pg 67)
This constellation is easily found just east of the scorpion’s stinger. While Mythology identifies it as an archer, we see it as an obvious teapot with steam (the Milky Way) drifting upward from the spout. We’ll observe some of the magnificent objects in the vicinity of the teapot, then pick up the remaining jewels next moth.
Messier 22 is an outstanding 5th magnitude globular cluster. Over 500,000 stars make up this teeming conglomeration of lights that extends across about 33’ of sky. Situated only 10,000 light years away, M22 is one of the nearest globulars to us. Look just to the left of the top star in the teapot lid (Kaus Borealis) and there it is. In his work, The Hobbit, J.R.R. Tolkien described M22 thus, “if a globe had been filled with moonlight and hung before them in a net woven of the glint of frosty stars.” Even amongst the Messier objects, this one is a keeper.
Messier 28 is a 7th magnitude globular cluster drifting about 20,000 light years away. With an apparent diameter of only 10’. M28 is just a shade of M22, but well worth finding. From the top teapot star, Lambda (λ) Sagittarii, move about 1 degree northwest to this little globular. With moderate magnification, look for a color difference that has been recorded by many observers. To some, the core has a distinct pale yellow cast, while the halo is a pale blue. What do you see?
Messier 17 is my favorite emission nebula in Sagittarius. Commonly known variously as the Omega, Swan, or Horseshoe Nebula, it resides about 4,900 light years away. M17 is a relatively large object at 40’, with a combined magnitude of 6, and is generally found by trolling up the Milky Way steam cloud from M20 until you find it. M17 is my favorite because new observers tend to see it differently. My first impression through an 80mm refractor was of a glowing checkmark, while others may see an obvious swan. Much depends on the size of scope you are using, so take time to wander about for peeks through your neighbor’s scopes. Most deep sky filters work well on M17.
Messier 8 is a combination of an open star cluster and a bright, magnitude 4.6, emission nebula located about 5,200 light years away. Visible to the unaided eye, M8 resides in the vapor seen rising from the Teapot’s spout. Commonly known as the Lagoon Nebula, M8 displays apparent dark channels that weave throughout the glowing gas. Since the nebula extends over one degree in apparent size, use the lowest magnification you have available for the best view of this fascinating object. OIII and Deep Sky filters work well on the Lagoon.
Messier 20 is another bright cluster/nebula combination, and is very near to M8 in the sky. In fact it is somewhat nearer to us, at a distance of 5,000 light years. M20 is considerably smaller than the Lagoon. Look for an object about 20’ in extent. In my 4” scope at 23x, I can view both M8 and M20 in the same field of view. Commonly known as the Trifid Nebula, close inspection will reveal several dark lanes that roughly split the glowing cloud into three major (some say four) portions. As with M8, OIII and Deep Sky filters work well here.
Messier 54 is a small globular cluster that is about 70,000 light years away, placing it as the most distant of all the Messier globulars. With a combined magnitude of 7.7, M54 is found by tracing a line along the base of the teapot. From the handle-star, Zeta (ζ) Sagittarii, slide your scope about 1/5th of the way along the baseline and slightly into the interior of the pot. Some folks find it immediately, while others have a more difficult time of it.
Messier 70 is another globular cluster about 35,000 light years away. With an apparent diameter of only 8’ it would seem to be a more difficult target than M54, but because it sits astride that imaginary line along the base of the teapot, I pick it up rather easily through my 4” scope. In small scopes at low magnification, M70 is sometimes first identified as a small spiral galaxy. It isn’t.
Scorpius (S&T Pocket Sky Atlas – pgs 56 & 58 )
This constellation is best located by looking southward to the familiar scorpion shape, then locating the bright red star, Antares. This red supergiant represents the heart of the easy-to-recognize scorpion.
Messier 4 is a 5th magnitude globular cluster that may be seen in the same FoV with Antares at low magnification. M4 is 6800 light years distant, and has an apparent diameter of 35’ in photos. The actual diameter of M4 is 70 light years. This globular takes magnification well, so increase power and look for indications of a bright central bar extending across the disk, which accounts for the oft mentioned moniker, the Cat’s Eye.
Messier 80 is another globular cluster, shining at magnitude 7.3. M80 is located 27,000 light years away, which accounts for it’s small apparent diameter of only 9’. What it lacks in apparent size, it certainly makes up in stellar density. Find M80 by moving about 4.5° northwest of Antares. Star-hoppers can draw an imaginary line from Antares to the star Graffias, Beta (β) Scorpii. M80 is nearly halfway between the two stars.
Saturn is still found in the constellation Virgo, currently drifting toward the western horizon. Saturn’s rings are now tilted to highlight the famous Cassini Division. A close look may disclose one of the white storm clouds that have been observed lately. Saturn is always an attention-getter and is worth some quality eyepiece time. Observe it before it drifts into the twilight
This month’s challenge object is the Bridal Veil Nebula in Cygnus. This extended object is also known as the Cygnus Loop. Composed of NGC 6960, 6992 and 6995, this large collection of nebulosity is the result of a supernova explosion about 2,500 light years distant that occurred some 15,000 years ago.
This type II supernova marked the final chapter in the life of a supergiant star with an original mass at least eight times that of our Sun. As the fusion process eventually progressed to the element, Iron, all fusion stopped, gravity took over, and in seconds, the star collapsed into a sphere approximately 10 km across. The blast destroyed the star and spewed its remains outward into deep space at a velocity of several thousand kilometers per second. The long streamers of nebulosity we see today are remnants of the still-expanding shell that are now colliding with clouds of interstellar gas, The resulting shock wave is primarily responsible for the emission nebulae we see today.
Some observers have never seen the Cygnus Loop and feel that it is too difficult for their scope, but if you have an 80mm refractor, a 4.5” reflector, or anything larger, you can capture the Loop. The primary requirement for a quality look is a wide field of view, which actually favors the smaller scopes. Page 62 of Sky and Telescope’s Pocket Atlas, will be a great asset in reaching your targets.
Begin your search by inserting your lowest magnification eyepiece, then locate the star Sadr, Gamma (γ) Cygni, which is the heart star of the swan. Now move eastward to the first star in the wing, Epsilon (ε) Cygni. Now move slightly southward to 52 Cygni. This star seems to be immersed in the beautiful swath of glowing gas known as NGC 6960. I’ve found that the easiest method for finding the other remnants is to imagine the arched shape of NGC 6960 as a partial ring of water resulting from a pebble tossed into a pool, then imagine the direction to the center of the ring. Now move your scope in that direction until you encounter the more extensive, intertwined arcs of NGC 6992 and 6995. Along the way, slightly to the north, you will no doubt encounter a triangular gas cloud known as Pickering’s Wedge.
This fine observing list was adapted from Sierra StarGazers member Forrest Lockhart.
Thank you Forrest!