OPEN CLUSTERS included in "EYEPIECE" Program - Part 1 Copyright (c) 1991-2007, Stephen R. Waldee - All Rights Reserved This is a selected listing of open clusters, with descriptions, taken from deep sky objects contained in our software program Eyepiece, which altogether features in its databases more 1,000 celestial objects and multiple stars. These selections include the items that had informative commentary, originally prepared from notes of observations by the author, made during the late 1970s and the 1980s at his site on private property in the mountains south of San Jose, California, at 3,400 feet altitude, augmented with brief quotes by observer and amateur astrophotographer John Sanford, copied with the author's permission from his book Observing the Constellations by John Sanford (Fireside / Simon & Schuster), a now out-of-print observing guide that we have used since its publication in 1989. Objects are listed in ascending order of right ascension; all open clusters in the program's database are included as a list available from the menu below (with coordinates and other data.)   Selected Open Clusters that have featured commentary: NGC-188  |  NGC-457  |  M-103  |  NGC-869  |  Stock 2  |  NGC-957  |  M-45  |  Melotte 25 NGC-1907  |  M-38  |  Collinder 69  |  M-36  |  M-37  |  NGC-2158  |  M-35  |  NGC-2169 NGC-2174  |  NGC-2244  |  NGC-2264  |  M-41  |  M-50  |  M-47  |  M-46  |  M-93  |  M-48 M-44  |  M-67  |  Melotte 111  |  M-6  |  IC-4665  |  M-7  |  M-23  |  M-21  |  M-24  |  NGC-6603 M-16  |  M-18  |  M-25  |  IC-4756  |  M-26  |  M-11  |  NGC-6791  |  Collinder 339  |  NGC-6819 Harvard 20  |  M-29  |  NGC-6939  |  M-73  |  M-39  |  NGC-7209  |  NGC-7243  |  M-52 NGC-2169  |  References & Credits  |  Complete Cluster List with data Open Clusters NGC 188: Open Cluster in CEPHEUS Dreyer Summary (NGC): Cluster, Very Large, Round, 150 to 200 Stars from 10th to 18th Magnitude. The faintest stellar magnitudes recorded by 18th and 19th century observers such as the Herschels are usually calculated by modern techniques to be considerably brighter; the old visual astronomers generally reckoned their faintest magnitude stars to be ones that were "just visible" in their telescopes. There are nearly 600 stars in this grouping, of which a few dozen of the brightest will be resolved in scopes of 8 - 10 inches of aperture. A scattering of stars at 13th magnitude will be evident in 17.5 inch aperture scopes; high power will "dissolve" the clustering effect.             Click for Deep-Sky Browser Page for NGC-188.             Click here for Jaakko Saloranta's observation             and drawing. NGC 457: "The Owl" Open Cluster in CASSIOPEIA Dreyer Summary (NGC): Cluster, Bright and Large, Pretty Rich, of Stars from 7th and 8th to 10th Magnitudes. With M103, among the finest of open clusters in the rich region of Cassiopeia. Note the yellow and blue stars Phi 1, 2 Cassiopeiae just south of the cluster; a red star is to the north. Many observers have found this distinctive grouping to have an uncanny resemblance to a tufted owl with its wings outstretched (click here for Jaakko Saloranta's drawing, which 'connects the dots' in a way that helps one to visualize the creature.)             Click for Deep-Sky Browser Page for NGC-457.             Click here for Jaakko Saloranta's observation             and drawing. NGC 581 - M103: Open Cluster in CASSIOPEIA Dreyer Summary (NGC): Cluster, Pretty Large, Bright, Round, Rich. 10th to 11th Magnitude Stars. One of the crown jewels of the constellation, M103 can easily be discerned in the same binocular field with Delta Cassiopeiae, in the flatter "triangle" of Cassiopeia's famous "W", and is therefore a good choice for beginning observers. A red central star and other colored members will be apparent in apertures of 4 - 6 inches.             Click for Deep-Sky Browser Page for M-103.             Click here for Jaakko Saloranta's observation             and drawing. NGC 663: Open Cluster in CASSIOPEIA Dreyer Summary (NGC): Cluster, Bright, Large, Extremely Rich, Stars Pretty Large [i. e. bright]. John Sanford describes NGC 663 as a very rich cluster in the same general neighborhood in which several Struve catalog double stars are located. Struve 163 -- a lovely contrasting reddish-gold and blue double -- is included in the double star datafile of "EYEPIECE", and is about 5 degrees from NGC 663. Large aperture scopes will show the faint colors of some members of the cluster. The object is also known as Caldwell 10.             Click for Deep-Sky Browser Page for NGC-663.             Click here for Jaakko Saloranta's observation             and drawing. NGC 869/NGC 884 - "Double Cluster" in PERSEUS Dreyer Summary (NGC): 869 is a Remarkable Cluster, Very Large and Rich, Stars from 7th to 10th Magnitude. 884 is a Remarkable Cluster, Very Large and Rich, with a Ruby-Colored Star in the Middle. Few photographs do justice to the sparkling beauty of these fairly well-matched clusters, arranged close in the same field in almost any instrument. A nebulous patch to the naked eye, the Double Cluster resolves into stars with binoculars; a large aperture telescope with a modern wide-field eyepiece providing a field of view of about 1.5 to 2 degrees will be ideal for enjoying the totality of the experience. Bright stars predominate, with a central peppering of very faint stellar spots in the western member 869, while 884 is slightly looser and features the lovely ruddy star RS Persei.             Click for Deep-Sky Browser Page for NGC-869. Stock 2 (OCL 348, Lund 71): "Muscle Man" Open Cluster in CASSIOPEIA This charming group of four dozen stars jumps into view as a distinct arrangement because of its apparent resemblance to a human figure, and has been nicknamed the "Muscle Man" cluster by Philip Harrington in "Touring the Universe Through Binoculars." Most of the stars are near 8.5 magnitude, and in a very wide field as provided by a richest field scope or binoculars, the grouping -- which is more than a full degree in diameter -- should stand out even in moderately light-polluted skies. Look for the "Muscle Man" about 2 degrees north of the Double Cluster.             Click for Deep-Sky Browser Page for Stock 2.             Click here for Jaakko Saloranta's observation             and drawing. NGC 957: Open Cluster in PERSEUS Dreyer Summary (NGC): Cluster, Pretty Large and Rich, Stars of 13th to 15th Magnitude. After viewing the famed "Double Cluster" in Perseus, swing your scope or binoculars about one degree east to this smaller open cluster. This loose arrangement of about 40 visible stars includes at least one double star about two magnitudes brighter than the surrounding members.             Click for Deep-Sky Browser Page for NGC-957. NGC 1039 - M34: Open Cluster in PERSEUS Dreyer Summary (NGC): Cluster, Bright, Very Large, Little Compressed. Scattered Stars of 9th Magnitude. John Sanford description: "a fine open cluster which can just be glimpsed with the naked eye. It lies on a line almost halfway between Algol and Gamma Andromedae, the easternmost bright star in the group. It contains about 80 stars in the half-degree diameter, including several pairs."             Click for Deep-Sky Browser Page for M-34.             Click here for Jaakko Saloranta's observations             and drawings. Melotte 22 - M45: "The Pleiades" Open Cluster/Reflection Nebula in TAURUS Dreyer Summary (NGC): Not Included in NGC List Not an object cataloged by Dreyer in the NGC or IC, the ancient name for this group -- The Seven Sisters -- was not a particularly accurate description, for almost twice this number of stars may be glimpsed by keen naked-eye observers in a dark sky. An asterism shaped like a dipper may be seen in the smallest optical instruments, with numerous fainter stars appearing as the size of the aperture is increased. It may be necessary to use a visual exit pupil in excess of 7 mm in order to obtain the wide field necessary to appreciate the totality of the cluster. Binoculars, a richest-field scope, or even a good finder- scope will give the proper perspective to this beautiful aggregation. The renowned nebulosity of the Pleiades, discovered visually by comet- hunter Wilhelm Tempel in 1859, and confirmed photographically in 1885, may be spotted on nights of exceptional atmospheric clarity by using high-resolution optics and employing a broadband LPR filter, to accentuate the reflection nebulosity around the stars Merope, Alcyone, and some of the other bright stars in the cluster. Do not be mistaken by reflections, flaring, and light scattering around the bright stars.             Click for Deep-Sky Browser Page for Messier 45.             Click here for author Waldee's article on observing M45.             Click here for Jaakko Saloranta's observations             and drawings. NGC 1502: Open Cluster in CAMELOPARDALIS Dreyer Summary (NGC): Cluster, Pretty Rich, Considerably Compressed, Irregular Figure. One of the few open clusters in this constellation, NGC 1502 is a bright grouping which includes a central double star of about 18 arcseconds separation. More than half of its 63 stars are easily visible in large amateur scopes.             Click for Deep-Sky Browser Page for NGC-1502.             Click here for Jaakko Saloranta's observation             and drawing. Melotte 25: "The Hyades" Open Cluster in TAURUS John Sanford description: "The Hyades is one of the nearest open clusters to the Solar System...astronomers have found the cluster is receding towards a point east of Betelgeuse...The Hyades contains many stars which have evolved for a longer time than the Pleiades. The age has been estimated at 400 million years...Some fine doubles are found here. Chi is north of the "V" shape in Taurus. Kappa + 67 are two yellow stars 339 arcseconds apart with a delicate double" (see the double star section of the program for the constellation Taurus.) The eye of the Bull is bright, red Aldebaran, which shines at a brilliant magnitude of 0.86, but is closer to us than the members of the cluster. Telescopic viewers must be content to scan across this enormous region of sky, which will not fit into the field of view of typical instruments.             Click for Deep-Sky Browser Page for Melotte 25. NGC 1907: Open Cluster in AURIGA Dreyer Summary (NGC): Cluster, Pretty Rich, Compressed, Round, Stars of 9th to 12th Magnitudes. This galactic cluster makes a small but rich and handsome companion to M38 (below) and stands out well from the background stars even in a telescope of 4 inches aperture. Using an ocular of wide angle design, M38 and NGC 1907 may be observed in the same field of view. A central dense region is noted in larger instruments.             Click for Deep-Sky Browser Page for NGC+1907.             Click here for Jaakko Saloranta's observation             and drawing. NGC 1912 - M38: Open Cluster in AURIGA Dreyer Summary (NGC): Cluster, Bright, Very Large, Very Rich. With Irregular Figure, Large and Small Stars. John Sanford's description: "...a large open cluster which has streams of stars leading into a rather dark middle. This is a rich neighborhood, with the smaller galactic cluster NGC 1907 almost directly south." Because of the "palpable cruciform" asterism in the central region of M38, Admiral Smyth recalled Wm. Herschel's speculations on the gravitational attraction of stars in such groupings. However, other observers -- including Messier -- have not noticed such an arrangement.             Click for Deep-Sky Browser Page for Messier 38.             Click here for Jaakko Saloranta's observation             and drawing. Collinder 69: Open Cluster in ORION Acute naked-eye observers may discern something of a nebulous patch in this spot, which optical aid resolves into a sparkling group. Especially suited to widefield instruments such as binoculars and short-focus telescopes, this cluster of stars surrounds the "head" of Orion's hunter, the bright third-magnitude star Lambda Orionis, described by Admiral Smyth as "a pale but clear yellow."             Click for Deep-Sky Browser Page for Collinder 69.             Click here for Jaakko Saloranta's observation             and drawing. NGC 1960 - M36: Open Cluster in AURIGA Dreyer Summary (NGC): Cluster, Bright, Very Large and Very Rich, Little Compressed. Stars 9th to 11th Magnitude, Scattered. M36 and M37 in Auriga, along with M35 lying just outside Gemini, the constellation to the east, are excellent objects for study even in light-polluted city skies, for they are readily discernible in an 80-millimeter aperture instrument. With sufficient aperture, the color contrasts in a number of bright members of the cluster will be apparent. In the same low to medium power field, M36 will be accompanied by the larger yet dimmer M38.             Click for Deep-Sky Browser Page for Messier 36.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2099 - M37: Open Cluster in AURIGA Dreyer Summary (NGC): Cluster, Rich, Pretty Compressed in the Middle, With Large and Small Stars. M37 is beautifully resolved as a broad expanse of faint stars in an 80 millimeter scope, but really shines in apertures of 5 inches or larger. Then, a red giant star near the center is bright enough to the eye to register its color in contrast to the pale white surrounding stars. In a superb instrument with perfect stellar resolution, the overworked cliche "diamond dust" seems the only apt description!             Click for Deep-Sky Browser Page for Messier 37.             Click here for Jaakko Saloranta's drawing             with 3" refractor at 40x. NGC 2158: Open Cluster in GEMINI Dreyer Summary (NGC): Cluster, Pretty Small and Much Compressed, With an Irregular Triangle of Extremely Small Stars. John Sanford description: "Two contrasting galactic clusters appear in one wide-field view (30 arcminutes) in western Gemini. These are the small, condensed, almost globular-looking NGC 2158, which is visible through the outside fringes of M35, an outstanding and large object." (N35 not shown here, but is seen below.)             Click for Deep-Sky Browser Page for NGC-2158. NGC 2168 - M35: Open Cluster in GEMINI Dreyer Summary (NGC): Cluster, Very Large, Considerably Rich, Pretty Compressed. Stars from 9th to 16th Magnitude. John Sanford calls M35 "an outstanding and large object...just at the toe of the more northern Twin, 2.5 degrees northwest of Eta Geminorum. This glorious grouping of several hundred stars has many loops and lines of stellar points in a medium-sized telescope." The crown of Gemini, M35 is one of the most beautiful of winter objects. Also look for NGC-2158, about 1.5 degrees to the southwest, a small and faint cluster that is inconspicuous in poor skies or with small scopes, but worth exploring with larger apertures.             Click for Deep-Sky Browser Page for Messier 35.             Click here for Jaakko Saloranta's observations             and drawings. NGC 2169: Open Cluster in ORION Dreyer Summary (NGC): Cluster, Small and a Little Rich, Pretty Much Compressed, With A Double Star. John Sanford description: "...a fine example of an open cluster, in the northeastern part of the constellation where the winter Milky Way flows by. It's easily found by making an isosceles triangle southwestwards between Xi and Nu." There are about two dozen stellar members, with the brightest being a double star, separating a magnitude 7.4 and a magnitude 8.0 star by only 2.5 seconds of arc.             Click for Deep-Sky Browser Page for NGC-2169. NGC 2174/5: Open Cluster and Diffuse Nebula in ORION Dreyer Summary (NGC): Nebula 2174 is Extremely Faint, Between 3 Very Faint Stars. Cluster 2175 has 8th Magnitude Stars in the Nebula. John Sanford description: "The cluster and nebula NGC 2174-5 are attractive subjects, appearing very red in photographs as many hydrogen emission nebulae do." To the eye, however, the nebulosity will be of the palest grey, and will benefit from a general nebula- line filter, which increases the contrast of hydrogen emission but will slightly dim the starlight of the cluster. Use a large exit pupil and low powers -- or a richest-field scope -- to best effect.             Click for Deep-Sky Browser Page for NGC-2174.             Click here for author Waldee's updated 2006 observation. NGC 2244: Open Cluster Associated with Rosette Nebula in MONOCEROS Dreyer Summary (NGC): Cluster, Beautiful Scattered Stars, Around 12 Monocerotis. John Sanford description: "Another large area of star formation, clustering, and gas is the formation NGC 2233 and its surrounding gas cloud called the Rosette Nebula...a soft glow surrounding the distinc- tive parallelogram of the star cluster in 20 X 80 binoculars or a rich- field telescope. A nebular or light pollution rejection filter will make the [nebula] easier to see." The authors of this program have always found the cluster a delightful sight with even the smallest scopes, and while the nebula has been detected in a dark sky by means of a UHC or OIII filter at low power in an 80 mm (3 inch) aperture scope, it requires perhaps at least 7 - 8 inches of aperture (preferably a wide field instrument), the proper exit pupil, and nebular filter, to fully appreciate.             Click for Deep-Sky Browser Page for NGC-2244.             Click here for author Waldee's updated 2006 observation.             Click here for Jaakko Saloranta's observations             and drawings. NGC 2264: "Christmas Tree" Open Cluster + Nebula in MONOCEROS Dreyer Summary (NGC): Extremely Large Nebula, 3 Degrees Diameter, Densest 12 Minutes South Preceding 15 Monocerotis John Sanford description: "S Monocerotis is a slightly variable blue supergiant with an 8.5 magnitude companion some 3.0 arcseconds distant. S, or 15 Mon, is at the north end of the 'Christmas Tree' cluster, a group of largely B stars (young) imbedded in dense nebulosity which glows from their presence." Use a filter of LPR or UHC type to see the nebulosity with improved contrast.             Click for Deep-Sky Browser Page for NGC-2264. NGC 2287 - M41: Open Cluster in CANIS MAJOR Dreyer Summary (NGC): Cluster, Very Large, Bright, Little Compressed, 8th Magnitude and Fainter Stars. John Sanford's description: "...visible to the naked eye, located where you would find the Dog's heart. It contains several fairly bright stars and multiples. The cluster is almost half a degree in diameter, so is best seen with low powers." Easy to find by sweeping about 4 degrees south of Sirius in a region not otherwise densely populated by bright stars, M41 is a winter spectacle for modest instruments. Larger ones will reveal the ruddy glow of a bright K-type red giant star near the central area.             Click for Deep-Sky Browser Page for Messier 41.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2323 - M50: Open Cluster in MONOCEROS Dreyer Summary (NGC): Remarkable. Cluster, Very Large, Rich, Pretty Compressed, Extended. 12th to 16th Magnitude Stars. John Sanford description: "...a large star cluster in southern Monoceros, with an integrated magnitude of 6.3. It consists of about fifty stars in an area about 10 arcminutes in diameter...a good cluster for small instruments, and is located halfway between Sirius and Procyon in the night skies." On 6 December 2007, author Waldee looked at M50 with his Celestron C-11 telescope, reporting "very large. Sparse, about 2 dozen very bright stars, with more inside and out of the main oval arrangement of about 10 bright ones. There is a striking triangle of stars near the middle. The star HIP 33959 (7.8 magnitude, about 4 minutes south of the cluster's center) seems distinctly yellow-orange at 88x."             Click for Deep-Sky Browser Page for M-50.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2362: Open Cluster in CANIS MAJOR Dreyer Summary (NGC): Cluster, Pretty Large, Rich, Around 30 Majoris. John Sanford description: "NGC 2362 is a beautiful cluster of several dozen stars gathered around 4th-magnitude Tau, which is a wonderful triple star. Although rather low for some northern observers, this cluster is a neglected showpiece of the skies."             Click for Deep-Sky Browser Page for NGC-2362.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2422 - M47: Open Cluster in PUPPIS Dreyer Summary (NGC): Cluster, Bright, Very Large, Pretty Rich, With Large and Small Stars. John Sanford description: "M46 (NGC 2437) lies just following M47, and is a cloud of small stars. The two clusters make a nice contrast, with M47 a coarse, sparser grouping and M46 a richer, but fainter cluster." A good selection for viewing with a small beginner's telescope, which should portray about half of its 50 stars. On 5 December 2007, S. Waldee observed M47 with his C-11 scope: "Huge cluster features three blindingly bright stars in a large triangle, with 5th and 7th magnitude stars to the east and south, and a 6.9 magnitude multiple system (STF 1121) slightly to the north of the center. Three widely spaced apparent doubles in a semi-circle are positioned to the southeast of the center, striking features at low to medium magnification."             Click for Deep-Sky Browser Page for Messier 47.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2437 - M46: Open Cluster (With Planetary Nebula NGC 2438) in PUPPIS Dreyer Summary (NGC): Remarkable. Cluster, Very Bright, Very Rich, Very Large, Involving a Planetary Nebula John Sanford description: "If you look closely at M46 you'll see a 50- arcsecond-diameter planetary nebula among the stars in its northeast quadrant. With 8-inch (20-cm) telescopic apertures and above you can see that it is a round nebula, with the three stars projected upon it. In fact, the nebula is about twice as far away as the cluster, and they just happen to be in our line of sight together." The uniformly- distributed stars will nearly fill the field of view at the high powers required for scrutinizing the small planetary nebula that is likely closer to us than the cluster stars. Look for the planetary nebula NGC-2438 (07d 41m 51.43s RA, -14 43 54.9 dec), which glows distinctly "inside" the northern periphery of M-46 (though it is most likely a foreground object), which will stand out better by using a filter of LPR, UHC, or OIII type.             Click for Deep-Sky Browser Page for Messier 46.             Click here for author Waldee's comments               about the planetary nebula. NGC 2447 - M93: Open Cluster in PUPPIS Dreyer Summary (NGC): Cluster, Large, Pretty Rich, Little Compressed, Stars of 8th to 13th Magnitude. John Sanford description: "...another bright cluster in the rich Milky Way which runs through Puppis. It's a compact group of about 50 bright stars lying 9 degrees south of M46-7." A rich galactic cluster that stands out from a plethora of stars when sweeping the region with binoculars or richest-field scope.             Click for Deep-Sky Browser Page for Messier 93.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2548 - M48: Open Cluster in HYDRA Dreyer Summary (NGC): Cluster, Very Large, Pretty Rich, Pretty Much Compressed Toward Middle. 9th to 13th Magnitude Stars. John Sanford description: "M48 is a fine open cluster situation on the outskirts of the Galaxy, at the western boarder of the constellation. It makes an equilateral triangle with Procyon and the small asterism at the head of Hydra. This group of about 50 stars can be seen as a tiny spot with the naked eye, and presents a lovely field in a low-power eyepiece. There are several yellowish stars seen together with mostly white ones, making a beautiful impression."             Click for Deep-Sky Browser Page for Messier 48.             Click here for Jaakko Saloranta's observation             and drawing. NGC 2632 - M44: "Beehive" Open Cluster in CANCER Dreyer Summary (NGC): Praesepe Cancri Pre-telescopic observers universally recognized M44 as a nebulous patch in the sky. With a very small telescope at least three dozen stars are visible across a wide field. Since Praesepe is a naked-eye object, it is one of the easiest Messier object to locate with a telescope, but -- sadly -- beginners with inexpensive refractors will find that its 95-arcminute-diameter will not fit into the available field of view. Binoculars or richest-field scopes are recommended. Since M44 has a diameter of 95 minutes, about three times that of the Moon, it was impractical to download the data from the Digital Sky Survey to prepare a picture. So, the image above, in very wide scale of at least five degrees -- comparable to what one might see in binoculars -- was prepared by a star chart program, realistically plotting all the stars of the field down to about 9th magnitude. There are many faint galaxies seen 'through' M44 and found around it periphery, a challenge for advanced observers. The bright stars of the cluster make these faint fuzzies hard to discern, though author Waldee has seen many of them with 10 and 11 inch scopes.             Click for Deep-Sky Browser Page for Messier 44.             Click here for author Waldee's 2006 observations.             of galaxies in the vicinity of M-44.             Click here for Jaakko Saloranta's observations             and drawings. NGC 2682 - M67: Open Cluster in CANCER Dreyer Summary (NGC): Remarkable. Cluster, Very Bright, Very Large, Extremely Rich, Little Compressed, 10th Magnitude Stars. John Sanford description: "...a total magnitude of 6.9, and is just beyond naked-eye visibility. To be resolved it requires binoculars, but to appreciate its magnificence, a 6- or 8- inch (15- or 20-cm) aperture telescope is needed. It is elongated in an east-west direction and there is a prominent dark space in the middle near the eastern end."             Click for Deep-Sky Browser Page for Messier 67.             Click here for Jaakko Saloranta's observation             and drawing. Melotte 111: "Coma Berenices Open Cluster" in COMA BERENICES A naked-eye nebular patch that resolves into a myriad of sparklers with the most modest optical aid. This dense 5-degree patch of stars from magnitudes 5 to 6 was charted by the great naked-eye observer Tycho Brahe as "Berenice's Hair"; had he access to a telescope like Galileo's, the 80 stars of the cluster would have astonished him with their richness. However, modern observers are admonished to use their binoculars, finderscope, or widest possible richfield instrument to appreciate the clustering effect, which is lost at narrower fields and higher magnifications. The picture shown here was, in fact, a star field simulation done by a planetarium program, plotting the cluster in a wide region of about 7 degrees of sky, comparable to the view in binoculars.             Click for Deep-Sky Browser Page for Melotte 111. NGC 6405 - M6: Open Cluster in SCORPIUS Dreyer Summary (NGC): Cluster, Large, Irregularly Round. Loosely Compressed. Stars from 7th to 10th Magnitude. An apparently nebulous patch without optical aid, it resolves into a bright cluster of stars even with 3X opera glasses. With a 3" aperture instrument, M6 displays a half-dozen bright stars with about three to four dozen more across the field. A distinct parallelogram, much like a miniature version of the naked-eye stars of the constellation Lyra, is arranged by four of the most luminous members. BM Scorpii, a slow variable red star, stands out dramatically in this arrangement of suns. Best viewed by a small instrument or a richest-field telescope.             Click for Deep-Sky Browser Page for Messier 6.             Click here for Jaakko Saloranta's observation             and drawing. IC 4665 - Open Cluster in OPHIUCHUS Dreyer Summary (Index Catalog): 2 Stellar Nebulosities Suspected. Like many of the objects in the Index Catalog, this grouping must have eluded the visual observers who contributed to the earlier NGC. However, the cluster is a gratifying object, just visible as a hazy patch to the naked eye, and resolving into over two dozen bright bluish stars with a richest-field instrument or large binoculars. The nebulosities mentioned in the IC may have been optical reflections or artifacts.             Click for Deep-Sky Browser Page for IC-4665.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6475 - M7: Open Cluster in SCORPIUS Dreyer Summary (NGC): Cluster, Very Bright, Pretty Rich. Loosely Compressed. Stars from 7th to 12th Magnitude. John Sanford description: "M7 is much the larger [than M6], appearing as a fuzzy spot to the eye, against the background of the bright Milky Way. The diameter is nearly double that of the full Moon..." Like M6, cluster M7 is best enjoyed with large binoculars or a richest-field scope, and sparkles with yellow and orange stars.             Click for Deep-Sky Browser Page for Messier 7.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6494 - M23: Open Cluster in SAGITTARIUS Dreyer Summary (NGC): Cluster, Bright, Very Large, Pretty Rich, Little Compressed. Stars of 10th Magnitude. John Sanford description: "...a large open cluster lying to the west of the Small Cloud [part of M24 in Sagittarius]. It is made up of about 100 stars clustered in a 25 arcminute diameter with attractive curves of stars of similar brightness."             Click for Deep-Sky Browser Page for Messier 23. NGC 6531 - M21: Open Cluster in SAGITTARIUS Dreyer Summary (NGC): Cluster, Pretty Rich, Little Compressed. Stars from 9th to 12th Magnitude. John Sanford description: "...a cluster of bright stars northeast of the Trifid, with several dozen covering a diameter of 12 arcminutes." In binoculars or a richest-field scope, M20 may be seen in the same field of view as M21, which is conspicuous for its triangular asterism.             Click for Deep-Sky Browser Page for Messier 21.             Click here for Jaakko Saloranta's observation             and drawing. M24 - Milky Way Star Cloud in SAGITTARIUS A spectacular, detached segment of the Summer Milky Way, about a degree and a half in diameter, visible to the naked eye; formerly attributed to the small 5 arcminute open cluster NGC-6603, which Dreyer described as listed below. Now authorities attribute M24 NOT to the object described by Dreyer, but to the "Large" Star Cloud in Sagittarius, with NGC-6603 representing the "Small" Star Cloud within M24. This exceptionally dense region also contains a superb example of a Barnard dark nebula, B92.             Click for Deep-Sky Browser Page for Messier 24. NGC 6603: Small Milky Way Star Cloud in SAGITTARIUS Dreyer Summary (NGC): Remarkable Cluster, Very Rich and Compressed, Round, of 15th-Magnitude Milky Way Stars. This 5-arcminute concentration of somewhat brighter stars in the midst of M24 will be noticed at low powers and wide fields in an instrument of high-contrast performance, such as 11 X 80 binoculars or a 4 inch aperture richest-field scope. Apertures of ten inches or larger will resolve the faint stars of the association.             Click for Deep-Sky Browser Page for NGC-6603. NGC 6611 - M16: "Eagle" Open Cluster and Diffuse Nebula in SERPENS Dreyer Summary (NGC): Cluster, At Least 100 Large and Small Stars. The open cluster M16 is associated with an enveloping hydrogen cloud which records on film its dramatic red billowing curtains. Amateur telescopes of moderate aperture may reveal a trace of diffuse greenish-blue hydrogen-Beta nebulosity at the wavelength of 4861 angstroms with the help of a nebular-line filter, but the phenomenal ruddy patterns are mostly invisible to human eyesight. The bright stars of the cluster are nevertheless a majestic and soaring sight, and expand from a dozen visible members in a small scope to more than four dozen in large amateur instruments. Unfortunately amateur- sized scopes do not reveal in the eyepiece the details of the "columns" of gas and dust that are so memorable in the famous Hubble image.             Click for Deep-Sky Browser Page for Messier 16. NGC 6613 - M18: Open Cluster in SAGITTARIUS Dreyer Summary (NGC): Cluster, Poor, Very Little Compressed. A good choice for viewing by very small telescopes or large binoculars, M18 has about a dozen stars arranged in a wide and random pattern. It is easy to sweep from M18 to the spectacular M17, about a degree in right ascension to the west.             Click for Deep-Sky Browser Page for Messier 18.             Click here for Jaakko Saloranta's observation             and drawing. IC 4725 - M25: Open Cluster in SAGITARRIUS Dreyer Summary (Index Catalog): Cluster, Bright, Large, Little Compressed. A galactic cluster of about 50 stars brighter than 12th magnitude, containing the Cepheid variable star U Sagittarii. Notable color contrasts in the brightest stars may be visible with sufficient aperture.             Click for Deep-Sky Browser Page for Messier 25. IC 4756: Open Cluster in SERPENS Dreyer Summary (Index Catalog): Cluster, Compressed. John Sanford's description: "IC 4756 is a scattered open cluster at the north end of Serpens Cauda, most effectively seen in binoculars as there is little central condensation and the group is about a degree in diameter." Try an ultra-wide ocular with a richest-field telescope, or use your main instrument's finderscope to view this object.             Click for Deep-Sky Browser Page for Messier 25.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6694 - M26: Open Cluster in SCUTUM Dreyer Summary (NGC): Cluster, Considerably Large, Pretty Rich and Compressed. 12th to 15th Magnitude Stars. John Sanford description: "...not a strong object in an 8-inch (20-cm). It contains about 40 stars gathered into a 15 arcminute field." Binoculars or a richest-field scope may be able to show M11, also in the Scutum star cloud, in the same field of view.             Click for Deep-Sky Browser Page for Messier 26.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6705 - M11: "The Wild Duck" Open Cluster in SCUTUM Dreyer Summary (NGC): Remarkable. Cluster, Very Bright, Large. Irregularly Round, Rich. 9th Magnitude Star Among 11th Mag. Stars. Spotting this cluster with low power in a pair of 11 X 80 binoculars or in a richest-field scope providing the ultimate brightness and contrast, the viewer will see portrayed a wedge-shape of close stars against a fainter field of the Milky Way. Larger instruments and high powers will resolve many of the more than 600 stars of this group. The old NGC reference to a 9th magnitude star (" *9, st 11...'") in Dreyer's code may signify the multiple star J 107, whose A and B components are separated 5.8" at 8 and 12.4 magnitude, or slightly more distant Struve 2391, a wide 38" double of 6.5 and 9.8 magnitude stars, some 3 or 4 arcminutes from M11 to the southeast. 19th century observer Admiral Smyth gave this object its nickname, writing that it looked like a flock of wild ducks in flight.             Click for Deep-Sky Browser Page for Messier 11. NGC 6791: Open Cluster in LYRA Dreyer Summary (NGC): Very Faint Though large in diameter, this rich galactic cluster of nearly 400 dim stars is faint in small, inefficient telescopes. Larger instruments will reveal some resolution into stars, including members as bright as 11th magnitude, dimming to 13th magnitude. It may be found in a fairly wide field with the fourth-magnitude star Theta Lyrae.             Click for Deep-Sky Browser Page for NGC-6791. Collinder 339: "Brocchi's Cluster" - Cluster (or Asterism) in VULPECULA John Sanford description: "Vulpecula contains the charming 'Coathanger' asterism, officially known as Brocchi's Cluster. This group of 10 stars is visible to the naked eye as a small fuzzy spot and has no NGC designation. The slightest optical aid will show an almost perfectly straight line of six stars with four more making a hook protruding from the center of the line. It looks exactly like a small upside-down coathanger." In narrow fields of view typical of beginners' refractor telescopes, the shape of the asterism is lost, so use only a richest-field instrument with wide ocular design, a finderscope, or binoculars.             Click for Deep-Sky Browser Page for Collinder 339. NGC 6819: Open Cluster in CYGNUS Dreyer Summary (NGC): Cluster, Very Large and Rich, With Stars From 11th to 14th Magnitudes. John Sanford description: "There are 28 open clusters in Cygnus, and 11 planetaries, but no globular clusters and no extragalactic systems, due to the Milky Way obscuration. NGC 6819 is a rich galactic cluster, containing 150 stars from 11th magnitude and fainter. It is almost exactly 5 degrees south of Delta, and best approached with telescopic apertures of 8 inches (20 cm) and above."             Click for Deep-Sky Browser Page for NGC-6819.             Click here for Jaakko Saloranta's observation             and drawing. Harvard 20, Cr 408, or OCL 116: Open Cluster in SAGITTA This small constellation contains few telescopic objects, and is perused most often for the well-known globular cluster M71. Harvard 20 is an open cluster worth identifying when observing this region. Barely discernible in a 2 - 3 inch scope, it will resolve into one to two dozen stars with larger apertures.             Click for Deep-Sky Browser Page for Harvard 20.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6913 - M29: Open Cluster in CYGNUS Dreyer Summary (NGC): Cluster, Poor, Little Compressed. Large and Small [bright and faint] Stars. A homely arrangement of a dozen fairly bright stars of nearly 8th magnitude, M29 might appear more brilliant were it not for the heavy interstellar absorbing matter present. It is easily found just about 2 degrees to the south of the central star of the Cygnus cross, Gamma Cygni. Do not confuse M29 with NGC-6910, closer to Gamma Cygni and roughly opposite M29.             Click for Deep-Sky Browser Page for Messier 29.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6939: Open Cluster in CEPHEUS Dreyer Summary (NGC): Cluster, Pretty Large and Rich, Pretty Compressed Middle, Stars of 11th to 16th Magnitude. John Sanford description: "NGC 6939 is a rich but rather faint galactic cluster situated on the edge of our Galaxy's obscuration. We know this because only 38 arcminutes southeast (less than a low-power field) is NGC 6946, a nearby low-surface-brightness Sc galaxy." The galaxy's integrated visual magnitude is about 8.8, and thus the cluster appears brighter in small apertures that may not resolve its stellar components.             Click for Deep-Sky Browser Page for NGC-6939.             Click here for Jaakko Saloranta's observation             and drawing. NGC 6994 - M73: Asterism in AQUARIUS Dreyer Summary (NGC): Cluster, Extremely Poor, Very Little Compressed, No Nebulosity. A group of only 4 stars of 10th to 12th magnitude, possibly not a related cluster, that Messier mistook for a nebulous patch. In the smallest instruments at low power, it may also fool modern viewers; high magnification reveals the stellar components.             Click for Deep-Sky Browser Page for Messier 73.             Click here for Jaakko Saloranta's drawing             with 3" refractor at 130x. NGC 7092 - M39: Open Cluster in CYGNUS Dreyer Summary (NGC): Cluster, Very Large, Very Poor, Very Little Compressed. 7th to 10th Magnitude Stars. A larger but equally mundane open cluster in comparison to Cygnus' other such Messier object, M29. 19th century observers like Webb found it a "grand" sight, but they did not have the benefit of modern nebular filters and wide-field oculars for the appreciation of the stunning nebulae in the region. More interesting in binoculars or small scopes than in large ones.             Click for Deep-Sky Browser Page for Messier 39.             Click here for Jaakko Saloranta's observation             and drawing. NGC 7209: Open Cluster in LACERTA Dreyer Summary (NGC): Cluster, Large, Considerably Rich and Pretty Compressed, With Stars from 9th to 12th Magnitudes. The constellation of the Lizard contains relatively few bright pattern stars, but has several open clusters and a fine grouping of double stars. John Sanford described NGC 7209 as "a fairly concentrated galactic cluster...made up of several dozen stars from 8th to 11th-magnitude."             Click for Deep-Sky Browser Page for NGC-7209.             Click here for Jaakko Saloranta's observation             and drawing. NGC 7243: Open Cluster in LACERTA Dreyer Summary (NGC): Cluster, Large, Poor (sparse), Little Compressed, Stars Very Large [i. e. bright]. John Sanford description: "NGC 7243 is another galactic cluster [in Lacerta] of about 40 stars, which includes the triple Struve 2890 consisting of a pair of magnitude 8.5 stars separated by 9.4 arcseconds, and another of magnitude 9.5 some 73 arcseconds away."             Click for Deep-Sky Browser Page for NGC-7243.             Click here for Jaakko Saloranta's observation             and drawing. NGC 7654 - M52: Open Cluster in CASSIOPEIA Dreyer Summary (NGC): Cluster, Large, Rich, Much Compressed in the Middle, Round. Stars from 9th to 13th Magnitude. Like other Messier open clusters M37 and M41, a bright red star is visible in this object's field; yet it is not an actual member of the group of pale faint stars, which are unresolved in the smallest scopes. Larger apertures will do justice to the sprinkling of nearly 100 visible stars.             Click for Deep-Sky Browser Page for Messier 52.             Click here for Jaakko Saloranta's observation             and drawing. (c) 1996-2007 Stephen R. Waldee - All Rights Reserved. Quotes from "Observing the Constellations" by J. Sanford, Fireside/Simon & Schuster, 1989, by permission. Historical Materials (NGC-Index Catalog, etc.) from UC/Lick Observatory. "Deep Sky Browser" Pages © 1998-2004 Mikkel Steine, www.Messier45.com (not affiliated with this website)   SELECTED REFERENCES Articles and Books: Data Drawn from OBSERVING THE CONSTELLATIONS by John Sanford, 1989, Fireside/Simon & Schuster, and quoted by permission. NGC 2000.0, edited by Roger Sinott: 1988, Sky Publishing. OBSERVING HANDBOOK AND CATALOGUE OF DEEP-SKY OBJECTS by Christian B. Luginbuhl and Brian Skiff; 1989, Cambridge University Press. URANOMETRIA 2000.0 by Tirion, Rappaport, Lovi; 1987-89, Willman-Bell. THE BEDFORD CATALOGUE by Admiral William H. Smith; 1844; reprinted 1986, Willman-Bell. CELESTIAL OBJECTS FOR COMMON TELESCOPES, Vol. II, by Rev. T. W. Webb; 1859; reprinted 1917 and 1962, Dover Publishing. Images: Most of the thumbnail images above were prepared by the author using the Palomar Observatory Sky Survey I plates, obtained from the Digital Sky Survey, available on the web:        http://archive.stsci.edu/cgi-bin/dss_form Acknowledgments are required for use of the images, and may be found at:        http://archive.stsci.edu/dss/acknowledging.html Other images were prepared from material in the Waldee- Wood Astronomical Software program EYEPIECE. Links: Deep-Sky Browser Pages:        www.messier45.com. Be sure to see also Jaakko Saloranta's webpages of the        50 Best Open Clusters and Asterisms        of the Northern Hemisphere and        Visual Impressions of Bright Open Clusters        in the Milky Way. All trademarks are copyright (c) their original copyright holders. This article Copyright (c) 1996-2008 Stephen R. Waldee - All Rights Reserved.   Press BACK key, or click for the Main Object Menu, Or the Full Moon Essay Menu or the Eyepiece Page. 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