SEPTEMBER

VVandering Through Lacerta, the Lizard

No region in the heavens is barren," Scotty wrote. "No constellation is fruitless tor the observer. Even a lifetime of exploring the celestial display cannot exhaust the surprises that dance so beautifully before the amateur astronomer." His words _ring true because some regions of sky remain frequently overlooked by backyard observers. Consider Lacerta, the Lizard. In the September 1972 Deep-Sky Wonders, Scotty told how James P. Brown of Kingsport, Tennessee, pointed out to him that, for many years, the column had curiously omitted that constellation. Tucked between Cygnus and Andromeda, Lacerta extends almost a full hour in right ascension and about 20° in declination, but its brightest star shines at a dim 4th magnitude. "Inconspicuous as Lacerta, the Lizard, may be," Scotty proffered, "it nevertheless offers some good open clusters for September viewing." / \ September evenings, the small constellation Lacerta crawls high overhead. This celestial lizard was created in 1687 by Johann Hevelius to fill the void between Cygnus and Andromeda. Some eight years earlier, the French astronomer Augustin Royer used the handful of naked-eye stars in this area to portray a scepter and hand of justice commemorating King Louis XIV of France. And, almost a century after Hevelius’s figure, the German Johann Bode used ’hese same stars to form Frederici Honores as a tribute to his sovereign Frederick •be Great. But just as the rule of a monarch is temporary, so too was the accep-^lance of these asterisms, and today only the lowly lizard occupies this space.

Lacerta is a weak little constellation tucked alongside the galactic equator and ^niUcb overshadowed by its vivid neighbors Cygnus and Cassiopeia. Because ^acerta’s naked-eye stars are all inconspicuous, they provide an opportunity for observers to test their skills at finding their way far from bright guidepost stars. Its ghtest star, Alpha (a) Lacertae, is only magnitude 3.8, so from a light-polluted ^an location the celestial lizard may be a bit difficult to find. Because of a lack tel ®^u*d^{e stars t0} help point the way, this area is a good place for the novice ^Sc°pe user to practice hunting with a finder.

There is a good reason why amateurs should get familiar with Lacerta <jj 1910 three novae have blazed out in this area, and more will certainly _Co^nCc Because there are no stars brighter than 4th magnitude to distract the obse ^C‘ a relatively faint interloper should be evident.                               ^Ver’

Though it has no spectacular deep-sky objects, it does contain several br „k clusters that can be reached with modest instruments. As many observers kn^ areas of the sky that appear empty to the naked eye often hold interesting _g0o*’ ies for a small telescope. Sentiment often drives me to take a look at two mult, pic stars in Lacerta that I learned of in my youth, while surveying the sky with copy of the venerable Norton’s Star Atlas. Struve 2894 consists of a pair of 6 1 and 8.3-magnitude stars separated by 16".This puts them well within the grasp _Of a 2-inch telescope. The second, 8 Lacertae, is a pair of 5.7- and 6.5-magnitude stars about 22" apart. Two other stars of 9th and 10th magnitude lie 82" and 49" from the primary, respectively, and may be part of the same physical system.

NGC 7243 is the only cluster in Lacerta mentioned in the classic observing guides by William H. Smyth and Thomas W. Webb (the 1881 revision of Smyth’s Cycle of Celestial Objects by George F. Chambers added another open cluster NGC 7209). Smyth notes that the surrounding area is very rich, especially to the north of the group. To find NGC 7243 look for a small keystone of stars, including Alpha, Beta (p), and 4 Lacertae, which should fit within the field of any finder. NGC 7243 is along the southwest edge of this keystone, about 2'Z° west and a

Figure 9.1

The open cluster NCC 7243 is a fine sight in large binoculars and small telescopes.

little south of Alpha. It is a splashy coarse star grouping about 20' across (Figt*^re 9.1) with a total magnitude of about 7.5, making it a good object for deep-sky binoculars with 80-mm objectives. Sky Catalogue 2000.0, however, lists the group as having a total magnitude of 6.4, which might make it visible to the naked eye under the best observing conditions.

The cluster stands out especially well from the stellar background when I ^st°P my 4-inch Clark refractor down to 1.8 inches. According to Revue des constell°

■f

I _y by R- Sagot and Jean Texereau, NGC 7243 in a 4-inch at about 5()x is a rich _gU]ar cluster of many stars between 9th and 1 lth-magnitude. The number of "' "' increases from about 15 in a 2-inch to 60 in an 8-inch. I found no definite ^S' ^r • in a 12-inch recently, but counted at least 80 stars within a !4° area. Look for ide double star at the cluster’s center, particularly if you have a 6-inch or larger *' cope. Try using different magnifications on this cluster. Often certain features f object are apparent only at specific magnifications. This is also an interesting ⁰ . ₁₁₀ try sketching. First rack your eyepiece out of focus to the point where nlv the brightest stars are seen. Add these and continue the process until sharp focus reveals the faintest stars.

About 4° southwest of NGC 7243 is NGC 7209. Its rather scattered bright stars figure 9.2) cover an area roughly 20' in diameter and are visible in my 2-inch finder Try star-hopping from the first cluster to the second one by following the small ^^emicircle of naked-eye stars 4,5, and 2 Lacertae. NGC 7209 is slightly smaller and ^ainter than NGC 7243. It stands out nicely from thc Milky Way background of ^^ar dust, lying within a rough pentagon of five brighter stars that can all be seen

the field _of _vj_ew ;_s y₄° _or |_arg_er. As many of the cluster's stars are between 9th and 10th magnitude, NGC 7209 is excellent in my 4-inch refractor. It _S|_1Q more than 50 stars in a 6-inch. Some amateurs call this object triangular but I wonder whether they have been looking at NGC 7243 instead. Read-who record their impressions of this cluster should note instrument size m nification. and sky condition. Look for an orange 6th-magnitude star 15' north east of NGC 7209.

For those who want a challenge, the small open cluster NGC 7296 is 40'

^3St of 4th-magnitude Beta Lacertae. This lOth-magnitude cluster lies on a rich back ground, which might be a hindrance since NGC 7296 is only 4' in diameter At 20x my 4-inch Clark refractor had a difficult time with this object. Glare from 4th-magnitude Beta and the rich Milky Way background made the cluster hard to pick up. Yet NGC 7296 can be found with a little patience. By increasing the refractor’s magnification to 80x, NGC 7296 was easily found, and the view at 150x was even better. Sweeping for the cluster at these higher magnifications is made easier by bright Beta Lacertae — if you get lost, return to the star and begin the search again. After examining the cluster at 150x, try sweeping nearby, or just letting the stars drift. This is an excellent way to discover many curious sights never seen during low-power sweeps.

Near the northern border of Lacerta, just west of the halfway point on a line between Beta Lacertae and Epsilon (e) Cephei, is a rather difficult open cluster. NGC 7245. It is only 5' across and of magnitude 11.5. NGC 7245 can be identified in 20 x 65 binoculars but is much more satisfactory in a 10-inch telescope. Recently, I could not locate it with a 5-inch at 20x, but when I switched to my 4-inch refractor at lOOx it was clearly seen. There is a triangle of three stars between 8th and 10th magnitude here. More than a dozen stars can be seen with a 12-inch telescope, but perhaps only half this many are within the grasp of an 8-inch instrument.

Somewhat richer than NGC 7245 is the open cluster IC 1434. Generally, objects in the Index Catalogue supplement to the NGC are faint and hard to locate, but the cluster IC 1434 is easily found. Continuing on a straight line from 9 Lacertae to Beta Lacertae for about the same distance that separates these stars will put you in the cluster’s vicinity. IC 1434 is an 8' grouping of perhaps 30 stars. Of 10th magnitude, it is a dull little cluster, but one that is improved considerably by running up to 150x or 200x and using averted vision.

As viewed from Connecticut with a 6-inch. IC 1434 appears as a compact ball of faint stars, about 6' to 8' in diameter; I have the feeling that this object might be a very pretty sight in a 16-inch telescope.

The group lacks solidarity and appears as if several clusters have been jumble^ together.The English amateur Guy Hurst, writing in the Webb Society Deep-Sky Observer’s Handbook, Vol. 3, Open and Globular Clusters, mentions that the cluster seems backed by "considerable haze” (by the way, this handbook incorrectly states the cluster is in Cygnus). The surrounding sky is quite rich, and 1 recommend that you spend some time just sweeping the nearby area.

a cluster missing from most catalogs and charts is NGC 7394. Canadian rver Pat Brennan describes it as "a coarse grouping about 10' by 3' across _{h a} brisht star at the southeast end." In addition to the bright star at its south-'^V8 -nd there are about 10 fainter ones. Since the field is not particularly rich, the ^C -r can be easily recognized! When John Herschel swept up this grouping in ^C 79 he noted in his record book that the measured position referred to “a dou-. star the last of a poor cluster of about a dozen stars.”

^NJore challenging than any of these clusters is the 12th-magnitude planetary _ebula IC 5217. It is located just slightly northeast of center in the stellar keystone

Figure 9.3

The challenging 12th-magnitude planetary nebula IC 5217 in Lacerta is roughly 8,000 light-years distant.

Quintet (see Sky & Telescope for Marell 1977. page 170). The latter is a group ₀ much fainter galaxies, very difficult for amateurs, lying 30' to the south-southw °

Cruising Through Cygnus

"If one constellation dominates September evening skies," Scotty said, "it is the one known to the ancients as Cygnus, the Swan, and to less imaginative moderns as the Northern Cross." Regardless of how we see the constellation, one thing j_s f_Or sure: few of us can resist sweeping our binoculars and rich-field telescopes across the dark and bright expanses of Milky Way that flow through Cygnus like a snow-banked river at night. A main attraction of this constellation is its many open clusters, especially the bright Messier objects M29 and M39. But Cygnus has much more to offer. In fact, Cygnus is one constellation that has it all: double stars, variables, dark nebulae, gaseous nebulae, galaxies, planetary nebulae, and even a supernova remnant — and, of course, plenty of telescopic challenges.

Deep-sky observers are discovering Cygnus. Does this sound peculiar? After all, the constellation is a landmark of the late-summer sky and is awash with bright lanes of the Milky Way. Even a naked-eye view suggests that Cygnus should be a deep-sky wonderland. But only recently have amateurs pursued the individual delights that the constellation has to offer.

Most deep-sky objects in Cygnus have been overlooked because they were never mentioned by Smyth or Webb in their observing guides. Early observers paid surprisingly little heed to these objects. Smyth mentions only M29 and M39 in his famous (but now scarce) Cycle of Celestial Objects (written in 1844). Webb is almost as brief in his Celestial Objects for Common Telescopes (first written in 1859). But he says of Cygnus: “I had at one time projected a survey of the wonders of this region with a sweeping power; but want of leisure, an unsuitable mounting, and the astonishing profusion of magnificence, combined to render a task hopeless for me which, I trust, may be carried through by some future observer.”

In addition to the two open star clusters Messier cataloged in Cygnus. Smyth also called attention to the planetary nebula NGC 6826. Webb did slightly better by adding a wisp of the Veil Nebula near 52 Cygni, three clusters, and two interesting star fields (one containing the cluster NGC 6871, which he did not mention per se).

Both authors went on at length about the variable and multiple stars in the constellation, but it seems they did not spend much time at the eyepiece cxpl°^r' ing Cygnus themselves. If they had, certainly they would have written about some of the splashy open clusters scattered through this corner of our galaxy-

Later authors followed in the footsteps of those before them, and amateurs weren't directed to the lesser-known sights in Cygnus until the late 1970s when Burnham's Celestial Handbook became widely available. This work includes j_eep-^sky objects in the Swan, and there are even more plotted on Tirion's Sky _Ali_aS 2000.0.

Today's amateurs, however, are not content to use just the popular guides, frequently they roam the sky on their own, and I regularly receive mail from bservers who have “discovered” a star cluster. Most of these objects are listed in the /Vetv General Catalogue of Nebulae and Clusters of Stars. When I write back saying their cluster is in the NGC they reply,“If it’s known, why isn't it plot-_ted on the star atlases?" The answer is that the charts include only a representative sample of deep-sky objects, and most of them have been selected from the observing guides mentioned. The Tirion charts, for example, show some 2,500 deep-sky objects, which is less than one quarter of those listed in the NGC and its Index Catalogue (IC) supplement.

A superficial inspection of these catalogs suggests that only about half of the objects listed in Cygnus are plotted on the Tirion atlas. Alister Ling of Montreal has been sweeping Cygnus in search of objects not usually mentioned in observing guides. Writing in the newsletter Betelgeuse, he says that in crowded star fields he looks for hazy blobs in his viewfinder that often turn out to be magnificent clusters when seen with the main telescope. This search technique is especially useful for locating large open clusters. Ling mentions three clusters, NGC 6910.6997, and 6871, that have never been described in this column. All are plotted on Sky Atlas 2000.0, so why not hunt them down yourself?

Ling has also been using a UHC filter on his 12-inch Dobsonian at 56x.The North America Nebula (NGC 7000) “jumped out” and detail never before visible was evident. Furthermore, while casually sweeping nearby he stumbled upon the elusive Pelican Nebula (IC 5070). On another night he viewed the

Figure 9.4

The glorious North America Nebula in Cygnus may be illuminated by an inconspicuous star that is obscured by dark clouds near the nebula's "Atlantic coast." The hard-to-spot Pelican Nebula flies alongside to the west.

section of the emission nebula IC 1318 cast of Gamma (y) Cygni, the star of the Northern Cross. It appeared as a “huge sprawling region of losity split in two.”

One of the most controversial objects among amateur observers, the Nn I America Nebula (Figure 9.4) is familiar from photographs as a large diffuse o/¹¹' about 3° east and 1° south of Deneb. There has been remarkable diversity * opinion on how small a telescope can show this object visually. Some argue that thc nebula cannot be observed readily without photography, but thc region is rich that it is well worth sweeping with anything from binoculars to large tele scopes. Early telescopic observers all missed NGC 7000 because of its large size (relative to the fields of their instruments) despite its brightness. Only in the last generation or two, with the rise of rich-field designs, has the nebula become gen erally accessible to telescopes.

If observing conditions are very good, and you know what size and shape to expect, the North America Nebula can be made out easily with the naked eye An opera glass makes it more apparent, but this is not true when more powerful binoculars are used. When I was in grade school 1 had a small folding opera glass, bought for a dollar at a carnival, and it showed the nebula! Actually, NGC 7000 is difficult to see in most telescopes. With a 5-inch Moonwatch Apogee telescope you should know beforehand what it looks like, and the nebula is downright challenging in a 6-inch f/4. However, a few years ago it was brilliant when I saw it in Edgar Everhart's 11.4-inch Wright telescope, which was then located in

Connecticut.

In northern Cygnus there is a sparse cluster that may have been spared the indignity of a “nonexistent” label because it carries the protection of a Messier number. The open cluster M39 has a distinct triangular shape. The group is 32' in diameter and 4.6 magnitude. Hence it’s within reach of the naked eye. Discovery is credited to the French observer Jean-Baptiste Le Gentil in 1750, who described it as “very dim” but visible without a telescope. In a small, low-power telescope M39 shows as a nice sparkling cluster. Smyth called it a “splashy galaxy field of stars.” Recent printings of Webb’s observing guide call M39 a "grand open cluster,” but the original never mentioned the group. It appears io have been added to the guide during a revision of the sixth edition by Thomas E-Espin in 1917.

Lc Gentil refers to thc triangular shape of M39 but orients it differently than most observers today see it. It is not clear to me, however, if his observation of the shape was made with the naked eye. Will someone try examining M39 with a range of instruments (don't forget binoculars and thc unaided eye)?

Several years ago, while observing from the Southern California desert-glimpsed a dark streak running about 5° east-southeastward from M39. 1 h^{ere |S} no doubt about a vacancy some 6' across on the east side of M39. From it ^{a na} row, dark lane can be traced eastward with difficulty for perhaps 2/ ^unt*' ¹ merges with a much wider and pronounced stream that leads to the Cocoon bula. IC 5146. The obvious dark lane is Barnard 168, which is shown without label on Uranometria 2000.0 charts.

Catalogue

a

⁸ The detection of dark nebulosity depends on many factors. I lean toward using -focus instruments because my experience has shown that they tend to scat-^less I'Cht ^ancl P^rov>de ^a higher-contrast image than do rich-field telescopes. I *^e , had some dramatic views of dark objects with my old 10-inch f/8.5 ^⁸ Etonian reflector and the 12-inch f/17 Porter turret telescope in Springfield, ■708) is NGC 6819. I found this grouping early in my high-school days. It was barely detectable in my homemade 40x 1-inch refractor. According to information in Vol. 2 of Sky 2000.0. NGC 6819 is whopping 3'/2 billion years old. Thc cluster is 7th magnitude, 5' across, and contains perhaps 20 stars of magnitude 12 and fainter. The Webb Society handbook on clusters mentions several reports of nebulosity involved with the group.

Have others seen this?

In contrast with the age of NGC 6819 is M29, estimated to be only 10 million years old (Figure 9.5). While the former is nearly as old as our solar system, the latter formed not long before humans appeared on Earth. M29 is slightly larger •ban NGC 6819 and shines with a total light equal to that of a 6.6-magnitude star, doubt thc cluster can be picked out from the rich Milky Way background with *be naked eye.

NGC 6866 is about thc same size as M29 and a magnitude fainter. Catalogs list stars here. 1 have no reports of NGC 6866’s appearance in a 16-inch or larger telescope, but a 6-inch captures a nebulous glow that is probably caused by unresolved stars. In a 10-inch at 150x, the field of view is filled with sparkling starry ^exc>tement.

NGC 6894 is a planetary nebula in Cygnus, which photographs show as a fa-diamond 44" in diameter.Though it has been cataloged as magnitude I4.4 . ^1,1 teurs can see it, and Agnes Wolfe writes that it seems brighter than the cat 7 J values. James Corn of Phoenix, Arizona, observed it on July 16,1952, as m ' tude 12 and large.                                                            ^a®ⁿ*'

Another object this month is the planetary nebula NGC 6826 in Cy_gnu Although not well known today, I found a reference to it while looking f_Or ..^S' lier mention of the Veil Nebula in an 1856 edition of Elijah Burritt’s Geo«_r„ of the Heavens. With a total light equal to a star of magnitude 8.8, in modest apertures this planetary shows a fine greenish disk about 25" across.

NGC 6826 is plotted in Norton’s with the Herschel number 73⁴. Since the pl_an etary’s 1 lth-magnitude central star was easily seen by William and John Herschel, they considered this nebula a transition object between regular p]_an etaries (whose central stars were too faint to be seen) and stars involved in diffuse nebulae. At 300x, a 10-inch reflector I had in Kansas showed NGC 6826 to have uniform light across its center. The planetary takes magnification well and is a fine object for even small apertures.

Also try finding the spiral galaxy NGC 6946 in extreme northern Cygnus. This is only 10° from the plane of our Milky Way, where it is unusual to find galaxies since the interstellar dust concentrated there obscures the light from these distant objects. Though listed as about 9' x 7' in size, this galaxy seems even less round to me. Despite the glittering foreground star field, NGC 6946 stands out well.

Unveiling the Veil

The most popular deep-sky object in Cygnus today is the Veil Nebula, though it is difficult to observe. This visually fragmented bubble of glowing gas is so large (hat most telescopes cannot contain it in one field. The challenge, of course, is seeing it at all. Over the years amateurs provided Scotty with conflicting reports as to its visibility. "While some have missed it even with large telescopes," he wrote, "Burnham has seen it with binoculars. My opinion is that the Veil is more a test of observing skill than optical parameters." Indeed, Scotty witnessed the Veil Nebula evolve from something that amateurs knew only on photographs to one they routinely studied with small telescopes. Conversations at star parties, he said, once swirled around how to view such "difficult" objects. Today, those conversations are part of amateur astronomical history, an intriguing fireside tale to share with novices, and the Veil is yet another of amateur astronomy's ever-growing list of "ex-test" objects.

The most famous celestial sights have been passed down to us throughout the centuries. The Orion Nebula is one. Another is the Andromeda Galaxy-M31, first noted in writing by the Persian al-Sufl in A.D. 964. It seems unlike that any observing guide published after Messier’s 1764 discovery of M27 fails

tion this beautiful planetary nebula in Vulpecula, and amateurs teach each nief¹¹ .  ...

■her to ^{,intl ll}‘

⁰  || things considered, amateurs might think that the deep-sky objects sought

at today’s star parties have been scrutinized and described over and over

^1,111. _{hv n}ast observers. However, this is not the case. There are some objects 'igtill* *

¹'] ich in a sense, belong to the modern amateur.They deserve caretui attention, ' published visual descriptions are surprisingly few.

f°One such object is the Veil Nebula in Cygnus (Figure 9.6), a broken bubble of luminous gas some 2° in diameter. Although ignored by generations of telescope users in the last 30 years the Veil has progressed from a difficult test object to a

Figure 9.6

The Veil Nebula in Cygnus is believed to be the remnant of a supernova explosion that occurred at least 15,000 years ago. The filamentary remains are expanding at nearly 30 miles per second.

reasonable target for anything from binoculars to the largest amateur telescopes, h is an excellent nebula for training the eye, perhaps the most important observ-^lng “accessory,” to help us get the most out of the telescope we are using.

Astronomers believe the Veil comprises the remains of an ancient supernova. When I was young the Veil was usually listed as a planetary nebula, since the ^c°ncept of supernovae and their remnants didn’t come until the 1930s when I ^Uas ’ⁿ college. Back then the Veil was considered a unique object. Today, how-^ever, we know of several others like it, including S147 in Taurus.

William Herschel discovered the brighter parts of the nebula as he swept the ^Sky with his 18%-inch speculum-metal reflector in 1784. He included the east and ¹ sections of the loop with his class V objects (very large nebulae). In °rr_on;_v Star Atlas the westerly section carries his designation 15⁵, and it also ^ears the name NGC 6960.

The 4th-magnitude double star 52 Cygni appears to be involved with NGCftor but is actually a foreground object not related to the nebula. Incidentally, th_e mistakenly identifies the star as Kappa Cygni, and other catalogs have Somet' copied the error. Even in small telescopes, 52 Cygni is an excellent double-orange and blue components, magnitudes 4.5 and 9.5, are separated by 6'/_;" ’ '^tS

The eastern loop of the Veil is NGC 6992-95 (14^s in Norton’s). Like the w_est part, it is a strip of sculptured light about 1° long. Between the outer parts of loop are several fainter wisps of nebulosity, which show well in long-exposure ph^ tographs.Thc larger triangular piece, discovered photographically, carries nodesi nation number. Just to its east is a smaller patch of nebulosity, NGC 6979. Herschel again was its discoverer, and placed it with his class II objects (faint nebulae)

Why has the Veil Nebula been overlooked for so long? It certainly could have been seen with the reflectors and comet-seeking refractors trained on the sky back in the 19th century. I suspect there were two reasons for omitting the Veil from earlier observing guides. First, Herschel called NGC 6960 only “pretty bright” and NGC 6992-95 “very faint,” although the latter is in reality the more easily visible. Smyth may have been more responsible for diverting subsequent amateur attention from the Veil. In his Cycle of Celestial Objects he mentions only NGC 6960, and then only as an afterthought in his section on 52 Cygni. He unenthusiastically noted that the field of view in his 6-inch refractor required “considerable attention” before he was able to make out any of the nebulosity.

Other popular observing guides by T. W. Webb and Charles Barns make no mention of the Veil, although by the time of the publication of Bams’s work in the 1920s, photography had revealed the splendor of the nebula's twisted filaments.

Tn the 1940s and 50s, amateurs considered the Veil a test object. Often my mail contained bitter reports of failure to see the Veil’s faint glow. However, today it is more typical to receive detailed descriptions from confident observers. My own experience has followed a similar pattern, which I attribute to the growing education of the eye, and to knowing the Veil can be seen visually.

Richard Wilds of Topeka, Kansas, has glimpsed the three brightest sections of the Veil (those with NGC numbers) with a 2-inch refractor. In his Celestial Handbook, Burnham mentions seeing NGC 6992-95 in large binoculars. Indeed, both the east and west arms of the loop are easy in my 20 x 125 Japanese military binoculars. In a 12-inch f/5 telescope the Veil Nebula in Cygnus is beautiful-and so bright that one notes it even when sweeping. But in a 5-inch f/5 the Veil is visible only with difficulty to keen eyes. Why is this so, when the surface bright" ness of extended objects depends on f-ratio rather than on aperture?

'The seeming contradiction is removed when the eye is considered along ^w>* the optics of the telescope. Physiologists have shown that the eye can discern spot 6° in apparent diameter that is only 6 percent brighter than the backgroun • while a 2° spot must be 11 percent above background. Remember, a galaxy^vvl a diameter of 3' when magnified 100 times has an apparent diameter ol 5.0 •

Hence, the greater magnification usually obtained with larger telescope (because of their longer focal lengths) may help to reveal nebulae near the ^V1S

threshold- This is contrary to popular recommendations, but 1 have succcss-⁸ iiv used high powers, especially on planetaries. Of course, when magnification

• • increased the surface brightness rapidly becomes less. Hence one should not

• *  high powers on objects that already have large angular diameters. ^US^tv"most spectacular view of the Veil was in the mid-1960s from Connecticut,

here at best, the skies are usually undistinguished. I was sweeping with Edgar gverhart’s 12-inch Wright reflector when the giant bubble-like nebula was

■ Red up. The Wright reflector has a 12-inch primary mirror and an ll/2-inch ^rector plate. This visual instrument works at f/4, and is actually a variation of (he Schmidt camera. Everhart, who discovered Comet 1964h, constructed this telescope especially for comet seeking, and mounted it atop a 35-foot tower to obtain a clear view of the horizon. With an Erfle eyepiece giving about 50x, it provided some unusual views of deep-sky objects.

While discussing the instrument’s capabilities, we wondered if it would show the two arcs of the Veil Nebula in Cygnus. We tried to find NGC 6960 (the western segment) first, because the 4th-magnitude star 52 Cygni lies on the middle of the arc. Since Everhart’s telescope is an altazimuth (for comet sweeping), he pointed the instrument by sighting with the 3x finder while I watched through the main eyepiece.

As we swept over 52 Cygni, the nebula was seen without straining. It appeared to stream across the field. In the Wright telescope the nebulosity did not look as it does in photographs, but this was still one of the most fascinating sights I have seen in a decade or more.

Later we tried for NGC 6992-5 (the eastern arc); there are no bright stars near, so we had to proceed carefully. Sweeping casually, we might have missed this object, but once it was definitely in the field it could be seen easily. Though not as bright as NGC 6960, it was sharply defined; the structure was less evident than in the companion nebula. In all.it was about as noticeable as the faint outer parts of the Orion Nebula.

New nebula filters have apparently helped many locate the Veil. A typical sighting is that by John Bartels. He set up a 414-inch f/8 surplus telephoto lens with ^a 32-mm Plossl eyepiece and Henzl 300 nebula filter at the light-polluted airfield oi Travis Air Force Base. NGC 6992-5 could be seen without the filter, but was easier with it. NGC 6960 was located only with the filter, but after knowing where and what to look for he was able to glimpse this western loop without it.

How times have changed. Now I often receive reports of the Veil being seen ^ln binoculars. Even novice observers have seen it well enough to record the east-^ern portion of this giant 2°-diameter broken loop as brighter than the western ^s,rand passing near 52 Cygni. At the 1984 Texas Star Party, Lee Cain with his 17-*^nch Dobsonian binoculars saw the Veil so bright that he almost “feared it would ?*^ln my dark adaptation.” Bryce Heartwell of Alberta, Canada, considers the ^ei “totally beyond description” as seen with his 17-inch reflector. When he ^added a Lumicon UHC filter to the system, “the Veil showed as much detail as ^Photographs.”

the altitude motion is provided by the binoculars’ built-in trunions. Thoi

mo

With the crescent Moon in the sky I selected the portion of the Veil nearest Epsilon Cygni as a difficult test. Yet the binoculars promptly revealed these

wisps of nebulosity, and with averted vision 1 could even glimpse structure.

1 have also heard from experienced observers that the Veil can be seen with the naked eye through a UHC nebula filter. This is amazing when you consider that only a few years ago most amateurs thought of the Veil as one of the sky's great telescopic challenges. Dozens of observers have written me enthusiastic letters about the Veil’s appearance in telescopes equipped with UHC filters. Both the eastern (NGC 6992-95) and western (NGC 6960) sections of the nebula show delicate filamentary structure.

The following report from Joanne Konst of Kenton, Ohio, will be of interest to everyone who plies the heavens through city lights. Her house lies just two blocks from the center of town on a corner lot bathed in the glow of street lights. From her second-floor balcony she scans the sky with a 10.1-inch Dobsonian reflector and a battery of Lumicon filters. “The Veil Nebula in Cygnus reveals many features,” she writes. “NGC 6960 on the western edge was difficult without the filter due to glare from 4th-magnitude 52 Cygni. The eastern section of the loop. NGC 6992, is very detailed. While I can see it without a filter, using one enhances the view and brings out faint details. The edges look like ragged cotton, and 1 can see many delicate filaments. NGC 6979, as well as several other patches within the confines of the loop, are visible with a filter.” Perhaps her report will inspire others to try their telescopes from less-than-pcrfect observing locations.

The Mystery of NGC 6811

Scotty claimed that in spite of the electronic revolution sweeping amateur astronomy, we should remember that the eye itself performs extensive image processing. As an example, he introduced us to the open cluster NGC 6811, a small group of stars in Cygnus's northwest wing. At a glance, the cluster appears rather innocuous, containing about 70 stars and shining near 7th magnitude. Indeed, when Scotty looked at it in his youth he recalled it to be "an unimpressive, nondescript group-But a letter he received in the mid-1980s from amateur observer Tommy Christensen not only changed his view of the cluster, but set him hot on the trail of a new and wonderful mystery. Yet Scotty was magnanimous; he resisted the temptation to g°

Several years ago I received a letter from Tommy Christensen, who lives in Odensa, Denmark, and observes with a 3Z-inch refractor. Along with a _crjption of M33 and the Veil Nebula was a brief note about the open star clus-NGC 6811 in Cygnus (Figure 9.7). He called it one of thc most beautiful clus-^te he has seen and mentioned "a dark band about 5' thick running through the ^|L1jdle of the cluster, not completely without stars, but nevertheless conspicuously dark." He also likened it to a "smoke ring" of stars.

Figure 9.7

Does the open cluster NGC

6811 in Cygnus appear to have a dark center as seen through your telescope?

My recollection of NGC 6811 was of an unimpressive, nondescript group of stars near Delta (5) Cygni. A quick look through my notes showed no reference to a ring of stars. Furthermore, I checked observing guides and my file of reports from amateurs. Again, nothing unusual was mentioned. A 6-inch instrument will show some 75 faint stars shimmering inside an area 15' across. It reminds some amateurs of an opera-glass view of the Beehive Cluster in Cancer.

A print from the photographic Ross-Calvert atlas did, however, suggest that GC 6811 has a dark center. But the cluster is not well resolved on the print, and ¹¹ s diffi_cu]t to compare a blue-light photograph with what is seen visually. I could ^ave waltzed out to my telescope and settled the matter, but I thought it better ^to solicit comments from readers; this I did in my September 1985 column. I was P^Urposely cryptic, asking only if anyone had seen something “unusual" in NGC

Observers took the bait! In poured scores of letters. It’s quite impossibl tell just how many people reported observations. Some letters contained ments from a single observer, while others offered the consensus of as many⁰¹' 20 amateurs at a star party.                                                ’ ^as

The reports came equally divided in thought. One group assumed the clust formed some kind of figure. There were letters extolling bells, butterfli^ dinosaurs, and a pair of fighting peacocks, and one delightful comment from * person who saw “Nefertiti’s head-piece." Several of those who wrote saw th_rc ? leaf clovers, and one amateur went whole hog for a four-leaf clover (his friend however, saw a frog!). Using several 17-inch telescopes at the 1985 Astrofest ’ Wisconsin, I saw the cluster as either a butterfly or rotifer outline.

The other camp comprised observers who saw a dark center in NGC 6811 They also usually mentioned dark lanes. One even used Christensen’s term “smoke ring.” A young observer from Ohio simply said “stars in a ring."

This is a beautiful, albeit minor, example of how people see things differently Everyone was looking at the same cluster, but because of experience, conviction or psychological factors, each saw it in a different way.

I expected some correlation between telescope aperture and visual description. To some extent this was true. The largest telescope used to report a “dark center” was an 11-inch reflector. The smaller the telescope, however, the more pronounced the feature appeared. With apertures of 16 inches and larger, the dark center just doesn’t seem to show. So how can we say what is the “real”

description of the cluster?

Then I got a letter from Marton Konecny of Czechoslovakia. He observes with a 2’/2-inch Zeiss refractor and magnifications from 14x to 140x. While Konecny comments that Americans might think this a small instrument, it is about the standard amateur telescope in his country. He too saw NGC 6811 as a clear cut ring of stars with no hint of the butterfly pattern I had once suggested in an earlier column. I only hope he gets a chance to view through a 16-inch someday! Konecny sent a drawing of NGC 6811, which is unusual in that it records a glow around some of the stars. Have others noted this?

Hunting Cosmic Pearls in Aquila

Aquila, the Eagle, soars highest on cool September evenings. Its brilliant ice-blue gem, Altair — the southern star of the Summer Triangle — adds a flash of sparkle to the lacy boundaries of the Milky Way that brush past this celestial raptor. Despite its prominent placement, Aquila contains some interesting objects, but surprisingly few are truly spectacular. Aquila does have a bounty of planetary nebulae, however, which are within the reach of amateur-sized telescopes. Until Scotty began introducing them to his readers, these cosmic pearls, as he referred to them, were largely ignored in the popular literature. Here Scotty introduces us to several planetaries in the neighborhood of Altair. Many of them have gone unseen, becaus

|,_ey are not plotter! on some popular sky atlases, such as Wil Tirion's Sky/tt/as 2000 O' Furthermore, published magnitudes for faint planetary nebulae are usually Fjj_snially underestimated, causing many amateurs to shy away from them. But times, eqU'P^ment' ^ar*d knowledge continually change, and Scotty was right on top of I _ew observing trends, as we shall see.

September brings a slack tide of celestial treasures. As twilight gives way to dark, the golden sands of Sagittarius remain in the south and the Northern Cross in Cygnus still floats overhead. But nothing very new or dramatic is coming ^UP >^{n t}*^{qe easL} Th°^{sc w}h° observe late into the night often have their first taste of the crisp autumn air that will follow as days grow shorter. And just before dawn the luminous cone of zodiacal light rises from the eastern skyline. It is one of the most pleasant times of the year to be out under a starry sky.

The evening meridian is dominated by the three brilliant stars of the Summer Triangle. At its southern apex is lst-magnitude Altair, a celestial neighbor located only 16 light-years from Earth. In my mind’s eye I see Altair wrapped in a galactic blizzard of tiny luminous spheres. We know them as planetary nebulae, pearls on the grand scale of the galaxy.

Until a decade or two ago most deep-sky observers concerned themselves with only the few bright planetaries large enough to show some detail in small telescopes. Objects like the Ring Nebula in Lyra and the Dumbbell in Vulpecula were standard fare at summer star parties. Although a handful of amateurs observed others, hardly anyone dreamed of searching for the tiny glowing gas bubbles scattered around Altair. Indeed, few even knew they were there!

Times have changed. Today’s observers have access to larger telescopes. They have better catalogs of deep-sky objects, and, more important, better star charts. They also have nebula filters. Today’s observers eagerly venture into cosmic depths that their counterparts of a generation ago hardly knew existed.

Perhaps the best place to begin our search for Aquila’s planetaries is on the pages of Uranometria 2000.0.1 consider this atlas among the best ever made for observers. The charts have a generous scale, with 1° equal to about % inch. This is roughly the same scale as the finder charts that have endured through more than 80 years of use by the American Association of Variable Star Observers. Plotting a position on the Uranometria 2000.0 charts is easy because epoch 2000.0 grid lines are shown for every degree of declination and, except near the ^celestial poles, for every four minutes of right ascension. Stars are shown to ^about magnitude 9.5, the average limit for a 2-inch finder, and more than 10,000 d^eeP-sky objects are plotted.

But there’s more to deep-sky observing than just knowing the location of an °hject. Without such basic information as its size and brightness, we could sweep °^Ver °ur target and not even know it. A lOth-magnitude planetary that’s 5' in ^lameter is going to look a lot different from one only 5" in diameter. To that . ^Cnd’ observers will welcome Uranometria 2000.0's companion volume, The

Deep-Sky Field Guide by Murray Cragin, James Lucyk.and Barry Rappap_Orj I gives basic information about all the deep-sky objects plotted in the atlas. [| • arranged by chart number, making it particularly useful in the field, since inf *^S mation about all the objects on one chart can be found on one page (or sev ' adjacent pages).                                                             ^al

Altair is on chart 207 of Uranometria 2000.0. The corresponding page of 77 Deep-Sky Field Guide lists a dozen planetary nebulae. Of these, only three * front the NGC; the rest are from more modern compilations. Since almost al] th NGC objects were discovered visually, they are generally the easiest to see amateur telescopes.

One of the objects to which Smyth calls attention in his classic A Cycle of Celestial Objects is NGC 6804. It is small, only about 1' in diameter (Figure 9 8) He comments that in “very powerful" telescopes NGC 6804 appears fan-shaped William Herschel, who discovered the object, thought he could resolve it j_nt₀

Figure 9.8

Seemingly lost among the multitude of stars in the Aquila Milky Way is NGC 6804, a planetary nebula some 4,700 light-years distant.

component stars and thus placed it in his class VI (very compressed cluster of stars). Norton’s Star Atlas once carried the Herschel number 38⁶ for this object, although we now know it to be a planetary nebula.

Careful examination of NGC 6804 with different apertures would make an interesting project at a star party of serious observers. It is about 30" in diante ter (the minimum size of Jupiter) and 12th-magnitude. Its visibility depends heavily on sky conditions. I have seen it on several occasions here in Connection¹ with a 4-inch Clark refractor, but not in recent years with our increasingly polluted skies. My observing notes from the 1950s in Kansas always call the pl^jn etary “easy” in a 10-inch reflector.

0ne of the great pleasures of deep-sky observing is the individuality that cer-in objects acquire in the eyepiece. I'm always delighted to learn that someone _ees an object in a new perspective. One such example comes from Robert [vfoseley of Coventry. England, who tracked down NGC 6804 while testing a new |0-inch f/6 reflector. His best view was at 120x. He writes,"It gives the impression fa highly condensed but partially resolved cluster. It is a faintish oval nebulosity with a 12th-magnitude star toward its northeast edge. With averted vision at least one other star could be seen superimposed on it." Moseley questioned the 13th magnitude I had given for NGC 6804 in an earlier column. Published magnitudes for planetary nebulae cause many disagreements, and I believe it is best to slightly mistrust all of them and to record your own magnitude estimates with your notes.

Just 50' to the north is another planetary. NGC 6803 is only 6" across and 11th magnitude, which should give it a much higher surface brightness than NGC 6804. Oddly enough, however, my observing notes suggest that I have had a more difficult time with this object.

Most of the other planetaries on Uranometria 2000.0 chart 207 are less than 10" in diameter. As such, they appear starlike at the low magnifications most observers use for hunting down objects. But planetaries emit most of their light at a few discrete wavelengths, especially two emission lines of doubly ionized oxygen near 5000 A. Some enterprising amateurs have attached small, narrow prisms to telescope eyepieces to distinguish between faint stars (which have their light drawn into short streaks) and the tiny planetaries (which remain starlike).

Another trick is to use a nebula filter (such as Lumicon’s O III filter) that isolates the oxygen emissions. The narrow passband of this filter dims surrounding stars because it blocks most of their light while leaving the planetary’s brightness relatively unchanged. Repeatedly flicking the filter between the eye and eyepiece causes the planetary to blink, making it easy to identify which “star” is the nebula.

If you are prepared for the challenge, here are three planetaries that will test your abilities. I have never seen any of them. Furthermore, because the light of a planetary is confined to a few wavelengths, I question how its brightness determined by conventional methods (usually involving photography) compares with what the eye sees.

PK 52-2.2 (the designation is from the Catalogue of Galactic Planetary Nebulae by Lubos Perek and Lubos Kohoutek) is less than 10" across and 12th magnitude, 'rhe Deep-Sky Field Guide notes that it has a "ring structure.” If you ^Can locate this object, its appearance will serve as a reference for the other small Planetaries. It has a 14th-magnitude central star.

PK 45-2.1 is less than 5" across. Although it is listed as visual magnitude 12.7, ^lls smaller size should give it about the same surface brightness as PK 52-2.2 if you use very high power. It is listed as having a “stellar image.”

1 suspect that the most difficult of the three is PK 52-4.1, which is less than 10" ^ln diameter and magnitude 13. If you succeed here, you can test your skill on sev-^eraI even fainter planetaries listed in the Deep-Sky Field Guide.

SEPTEMBER OBJECTS

Ast = Asterism; BN = Bright Nebulo; CGx = Cluster of Goloxies; DN = Dork Nebulo; GC= Globular Cluster; Gx = Goloxy; OC = Open Cluster; PN = Planetary Nebulo; * = Stor; * * = Double/Mulliple Star; Vor = Vorioble Sfor

SEPTEMBER OBJECTS (CONTINUED)

1