OCTOBER

The Great Square of Pegasus

Compared with the brilliant, star-studded sky of winter, the autumn sky is but a vast celestial prairie of feeble suns. Even Pegasus, whose Great Square is the season's hallmark asterism, appears drained of starlight to the naked eye. And though the Square is one of the most familiar of all star patterns in the sky, it is also one of the more difficult for beginners to find, because of its large size. On a star chart, the Square appears so small. But Pegasus is enormous. It is the seventh-largest constellation, covering 1,121 square degrees of sky. Yet, despite this size, Pegasus is not a cornucopia of conspicuous deep-sky objects. In fact, it has only one Messier object, the globular Ml 5. Scotty, however, was a digger, and you could leave it to him to find any telescopic nuggets. "Whether you use a 2.6-inch refractor or a 29-inch reflector," he wrote of Pegasus, "there is plenty to delight your eye."

October is a most auspicious month for amateur astronomers. The summer haze and humidity have given way to cooler days and crisp, clear skies at night. Darkness comes earlier, dewing of a telescope’s optics is generally less of a problem, and the sky is not so jammed with star clouds that confusion rules.

The Milky Way stretches from east to west across the northern star patterns, but here we are looking in the direction approximately away from the center of the galaxy. Star swarms marking the galaxy’s plane are thinner, and it is easy to star hop and make finder searches for objects embedded within them. Some of the most beautiful sights for small telescopes are in and around this corner of the Milky Way.

Overhead the Square of Pegasus dominates. As a small boy I thought of the Oreat Square as a baseball diamond where the Norse gods Odin and Loki pitted their mythical teams against one another — stray meteors were pop flies and ^cl°uds meant the game was called on account of rain. To my father’s dismay, I ^al»ays rooted for Loki!

Only schoolchildren and a few ROTC veterans of the U. S. Army and Navy are familiar with the old Star Atlas and Workbook of the Heavens, published by American Education Publications. Although long out of print, the 32-page booklet was used heavily in schools during the late 1960s and early 70s. It container a novel method for learning the easily recognized constellations. Rather than having the Big Dipper as a starting point, it had a key constellation for each season: Leo, Scorpius, Pegasus, and Orion for spring, summer, fall, and winter respectively, 'rhe reason was simple. As the Dipper's position around the p₀|_e changes with the season and time of night, its pattern sometimes becomes difficult for beginners to locate.

Tests of pattern recognition showed that difficulty can arise if a star chart i_s rotated just 15° with respect to the sky. Furthermore, the concept of seasonal key constellations grew out of research done during World War II at the celestial navigation school at Selman Field in Monroe, Louisiana; this system produced the best constellation learning among the 500 cadets tested. The key asterism for fall was the Great Square of Pegasus (Figure 10.1). While none of the Square’s stars are 1st magnitude, it dominates October’s star-poor evening sky. Counting the stars within the Square is a good indication of the sky's limiting magnitude. For example, if you see 13 stars you are reaching magnitude 6.0.

Figure 10.1

The Great Square of Pegasus is the starting point for many autumn star-hops.

How many naked-eye stars can be seen within the Great Square of Pegasus? A quick look at the Skalnatc PlesoAr/as of the Heavens suggests more than 100-but many of the stars plotted are below the traditional 6th-magnitude naked-ey^e limit. However, with dark skies and good transparency, many observers report glimpsing stars as faint as 7th magnitude. And in 1901, the Lick Observatory astronomer Heber D. Curtis found that, by shielding off the light of the sky a taking other precautions, he could just detect stars of magnitude 8.3.

One answer to the Pegasus question comes from John Bartels, who counted 38. . mentions, however, that some high cirrus clouds may have interfered.This sug-sts his limit was magnitude 6.6. If you push your limit to magnitude 7.0. then 70 ftars should be visible.

j^_ow many deep-sky objects are visible in Pegasus? The present-day list in Robert Burnham’s magnum opus, Burnham's Celestial Handbook, carries 23. Moreover, in the text there is mention of the famous “Stephan’s Quintet," which ffectively adds five more galaxies to the list. During the years of writing this column I have discussed 16 objects in Pegasus. Despite the apparent paucity of deepsky targets, the number of objects given in the various handbooks is appropriate for typical amateur instruments in use at the time the books were published. However, in the years that have passed since Burnham’s complete work became available, the size of amateur telescopes has increased greatly. The rise of the Dobsonian reflector has been a major reason.

Telescopes of 17-inch aperture are now off-the-shelf items of modest cost.There are a dozen or more amateur groups in the United States that either now have or are completing instruments with apertures of 24 inches or more. Such light-gathering power brings within reach of the backyard observer virtually every deep-sky object in the NGC and IC compilations. Titus the Great Square of Pegasus alone contains more than 100 suitable objects.

Not all the objects are easily located. So, if you do your searching with a finder, it is important to know the size of its field of view. Use a star atlas to determine the distance from an easily identified star to the object of interest and then offset from the star with the finder. You can try this method on NGC 16, a tiny galaxy r/2⁰ south of the bright star Alpha (a) Andromedae at the northeast corner of the Square of Pegasus. (Although the star is officially in Andromeda, it is sometimes marked on charts as Delta (5) Pegasi, which refers back to when some stars were shared by the two constellations.)

If your finder has a 3° field, and you place Alpha Andromedae at its northern edge, NGC 16 should be just about centered. This elliptical galaxy is only T in diameter and 13th magnitude. With a 6- or 8-inch aperture, scan a 30x or 40x field with your eye for an object that is a bit too big to be a star. It is best not to sweep lhe telescope for this galaxy since an object this faint will probably be rendered invisible if the field is moving. Once you suspect you have the galaxy, higher magnification can be used to confirm it.

Another good star from which to begin a search for galaxies is Alpha (a) Pegasi ^at the Square’s southeast corner. Just about 3° to its south is NGC 7479. a barred ^sPiral that appears just over 3' long and a bit brighter than 12th magnitude (Figure ^•2). If you have a motorized mount, you can also set on Xi (£) Pegasi and wait minutes for this object. If your eye is properly dark-adapted, the galaxy should be visible in even a 3-inch telescope, but a 6-inch is better. A cloth over your head ^and the eyepiece gives good protection from stray light. I have seen it easily with

4-inch Clark refractor, but with this small an instrument it is not possible to see ^anV detail. On the other hand, the 12-inch f/17 Porter turret telescope at Stellafane

Figure 10.2

Just about 3° south of Alpha (a) Pegasi is NGC 7479, a very asymmetric spiral galaxy with a bright, long bar and looping spiral arms. Star formation occurs over the entire visible portion.

in Springfield, Vermont, offers a more interesting view. At 300x the central bar is obvious, and there is a hint of a spiral arm at one end.

A 12-inch f/5 reflector set up near the Porter telescope did not offer as good a view of NGC 7479 even though I thought the mirror was good. It may have had something to do with the longer focal length of the Porter telescope, or a better eyepiece. The importance of fine-quality eyepieces has been overlooked by many amateurs. Recently several types of expensive but very high-quality eyepieces have come on the market. Judging from my mail, it seems that these oculars distinctly improve the deep-sky performance of a telescope. Objects once considered only within the reach of large amateur instruments are being seen in smaller telescopes equipped with fine eyepieces.

Several other small galaxies lie near Alpha Pegasi. NGC 7448, an 11.8-magni-tude spiral located I/2⁰ northwest of the star, is about 2' long and half as wide. Like NGC 7479, it is readily seen with the 4-inch Clark. However, increasing the aperture does not improve the view other than to make the object appear brighter. My old 10-inch reflector in Kansas simply showed it as a featureless glow.

NGC 7454 is a challenging galaxy, located about /2⁰ northcast of NGC 7448. Although more than a magnitude fainter, its surface brightness appears nearly the same owing to a diameter of just 0.5'. At low powers NGC 7454 is easily mistaken for a faint field star. It, too, appears quite featureless even with a large tele scope. A few years ago I had a peek at it with a 16-inch reflector, and though ¹ was easily seen, no detail was visible. For an instrument of this size, there exist

_qrly a dozen more galaxies in the immediate area — all below thc 13th-magni-* . limit for galaxies plotted in Tirion’s Sky Atlas 2000.0 but listed in thc Revised General Catalogue of Nonstellar Astronomical Objects (RNGC).

magnitudes listed for galaxies are often deceptive to the amateur observer the visibility of one of these dim glows depends on its size and shape, in jition to its overall brightness. A 4-inch telescope can sometimes reach 12th-'* nitude stars, but this does not mean that it can show 12th-magnitude galaxies. _o facts might encourage the amateur. Almost all the entries in the NGC were discovered visually. In addition, long practice improves the ability to detect faint objects.

Here are some test galaxies of differing difficulty, located in Pegasus. Much of the difficulty in finding a faint object is avoided when one knows just where to look among the field stars. First look for NGC 7678, a 1.7'x 1.1'spiral; I saw it with _a 10-inch in Kansas and it is easy in the 20-inch refractor of Van Vleck Observatory. NGC 7469 is a 1.3' x 1' spiral and slightly fainter. I could not find it with a 6-inch refractor but years back I viewed it in a 13‘/2-inch reflector. For a very demanding test, try NGC 7619 and 7626, a pair of tiny elliptical galaxies of about the 12th magnitude. In the 20-inch they could be seen with some difficulty, but a 4-inch refractor was insufficient on a good night. What is the smallest aperture with which you can fish out this pair?

Can someone explain NGC 7772, which Norton’s atlas shows inside the Great Square of Pegasus? It is missing from the Atlas of the Heavens, but the NGC describes it as "a cluster of scattered stars of about 10th magnitude.” However, I see no particular concentration of stars in its place. The original discovery seems to have been by Sir John Herschel.

Finally, a bit of observing trivia: who knows how close on the sky the first and last entries in thc NGC lie? NGC 1 is a 12.8-magnitude (my estimate with a 10-inch reflector) galaxy in Pegasus. The last entry in the original 1888 catalog is NGC 7840, but a 1973 revision by Arizona astronomers Jack Sulentic and William Tifft states that the object was not found on photographs made with the 48-inch Schmidt telescope in California.Thus, the last real object appears to be NGC 7839 —■also in Pegasus and at essentially the same declination as NGC l.The positions in the original catalog place NGC 7839 only 5.6' southwest of NGC 1. However, NGC 7839 is very faint (it does not even have a listed magnitude in the revised NGC) and may be well beyond the reach of most amateur telescopes.

Using the list of objects in Vol. 2 of Sky Catalogue 2000.0, which is well suited f°^r amateur instruments. I find the closest readily observable object to NGC 1 is UC 7819, a faint galaxy in Pegasus. It is about 3.8° north of NGC 1.

Thus, NGC 1 and NGC 7839 are the first and last valid entries in the NGC, and ^{11 s}° happens that these galaxies are separated by less than 6' on the sky. NGC 1 about 1' across and, by my estimate, about magnitude 12.8. It forms a pair with .    2, which is more than a magnitude fainter and 2' to the southeast. NGC 7839

^ls even fainter and 5!6' southwest of NGC 1.

Although NGC 7840 is technically the last entry in the NGC, it app_arc doesn't exist even though it was reported by such an outstanding observer Albert Marth, who worked with William Lassell’s 48-inch reflector on the i i ^3S of Malta.                                                               ^and

Two Spectacular Autumn Globulars

"Some deep-sky objects are remembered for their beauty, others are cherished f_Or their scientific importance," Scotty wrote. "Some are sought out as test objects to establish the excellence of a telescope, observer, or atmospheric condition, and there are those best known for their unusual features." Finding any one object to meet all these criteria would be hard, but two autumn objects fit many of the categories — the splendid globular clusters M15 in Pegasus and M2 in Aquarius For many observers, globular star clusters encapsulate all that is stunning and test-worthy. For instance, both M2 and M15 hover at the limit of naked-eye visibility, presenting an enjoyable challenge for dark-sky observers. Resolving the cores of these globulars with small telescopes is equally challenging, no matter where one lives. And their visual appearance has sparked controversies that have persisted for decades. For instance, are their disks colored? Are they marred by dark lanes and patches? Scotty believed that observers had overlooked such features for nearly a century.

The archetype of modern observing handbooks for amateurs is William H. Smyth’s Bedford Catalogue. When this English observer prepared his classic as the second volume of A Cycle of Celestial Objects in the early 1840s, he mentioned only two deep-sky objects in Pegasus.This is unusual considering that it is the seventh-largest constellation. There is little doubt that Smyth was acquainted with more “nebulae” in Pegasus, for he had access to earlier catalogs, especially the great works of the Herschels. However, he chose only those that he felt amateurs would be interested in viewing.

In 1859 Thomas W. Webb published Celestial Objects for Common Telescopes. In many respects it relied heavily on Smyth's work. Webb originally included only one deep-sky object for Pegasus. He added a second in later editions, but it was different from Smyth’s selection. Other observing guides added more.

All handbooks from the time of Smyth agree on including one object in Pegasus — M15 (Figure 10.3). Although Messier first saw it in 1764, it had been discovered by Jean-Dominique Maraldi in 1746. (Incidentally, some sources incorrectly state that Maraldi discovered M15 while searching for De Cheseaux’s comet of 1746, when it was actually M2 that he found then )

M15 (also called NGC 7078) is easily located about 4° northwest of Epsil°ⁿ (e) Pegasi. It is one of the few Messier objects easily picked up by sweeping-Make the first sweep northward from Epsilon by turning the declination axle-and stop after going about 5°. Now move one field to the west and move so I,_v the same amount. Repetition of these steps, as if mowing a lawn, should bring jje telescope across the field of M15 in a short while. This globular is unmistak-ble because there is a 6th-magnitude star beside it in the same low-power field. Recording to Sky Catalogue 2000.0, M15 is about 12" across, with a V magnitude _of 6 35- Th’^s magnitude, derived from photoelectric measurements, is close to hat th^{e e}Y^e sees.Therefore, Ml5 should be visible to the naked eye. Remember, though, that eyes vary from person to person, not to mention over time (I see red tars brighter now than I did years ago), so the actual perceived brightness of an object is never completely fixed. One way to improve the chance of seeing it without optical aid is to look through a long cardboard tube painted black on the inside. This will cut down the often unappreciated flood of sky brightness and improve your magnitude limit.

The view of M15 is impressive with anything from binoculars to the largest telescope.Telescopes of 4-inch aperture and less will not resolve the core of Ml5. Mv 4-inch Clark refractor at 40x shows M15 as a slightly oval disk, more luminous in the center, with edges just beginning to break up into individual stars. Increasing the magnification enhances the view, and at 200x stars at the center

Figure 10.3

The core of globular cluster M15 in Pegasus is extremely densely packed, suggesting that a sudden, runaway collapse due to the gravitational attraction of many stars in a small region of space may be occurring.

°f the cluster start to be resolved. I once succeeded in resolving the core with my °>d 10-inch f/8.6 reflector and a low-power eyepiece coupled with a Barlow lens Y'elding 200x. However, the same ocular combination on a 12-inch f/5 instrument did not break the center up into individual stars completely. I have always ^rec°mmended using a Barlow for boosting magnification. Eye relief is better, and dust on the ocular scatters less light than if an equivalent high-power eye-P*^ece is used alone.

I had an astounding view of the cluster with a 17-inch reflector and 9,_n, Nagler eyepiece. M15's stars nearly filled the field. I also remember vivid] ₍ breathtaking view of this globular cluster many years ago with the 36-inch ref]_e(;^a tor at Steward Observatory in Arizona, which showed stars splashed all over th field of view. Stars literally erupted in the eyepiece field, and with averted visi₀^C the cluster's stellar population seemed to double.

The outer reaches of the cluster arc so frayed that the eye cannot tell where ' ends. Smyth commented on star chains radiating outward from the cluster i have confirmed this appearance with the 4-inch Clark refractor at my Joseph Meek Observatory. But 1 find more interesting a remark by T. W. Webb who wrote, “Buffham, with 9-in. spec, finds a dark patch near the middle, with 2 faint dark 'lanes’ or rifts, like those in M13, unnoticed by h.or D’A. "Are we to believe that a 9-inch speculum-metal mirror could show features that were missed by the skilled eyes of John Herschel (h.) and Heinrich d'Arrest (D’A.), or are these dark markings just an illusion? My notes also do not mention any of the dark patches suspected by John Mallas when he observed with a 4-inch refractor. Perhaps some amateurs would like to check on the existence of such features.

For years, dark lanes reported in the Hercules globular M13 were also thought to be illusions, but several years ago they were rediscovered by amateurs and are now common fare at star parties. Visibility of the M13 markings depends on telescope aperture and magnification. Perhaps those in M15 are similar. October is prime time for amateurs to give M15 a good working over with different telescopes under a wide range of conditions. Although I encouraged amateurs with 16-inch and larger instruments to follow up these reports. I’ve never had the patch or lanes confirmed. It’s worth pursuing because professional astronomers have found dust clouds in the southern globular NGC 362. Although their work is based on CCD observations and image processing, it seems reasonable that some dust clouds could be visible to the eye.

In the past I have mentioned a planetary nebula within M15. Known as Pease 1 and located on the cluster’s northeast side, it was discovered in 1927 on photographs made with the 100-inch reflector at Mount Wilson Observatory. I had always considered this tiny (1") 14th-magnitude object probably beyond the reach of any amateur telescope, but recently three observers sent interesting reports. All used the Lumicon O III filter to locate the planetary with the blinking method. By flicking the filter in and out between the eye and eyepiece, the planetary appeared to blink relative to the stars.

On to M2!

The distance to M15,40.000 light-years, is similar to the 50.000 value listed for M2, our other spectacular autumn globular (Figure 10.4). One way to pick up J* is to aim your telescope a quarter of the way from 3rd-magnitude Beta IP Aquarii to 2nd-magnitude Epsilon (e) Pegasi. You will find a great glowing heap of stars, with the brighter ones sprinkled like stardust over a disk 10 °^r across. M2 has a total visual magnitude of 6.3. Thus one would expect it to be ble to ^t*^{ie na}*^<e^ ^ey^{c un<}Jer excellent observing conditions, but such sightings are uncommon.

-The famous variable star-observer and comet discoverer Leslie Peltier finds a more difficult object for the unaided eye than M33, the large spiral galaxy in Triangulum. In the clear dark skies over the Yucatan Peninsula in Central ^nierica I could view M33 directly, but M2 required averted vision before it could be glimpsed directly. But I have seen M2 often with the naked eye in Kansas. Missouri. Arizona, and even from the bayous of Louisiana. M2 is one of •hose happy objects that are a delight in any size instrument. Binoculars give enough detail to keep the amateur interested, while the view I once had with Wesleyan University’s 20-inch Clark refractor was spellbinding.

Figure 10.4

Fully 37 percent of the light from the globular cluster M2 in Aquarius comes from the stars populating the cluster's central square arcminute.

M2 was discovered by Maraldi in September 1746. Because he could not resolve the glow into stars, he initially mistook it for a comet. Indeed, when Charles Messier first saw M2 some 14 years later, he did not resolve it into stars ^e>ther and likened the cluster to the nucleus of a comet. Interestingly, in today’s 'nstruments, 13th-magnitude stars on the fringes of M2 can be glimpsed in an 8-^lnch, but in a 4-inch the cluster is generally unresolvable and condensed like a ^c°rnet. In fact when a number of observers independently discovered Comet Kobayashi-Berger-Milon (1975h) in the same field as M2, it was not possible to ^tell the globular from the comet until the comet’s motion tagged it.

Smyth mentions that an observer named Samuel Vince viewed M2 with miani Herschel’s 40-foot reflector in 1779 and saw tiny stars right to the cen-

ter of the cluster.Today, a good 12-inch telescope can resolve M2 even to its _c as I have seen it with the Porter turret telescope at Stellafane. Using this in ■< ^C’ mcnt I find John Herschel’s description of M2 most suitable, for he called cluster “a heap of fine sand."                                                 ^e

Two observations of M2 in recent times warrant attention by amateur Kenneth Glyn Jones in his Messier's Nebulae and Star Clusters mentions a f_aj_n^ greenish-blue glow around the cluster under certain observing conditions j_oj_ln Mallas, who used a 4-inch refractor, reported seeing a dark lane crossing th northeast corner of the cluster. Perhaps some astrophotographer could invest; gate Mallas’s dark lane by taking a set of different exposures. By the way, Steve Coe of Glendale. Arizona, writes that M2 has “lovely chains of stars meanderin outward from the core, and several dark lanes are visible.”

Sweeping Through Sagitta

After darkness falls in mid-October, look halfway up the sky, just west of the meridian and just north of scintillating Altair. There you will see four close-knit stars marking out Sagitta, the celestial Arrow. Sagitta is one of the best known of the very small constellations, mainly because amateurs use it as a guide to the famous Dumbbell Nebula in dim Vulpecula. Although Sagitta is small (its official boundaries have varied over time), it now covers an area of 80 square degrees, making it the third-smallest constellation. The constellation lies in a rich section of the Milky Way and hosts a bounty of celestial riches, including the once mysterious and ambiguous star cluster M71 and a neglected open cluster known as H 20. "So sparse is this cluster," Scotty wrote, "that without careful positioning of the telescope it is easy to overlook."

As a child I would stand outside on autumn evenings and fantasize about the constellations. I would watch as the horse-archer Sagittarius shot a golden arrow at Scutum (Sobieskii’s Shield). The arrow would strike the top of the shield, tearing a great hole in it, and the fragments would fall back together as the arrow-shaped open cluster Mil.The arrow would then soar upward into the star clouds, where it would hang poised for another target in thc Milky Way or perhaps another galaxy or even some imaginary other universe.

Now, over half a century later, the arrow Sagitta (Figure 10.5) still hovers where I saw it as a child. When first described by Eratosthenes, this little con stcllation consisted only of a group of stars running 4° from cast to west. By 'he 19th century, map makers had enlarged its area to 10°, and when 'he International Astronomical Union reorganized constellation boundaries in 'he 1920s Sagitta’s territory grew to 20° across, where it will probably remain.

As old as it is, however, Sagitta seems to be little observed. It lies in a Milky Way star cloud, so the field is swamped with faint stars. The a/ ’ , describes numerous NGC objects in this part of the sky as “nonexistent-pjovvcver, this usually means that the object, though recorded by earlier _obs^crvers' ^{was not} f°^und ^on photographs examined by thc authors of the Rpj(jC- As many amateurs know, a group of stars that stands out as a cluster in telescope can become lost on a photograph, especially if the field is full of faint background stars. An interesting project, though one with little promise of fame, _ould he to search visually using, say, a 12-inch telescope, for the objects listed _s nonexistent or “not found” in the RNGC.

Figure 10.5

The constellation Sagitta straddles the Milky Way and points to several deep-sky wonders. South of it lies the constellation Aquila, with the bright star Altair.

One cluster not easily overlooked in Sagitta is M71. Indeed, it was visible with my childhood 1-inch 40x refractor. You will find it south of the center of a line running between Gamma (y) and Delta (8) Sagittae, about 20' northeast of 6th-magnitude 9 Sagittae in the shaft of the arrow. I have always wondered why Messier saw so little in the cluster (Figure 10.6). He described it as very faint with ⁿ° stars and wrote, “The least light extinguishes it.” Maybe it was a poor night ^when he examined M71, which was brought to his attention by Pierre Mechain ^ln ^80 (after being discovered by earlier observers). On fainter objects, Messier ^Usually saw more detail.

With medium magnification, my 4-inch Clark refractor shows individual stars ^ather uniformly distributed across the 8th-magnitude cluster. M71 has been

Figure 10.6

Once an object of contention, M71 in Sagitta is now recognized as a loose globular cluster rather than a rich and remote galactic cluster.

called both an open and a globular cluster. The early 20th-century dean of visual observers, E. E. Barnard, noted that M71 looked like a globular cluster in his 6-inch refractor. And the French observing handbook Revue des constellations gives this description: “In 10 x 50 binoculars and a 2'A-inch refractor at 20x, well seen, large and diffuse. Globular appearance, detached in a rich field, unresolved, with 3’Z-inch refractors at 30x to 45x. Fine cluster 6' by 5', some stars visible with an 8-inch reflector (150x); about 20 stars of magnitude 12 and fainter, on an irregular milky background, in a 12/2-inch at 80x.”

My old 10-inch f/8.6 reflector, which, with its %-inch-thick plate-glass mirror, was essentially a forerunner of today’s Dobsonians, gave a magnificent view of M71 at lOOx. Stars were visible across the entire disk, and the object looked decidedly like an open cluster. The 20-inch Clark refractor at Wesleyan University's Van Vlcck Observatory in Connecticut shows something more globular. Volume 2 of Sky Catalogue 2000.0 terms M71 “globular" without mention of any earlier controversy.

Many observers have commented on M71’s arrow-shaped appearance, but in photographs it is usually round. Its image in Hans Vehrenberg’s Atlas o) Sky Splendors is quite triangular. What do you see? Most observers iind t object uniformly illuminated, with no central core. Yet in the Messier All’^iun^ John Mallas drew the cluster with a pronounced bright edge, rather boomerang. I find no mention of such a feature in my observing notes, but ^_ebb Society Deep-Sky Observer's Handbook for open and globular clusters mentions a "nebulosity concentrated in the western part." What do you see? Remember to record the size and magnification of your telescope.

y\bout !6° south-southwest of M71 is the scattered group H 20. a very sparse bunching of about 15 stars in an area 7' across. They have a total magnitude of ■7 7 which makes the cluster brighter than M71. However. H 20 is much more difficult to pick out from the background sheen of the Milky Way. as compared with the tightly packed but fainter stars comprising M71. Here is a clear case of not being able to judge the conspicuousness of a cluster from its published magnitude alone. Experienced observers know not to draw a mental image of an object by its listing in a catalog, regardless of the amount of data given. So sparse is this cluster that without careful positioning of the telescope it is easy to overlook. Often, sweeping the area with a 4- or 6-inch telescope will fail to locate it. So inconspicuous is this object that it was not included in the NGC compilation.

To the west and a little north is a delicate splash of faint celestial fire known as NGC 6802. This small cluster is rather strongly elongated north-south. As a guide, there is a small grouping of stars to the west called Brocchi’s cluster, and NGC 6802 is at the east end of a 2°-long string of stars easily seen in any telescope.

The eastern end of Sagitta contains three very challenging planetary nebulae. Sky Catalogue 2000.0 lists NGC 6886 as 4" across and of photographic magnitude 12.2. In the early 1900s Heber D. Curtis made a composite drawing of this planetary based on photographs exposed from 10 seconds to an hour. In addition to calling the object 10th magnitude, he sketched it as 6" across. He also noted two projections that make the planetary look like a low-resolution photograph of Saturn. To date these projections have escaped my visual searches even with the 20-inch Clark. Perhaps someone can look for these features with one of the 29-inch Dobsonians now turning up across the United States.

The main disk of NGC 6886 is within the reach of a 4-inch telescope, but a word of warning is in order: Under poor seeing conditions the planetary may be difficult to distinguish from its surrounding stars. Todd Hansen of Potter Valley, California, used a 10-inch f/5.6 Newtonian to view the nebula. He notes it as “extremely small, bright, and slightly oval; at 180x sometimes like a fuzzy star; sometimes almost seems double.”

Another small planetary is NGC 6879. It is listed as 5" in diameter and photographic magnitude 13.0. Hansen could not make out the planetary’s disk. In •he Webb Society Handbook (Vol. 2) Pat Brennan reports that NGC 6879 appears stellar in an 8-inch reflector. He identified the planetary by using a small Pnsm at the eyepiece of his telescope. This simple accessory spreads the light of ^stars out into tiny spectra, while the planetary remains as a dot since its light is ^essentially from a single emission line at one wavelength.

Another planetary best detected with a prism is IC 4997. Its 2" disk is listed as P °tographic magnitude 11.6, and it has a central star perhaps two magnitudes ^nter. Hansen, probably on an especially good night, thought he could distin-^,sh the star at 360x but failed to do so on another night. English amateur Ed

Barker saw a slight indication of the planetary’s disk at 308x. At the time using an 8/z-inch reflector.

Although American amateurs have lagged behind their European counter parts in using a prism to locate small planetary nebulae, they have been quick use nebula filters. These dim the field stars while leaving the nebula’s brightn relatively unchanged. The filter can be flipped in and out between the eyepi^ and eye, making the nebula appear to blink compared to the stars.

Most of the many variable stars in Sagitta are faint, but S Sagittae is an inter esting object for observation with binoculars. It is of the Cepheid type, varvi between the visual magnitude limits 5.3 and 6.1 in an cight-day period.

Before leaving this rich area, double-star observers with small telescopes will want to view Zeta (Q Sagittae, an easy pair of 5th- and 9th-magnitude stars sep arated by 8". (The brighter component is a very close binary, beyond the reach of amateur instruments.) Theta (0) Sagittae is another easy double, magnitudes 6 and 9, separation 12".

Unraveling the Helix

One of Scotty's greatest and most respected traits was that he did not write to promote himself but to report on the progress of amateur astronomy. He made it his job to involve amateurs in that revolution; of course, he was often the one to get a fire going. Scotty was probably most satisfied when he received reports from amateurs who wanted to share their opinions on a particular subject of controversy. One great example of how Scotty promoted this sharing of knowledge can be found in his articles on the Helix Nebula in Aquarius. The Helix is a tough celestial nut to crack. Its pale hazy disk is often missed by amateurs who are accustomed to seeking much smaller objects. For advice, he would say, "Averted vision is needed, and the eyepiece field should be at least '/2⁰ in order to surround the nebula with some contrasting dark sky." As you will see here, readers of Deep-Sky Wonders had widely varied opinions on the object's visibility, and Scotty respected each and every one of them. His column was a forum for the amateur's voice to be heard.

The planetary nebula NGC 7293, also known as the Helix Nebula (Figure

10.7), lies in Aquarius about a third of the way from Upsilon (v) Aquarii to 47. It has a total magnitude of about 6, but its large apparent diameter — nearly half that of the Moon — spreads the light out and makes it a difficult object visually. Tire Herschels overlooked this nebula with their large reflectors. It is best to view this planetary with a rich-field telescope. With exceptional skies, an experienced eye will sometimes see traces of the nebular structure so vivi .

recorded in photographs.

I recently saw the Helix Nebula with the 4-inch Clark refractor, and was ce tain that it was glimpsed in a 2-inch finder. Burnham notes in his ^^ee Handbook that it can be spied in binoculars. Years ago I suggested that rea

_ntj me their observations of the Helix Nebula, which I sometimes call the •‘Sunflower.” Over 200 letters were received, giving a good idea of its visibility in _niany instruments and at a variety of magnifications.

Harry Cochran of Brentwood,Texas, found the Helix difficult in a 12'/?-inch at (,7X though the view was better at 117x. On the other hand, to Leonard P. Farrar of Rialto, California, the planetary appeared much like its photograph. He used _a 10-inch mirror by Alika Herring in a mountain sky so clear that a flashlight beam was invisible.

Small telescopes in relatively poor skies seldom revealed color. Ted Komorowski told of a gray disk easily visible in his 8-inch f/7.5 at 56x. Yet Ray Lima of Jacksonville, Florida, readily saw blue-green in his telescope of the same aperture. When an object is near the visual threshold, color is not usually seen, only gray- To obtain maximum color perception, use the lowest magnification available.

The nebula's central hole was sighted by only a few observers, who included Michael Pleinis, Aberdeen, South Dakota (4- and 6-inch telescopes), and Mark

Figure 10.7

The Helix Nebula is the planetary nebula nearest to our Sun. At 15' in apparent diameter, it is also the largest.

Grunwald, Mishawaka, Indiana. Among others, Tom Burton of Santa Cruz, California, and N. Taylor in New Zealand could not see the central hole. Taylor ⁿ°ted that at higher powers NGC 7293 filled the field and details were lost.

The performance of instruments similar to Moonwatch Apogee telescopes ^varied. James H. McMahon, China Lake, California, glimpsed NGC 7293 at the J’rnit of visibility, after he had failed to see it a year before. Buddy Tempest, Columbus, Indiana, found it without using averted vision, while William O’Brian °f Gary, Indiana, easily saw the planetary at 16x and 25x, though it was invisible 7 x 50 binoculars.

The bulk of my correspondents indicated that thc Helix was more readily _See in binoculars and finders than in telescopes. Yet some observers, such as Bj]| Perkins of South Boston, Virginia, had the opposite experience.

A few amateurs compared the Helix with familiar objects. For example Fr_e Lossing of Ottawa, Canada, thought the binocular appearance of NGC 7293 \ similar to that of M33 in his 8-inch. Jan Finkelstein, Brooklyn, New York saw ^S resemblance to M57 in his 2.4-inch refractor.

Atmospheric clarity obviously played a major role for seekers of the Helix Observers on mountains did much better than smog fighters, though the latte had easier viewing than one would have anticipated from Hans Vehrenberg’s statement in his Atlas of Deep-Sky Splendors: “Even on dark and extremely clear nights it is barely distinguishable as a very faint patch.”

Grunwald’s excellent results came after a cold front had just passed, making the sky so clear that M33 was visible to the unaided eye. Such favorable conditions should always prompt searches for the toughest deep-sky objects.

Most observers agreed that NGC 7293 was captivating. Edward Stockton of Lithia, Florida, recalled: “It was so faint that it seemed like a figment of the imagination, but its shape was unmistakable.”

In 1983 I again asked for observers' comments on the Helix Nebula, and a number of people replied.

Jim Meketa of Newton Center, Massachusetts, easily viewed the Helix with 7 x 35 binoculars. (Binocular vision often shows a fainter object than could be detected in a view with one eye alone. You can experiment by viewing a faint object with binoculars and covering one of the objectives. Chances are the object will disappear from the field.) Meketa’s binoculars showed the Helix as a “small ghostly doughnut,” but a 4'Z-inch finder on his 18-inch reflector showed some detail. The ring appeared unbroken, and there was an “unmistakable" tenuous glow inside it. There was no hint of the helical structure seen on photographs that give rise to the nebula’s popular name. Meketa believes that the Helix might be seen with the naked eye under excellent conditions.

In Georgia, David Riddle observed NGC 7293 with a wide range of instruments. It was “visible" in a 6 x 30 finder and “easy” with 8 x 40 binoculars. The central star was seen with a 6-inch f/4 Newtonian, and his best view came with an 8-inch f/6 reflector at 80x.

From Riverside, California, Stephan Karnes could not see the Helix with a 14-inch reflector until a nebula filter was added to the eyepiece to cut down the urban light pollution. Like Meketa. he noted faint nebulosity filling ⁽h^e center of the ring. Another Californian, Steve Gottlieb of El Cerrito, had trouble viewing the Helix with a 13-inch reflector at his home, while it was seen easily from high in the Sierras with a 6 x 30 finder and nebula filter. His con elusion is that thc visibility of the Helix is controlled more by sky conditions than telescope size.

One of the best reports came from Joanne Konst of Kenton, Ohio: ‘ N 7293, the Helix Nebula, is invisible without a UHC filter,” she writes. "But wit the filter 1 see a round glow about 15' across, and a dark center is obvious. Three _stars are seen against the nebulosity, but otherwise there is no detail."

A"Field Day" in the South

Occasionally a great celestial event forces masses of Northern Hemisphere observers to pack their gear and head south. Take, for instance, the 1986 return of Halley's Comet. Countless droves of amateurs armed with telescopes of various sizes descended upon the less populated regions of the south — the outback of Australia, the Alps _of New Zealand, or South America's barren Altiplano — simply to glimpse a part of astronomical history. But Scotty knew that these pilgrimages could yield even greater prizes. "The comet is going to have an effect on deep-sky observing," he predicted. "Flocks of amateurs are planning trips to the Southern Hemisphere, where many will have their first encounters with the glories of the southern sky ... I wouldn't be surprised if observers spend more time exploring the southern heavens than looking at the comet." And he was right. What he wanted to remind us, however, was that many celestial sights in the southern sky can be seen from northern locations. Here are a few of them that Scotty wanted readers to enjoy. Their declinations, he reminded us, are no farther south than that of the Scorpion's tail.

One of the great treasures of life is heaven’s starry vault on a clear night, when the familiar constellations blaze forth in mystical glory. It’s an extra treat if the sky is clear right down to the horizon and we can explore regions normally lost in thc haze.

In theory, everyone living south of the 45th parallel can see to the very bottom of Sagittarius. So they can try to hunt out four spiral galaxies in the constellation’s southeast corner; their presence was brought to my attention several years ago by New York amateur and author Phil Harrington. All arc plotted on Sky Atlas 2000.0, and Harrington remarks that they are “challenging finds for even the most accomplished deep-sky observer.”

Although they have eluded me from Connecticut, I saw them dimly with a 4-•nch rich-field reflector in the Arizona desert. Farther south at Puerto Escondito, Mexico, they were bright and easy in the same telescope. All are between 1' and 2' in diameter. The most obvious member of the group is 12th-magnitude NGC 6902, which shows some detail in a 10-inch aperture.

If these are too far south for your observing site, but you can see brilliant Fornalhaut in Piscis Austrinus, then try looking for another worthwhile quartet °f galaxies (Figure 10.8). NGC 7172 and the tightly bunched NGC 7173-74 and 2176 are visible in my 4-inch Clark refractor from here in Connecticut. They’re ^all about 12th magnitude, and plotted on Sky Atlas 2000.0. NGC 7172 is 2' across, but the other three are only half as large. John Herschel chanced upon them ^while sweeping the sky from the Southern Hemisphere. When he published a general catalog of deep-sky objects in the mid-1860s, over 90 percent of its 5,000-

Figure 10.8 if you can see Fomalhaut, you can find the galaxies NGC 7172, 7173, 7174, and 7176, which are clustered about 12° to the west.

plus objects were those discovered by him and his father William, and nearly 100 of the exceptions were from Messier’s famous list. Observers in the Americas had little to contribute.

After the U. S. Civil War, however, Americans went on an observatory-building binge. Funding for many installations came from state legislatures, since the astronomers provided time signals to their local areas. Almost every observatory from that era had a transit instrument for determining time. In return for this service the lawmakers funded a large telescope to keep the astronomers happy. When I was at the University of Wisconsin in the 1930s, Washburn Observatory still had the big brass fittings on the control board that routed time signals to commercial customers.

Most American observatories did not have special programs to search for deep-sky objects. Nevertheless, astronomers found new nebulae in the course of other work and published short lists of these accidentally discovered objects. By the time J. L. E. Dreyer compiled the NGC in 1888, the list had grown to nearly 8,000 objects.

About two dozen of these were discovered by Edward S. Holden with the 15'/’-inch reflector at Washburn Observatory in Wisconsin. One of them. NGC 6912, lies less than 1° west of Omicron (o) Capricorni. When Holden canu-across it on August 17,1881, he noted it as very faint. I still look at it when I get a chance — after all. there weren’t many deep-sky objects discovered in the state where I grew up.

Figure 10.9 The globular cluster M30 lies about 40,000 light-years away in the constellation Capricornus. It is best viewed with larger telescopes.

About 20° east-southeast of NGC 6912 is the globular cluster M30 (Figure 10.9), which Messier discovered in 1764. Although he saw it as a round nebula without stars, William Herschel resolved it into a “brilliant cluster” two decades later. About 8th magnitude and a bit over 10' in diameter, M30 is not one of the great globulars. Its bright center and easily resolved edges do, however, make it an interesting object for small telescopes. I find this sight rewarding in a 4-inch scope at 40x.

M30 can be a frustrating object for amateurs attempting a Messier marathon in March or April. Because of its position relative to that of the Sun, the cluster is almost impossible to find in either the evening or the morning sky, spoiling the chance to view all the Messier objects during a single night.

Sweeping northward from M30 into Aquarius brings us to several interesting objects. M72 is a globular both smaller and fainter than M30. In the 1930s I viewed it with the 13-inch reflector that belonged to the Milwaukee Astronomical Society and remember the edges of the cluster being well resolved.

Just east of M72 is a tiny group of four stars that Messier perceived as a dim glow and therefore included as entry 73 in his catalog. Some observers continue ^to debate whether this group belongs on the list with the French comet hunter’s °ther discoveries, but there is no doubt about its correct identity.

Only 2° northeast of M73 is a distinguished planetary nebula that Messier overlooked even though it was certainly within range of his telescopes. NGC ?0()9 is perhaps better known as the Saturn Nebula (Figure 10.10). The name

Figure 10.10 Nicknamed the Saturn Nebula because of its appearance in larger telescopes, NGC 7009 is one of the brightest planetary nebulae in the sky.

comes from Lord Rosse, who first saw two faint ansae extending from the central nebulosity, but the object itself was discovered by the elder Herschel. What is the smallest telescope that will show the planetary’s faint extensions? The nebula’s central star is about magnitude 11.5. It stands out like a beacon in my eye that had its lens removed in a cataract operation several years ago and is now sensitive to ultraviolet light.

In the Pasture of Grus

Now we II have a field day in the sky below Fomalhaut, the brilliant lst-mag-nitude beacon in Piscis Austrinus. I like to think of this region as the pasture of Grus the Crane, the remarkably birdlike star group to Fomalhaut’s south. A number of galaxies here, while challenging objects from mid-northern latitudes because of their low altitude, are no farther down than the lowest stars in Scorpius’s tail.

IC 5271 is a spiral galaxy forming a neat little triangle with the 4th-magnitude stars Delta (8) and Gamma (y) Piscis Austrini. It is about 2' long and half as wide, large enough to be identified at 50x (though lOOx would be a better magnification with which to search for it). At magnitude 12.6 it can be seen in a 4-inch telescope when well above the horizon. Once, while in Mexico’s Sonora desert. I tracked it down with a 4-inch rich-field reflector at 40x. The sky was very good that night, and the naked-eye limit for stars was about magnitude 7.4. (It's always a good idea to note the naked-eye limit in your logbook, since I find this a much better indicator of sky transparency than the usual 1 -to-10 scale.)

A little over 2° south of IC 5271 is the similar-looking spiral galaxy IC 5269. The second Index Catalogue of Nebulae (which contains objects found between |g95 and 1907) lists it as very faint, pretty small, and round, to which I can reply, “No Y^es’^and somewhat.” IC 5269 is also the northernmost of five galaxies forming ^{a sma}" ^curv*ⁿg chain. It is easy to locate since it lies just west of the center _of a small triangle of naked-eye stars.

yiie two stars marking the base of this triangle are on the border of Grus. Almost on a line between them is IC 1459, an elliptical galaxy I estimate to be magnitude 10.0. Roughly '/2⁰ farther south is NGC 7418, discovered by John Herschel from Africa’s Cape of Good Hope. It’s a fat 3' in diameter and magnitude 11 -4- My 4-inch reflector gave a good view of it in the clear desert air.

The next galaxy in the chain is NGC 7421, which lies !6° almost due south of NGC 7418. It is about 12th magnitude. Another 14° to the southeast is IC 5273. Although about half a magnitude brighter than NGC 7418, it was missed by the observers whose discoveries were published in 1888 and is listed in the second Index Catalogue.

Star-hop to these galaxies by starting at Fomalhaut, moving to Delta (8) and Gamma (y) Piscis Austrini, and then to the small triangle of stars. This is a simple task — if the telescope and finder show the same sky orientation. On many commercial telescopes either the finder or the main instrument comes equipped with a star diagonal, which gives a mirror image of the sky. Trying to match this view with a star chart is like reading a newspaper in a mirror.

One solution is to use an Amici prism in place of the diagonal’s mirror or right-angle prism. Amici prisms combine the comfort of using a diagonal with a correct-reading image of the sky that can easily be matched to a chart. They are becoming increasingly scarce on the surplus market, but if you can find one I certainly recommend getting it.

A nice group of four galaxies forms a rough square straddling the -40° declination line on Sky Atlas 2000.0. While I don’t usually receive amateur reports of objects this far south, California observer Tokuo Nakamoto has seen at least two of them.

NGC 7410 is an obvious cigar-shaped galaxy at the northwest corner of the square. It is about 5' long and 2' wide. With the 4-inch reflector I estimated it as magnitude 10.0. Using a 6-inch f/8 reflector, Nakamoto found it brighter toward the center with a starlike nucleus. Much fainter is 12.7-magnitude NGC 7462 at ^[he square’s southeast comer. It is another thin spindle of light, about 3' long. Nakamoto noted that it has no apparent nucleus.

At the southwest corner, NGC 7424 is about 7' in diameter, nearly round, and 10-2 magnitude. At the northeast corner is NGC 7456, some 6' long, 2' wide, and magnitude 11.9. Can anyone confirm whether it has a stellar nucleus?

Before leaving this region of the sky, try for a tight group of four galaxies all ^Vlsible in the same telescope field 5° southeast of the square. Three of them are nice big spirals, all apparently barred, cavorting in a group like white beluga "'hales. The fourth is just to their west, off by itself. This is NGC 7552, listed as

visual magnitude 10.7 and 3' across.'rhe western galaxy of the triplet, NGC 75^ is cataloged as magnitude 10.6, but it seems to outshine NGC 7552 by even ino_rc than the official 0.1-magnitude difference. NGC 7590, about a magnitude fainter is somewhat smaller than its neighbors. Of similar brightness to NGC 7590 ■ NGC 7599, though it is nearly as large as NGC 7582. I once marveled at these galaxies from the flanks of a smoking volcano in Guatemala.

OCTOBER OBJECTS

OCTOBER OBJECTS (CONTINUED)

Ast = Asterism; BN = Bright Nebulo; CGx = (luster of Goloxies; DN = Dork Nebulo; GC = Globulor Cluster; Gx = Goloxy; OC = Open Cluster; PN = Planelory Nebulo; ♦ = Stor; ♦ ♦ = Double/Mulliple Star; Var = Vorioble Slor__________ \