Watching from a Distant Earth the Dreaded Arachnid that Felled the Great Hunter
From: firstname.lastname@example.org (Clay Sherrod)
This eighth Constellation Guide, "GO TO SCORPIUS" of the series "GO TO GUIDES for the ETX and LX 90 Telescope Users" takes us into the realm of the beautiful Milky Way galaxy as we peer very near the actual galactic center and marvel at the array of wonderful deep sky objects, dense clouds of gravitationally-bound stars, dark obscuring and light-absorbing space dust and wonders beyond imagination. Although we have explored many "globular clusters" in previous constellation "GO TO" GUIDES, and these discussed in detail in "Observing Globular Clusters" (http://www.weasner.com/etx/ref_guides/globulars.html) , the constellation of Scorpius provides us with TWO of the most interesting and CONTRASTING globulars of all, Messier 4 and Messier 80, both outstanding objects but strikingly different from one-another. In addition, you will be adding to your USER OBJECT library on AutoStar the sky's most intense X-ray source from deep space! This is quite a gem to show and tell at the next star party!
You will begin your "GO TO" journey into Scorpius via the bright star "Antares", a vividly reddish star that has been known as the "Rival of Mars," and indeed the two are frequently very close to one another, not just in brightness and their blood red colors, but also as we see them in space. The ECLIPTIC (the zone of twelve Zodiacal constellations through which all the planets, moon and sun appear to move from Earth) passes through Scorpius, and hence Mars frequently "visits" its rival - the heart of the scorpion.
These and other fascinating objects of Scorpius will be discussed following - first in a concise list with exact coordinates and magnitudes and then individually - with specific details of what YOUR SCOPE.....the ETX 60, 70, 90, 125 or the LX 90....can expect to show you....and what you can expect to NOT see. So many times casual observers are disappointed when they attempt to find an object beyond their telescope's capability....or perhaps let down from what the photographs of the great observatory telescopes have shown them in the textbooks, magazines and advertisements. Using our "GO TO" GUIDE allows you to know right off what you can expect to see of each object.
Each GO TO object is discussed for your telescope regarding the type of conditions necessary for you to view it optimally for discern the very faintest details....double star challenges for each size telescope .....magnifications and aperture necessary for most objects, and much, much more. This is YOUR complete GUIDE to pique you curiosity to further explore the stinging scorpion of space. Use these guides as an excellent reference for your next star party itinerary, or a beginning for further study into the thousands of objects visible in this part of the sky.
Truly, as reports continue to come in on these extensive Constellation Study Guides, they will most definitely put your AutoStar to work for you in the most efficient and enjoyable way possible!
We hope you enjoy these comprehensive GUIDES to touring the constellations via your AutoStar and its computer-driven telescope. Each new installment will appear frequently, complete with diagrams, charts and illustrations that you will find nowhere else. Please let us hear YOUR feedback and your observations of each and every constellation after YOU have toured its vast reaches of our skies!
The constellation SCORPIUS (pronounced "SKOR-pee-us") is one of the few constellations that nearly all who see its outline (even novice skygazers and the general public) immediately accept the fact that its stars do, indeed, trace a very good likeness of a celestial scorpion. The constellation is HUGE and its bright stars and wonderful celestial objects are positioned toward our line of sight into the center of our spiral galaxy, the "Milky Way." Hence, there is a plethora of wonderful and easy deep sky targets.....so many that I was forced to work my way down from 52 selected objects to "only" 20.....the largest selection of any "GO TO" GUIDE thus far. But once you begin exploring within the boundaries of this magnificent constellation, you will quickly realize that "20 objects" simply does NOT do this chunk of sky justice!
Dominant in the earliest Greek and Roman mythology, and sanctified through writings and art, is the legend of the mighty and monstrous scorpion and the seemingly immortal and invincible giant among "heroes", Orion, of winter sky fame. In fact, you might note at this point that Scorpius is almost EXACTLY in the opposite side of the sky from Orion! A mere curiosity? Not if you were an ancient Greek or Roman writer...
First, I must mention that even Greek writers and poets have their disagreements, and their legends and lore of the starry sky are no exception. One more colorful and perhaps heart-warming stories concerning the great scorpion is that of the young Greek Phaeton. In his braggingly boyish fashion, arrogant and ego-driven, this young man chose imminent death by leading his stead-driven chariot into the burning sun. Only, right before the sure-fateful encounter, Phaeton's horses which drew the mighty chariot were surprised and frightened by a huge scorpion that arose in the sky and diverted their paths away from the sun. For the valiant and saving effort, the mighty scorpion was placed prominently in the sky, signifying the place where the sun would have been on the day of Phaeton's suicidal journey. So in this heart-warming (pun intended) story, the Scorpion was our hero....saving a handsome young lad (not to mention the horses) from certain death.
But in the earliest Greek mythology and most embedded, is the tale that casts the dreaded scorpion in a much different....darker....light. For it was the great arachnid and his poisonous and feared sting that brought to his knees Orion, the Mighty Hunter and Hero of our nighttime winter skies. Orion was invincible, or seemingly so, until it was revealed by his adversaries that he had one weakness: a soft patch of exposed skin behind his sandal by the Achilles tendon. So, after surviving battle after battle and defeating celestial monsters and evil by the dozens, Orion was caught quite off guard one evening after defeating the "bad guys" as the scorpion sneaked up behind him...and, yep: stung him right there. After much pain and suffering, Orion finally succumbed to the sting and the gods placed him fittingly among the stars.....exactly OPPOSITE the Scorpion that killed him. So the parade and chase continues today....Orion half-way across the sky in pursuit of villains to subdue while the mighty Scorpius engages in a chase that NEVER gets it any closer than it has always been to Orion. Once bitten is enough......
The ancient skywatches of Persia and Arabia, from whom we thankfully have been given most of the colorful names and legends of the stars and constellations, also saw a scorpion in Scorpius. It would seem that the dreaded scorpion would be quite familiar feature of the baked middle eastern lands. The oldest such connotation by the Persians is "Girtab", which translated literally means "the stinging one." It is interesting to remember that the constellation of Libra, to the west of Scorpius, was once associated with this Scorpion of the Sky, with the now-Libra stars of ZUBEN EL GENUBI ("the southern claw") and ZUBEN EL SCHEMALI ("the northern claw") being the lower and upper, respectively, "pinchers" of the scorpion.
In Babylonian and earliest Mesopotamian lore, the constellation was also configured as "almost" a scorpion, but with a torso of a human being. Tombs and ritualistic material from very early Egypt also recognizes the scorpion, particularly through the legend of Horus who was slain by a scorpion, but nurtured back to life by his mother, Osiris, who used the magic of the gods for revival and protection. Hence, this SAME myth still persists today in Egypt and surrounding lands as homes, temples, buildings and even cross-country journeys are "protected" from the same magic through inscribed images that are displayed as emblems of immunity to bad fate.
Only in China did our earliest skywatchers NOT designate a scorpion to this clearly-defined outline; rather they saw it as "the dragon who devours the sun," surely a reference to perhaps a solar eclipse that must have occurred at one time in that constellation, during which the sun seemed to suddenly vanish (eaten, of course by the dragon) and then only to reappear! (regurgitated...apparently it did not agree with his delicate digestive system). Later, this famed dragon became known as the "Azure Dragon" and still persists today, as a kind and good spirit that is rising from the Celestial River (the Milky Way - see "GO TO" Draco) as he prepares to come to Earth with his blessings. It is strongly believed that this myth from the East somehow made its way thousands of miles across the oceans and influenced the pre-Colombian Toltec people of now-Mexico in the creation of THEIR myth of 'QUESTZACOATL' a half-man/half-scorpion legend that is remarkably similar to the Chinese Azure Dragon.
YOUR SCORPIUS CONCISE DIRECTORY OF OBJECTS -
This mighty constellation is so rich in beautiful objects, stars, clusters, nebulae - from naked eye, to wide field, to telescopic - that is was very difficult to select (and limit) the number of objects for our "GO TO" TOUR.
I have chosen the finest 20 objects in Scorpius to showcase for your "GO TO" TOUR; in this case, all objects listed below will be visible in all telescopes (some naked eye) from the ETX 60 through the LX 90; of course larger apertures may "show" an object a bit closer and "better," but frequently a wide field and low power view is more desirable than aperture. This is the case for MANY of these objects in Scorpius since it is embedded in the very star-cloud-rich areas of our Milky Way galaxy. Indeed, I strongly encourage your to step away from the telescope often and scan the beautiful open skies and star fields of the Scorpius-Sagittarius regions with a good pair of 7 x 50 or 10 x 50 binoculars. It is truly like taking a trip into space, with one brilliant star-filled cluster after another. Even the binoculars will show dozens of deep sky objects that are not visible to large telescopes in other areas of the sky.
The constellation's very low declination for observers in the northern hemisphere make it difficult for observations in latitudes higher than 40 degrees north; so when the skies are crisp and dark and you can "see all the way to the horizon" on those rare nights....don't let it go by: LOOK at Scorpius! Conversely, our observers south of the equator are blessed with favorable near-overhead views of this constellation and the brilliant clouds of the Milky Way nearby.
As with all of the "GO TO" TOUR constellation lists, I recommend a good star atlas and/or chart which will list all the finest objects, constellation-by-constellation. One very handy reference guide is the PETERSON FIELD GUIDE TO THE STARS AND PLANETS, which features complete lists with declinations, right ascensions, magnitudes, and all pertinent information for you to expand your observing horizons beyond this brief GUIDE.
Note that your AutoStar will NOT have every object listed on every constellation GO TO tour....this is intentional. You can access some of the most interesting objects of the sky directly from their coordinates. It is quite simple as you merely enter these coordinates as follows in the 10-step process:
1) Press the "MODE" key and hold down for 3 seconds and release;
2) Displayed will be the current Right Ascension and Declination of the center of field of view of where your telescope is presently pointed (assuming that you have properly aligned from "home position");
3) [NOTE: if you have the Meade electric focuser attached to any of the ETX or LX telescopes, holding down the "MODE" key will bring up the "Focus" command first....merely scroll (lower right scroll key) down one step to access the RA and DEC to enter your desired coordinates]
4) Press the "GO TO" button on AutoStar;
5) This will change the display and you will note the cursor blinking over the first digit of RIGHT ASCENSION (R.A.); merely use the number keys and dial in the R.A. of the object you are searching for;
6) When done, press "Enter;"
7) This moves the blinking cursor over the "DEC" coordinates;
8) [NOTE: the declination, unlike R.A., can be either positive or negative and you will see the "+" or "-" sign displayed depending on where your telescope is aimed at that time; if it is NOT the desired setting (plus or minus), merely use your arrow key to move the blinking cursor OVER the "+" or "-" sign and change by using either of your lower corner SCROLL KEYS;
9) Proceed to enter the DEC using number keys;
10) Press either "Enter" or "Go To" when finished and the telescope begins slewing to your desired object!!
The constellation tour Star Chart above (click on and save to a file on your PC; then open it and re-size to fit the page and print for a very handy at-the-scope star chart) will get you started on your journey for this constellation.
Following is the complete 20-object list for your "GO TO" TOUR of Scorpius; you may wish to find the majority of the objects from the AutoStar Library (for example, you can easily pull up "Object/Deep Sky/Messier Object/..type in '80'...." and then press "Enter", followed by "GO TO" to access my favorite all time globular cluster. On the other hand, if you want to experiment and become a "better AutoStar user" try entering the exact R.A. and DEC coordinates of that object as described above after holding down the MODE key. You will find the accuracy of entered GO TO's to be somewhat less than those stored in AutoStar, but the capability of acquiring unlisted objects is fantastic!
OBJECT 1: very bright star - Antares (alpha Scorpii) - R.A. 16h 26' / DEC (-)26 19 - Magnitude: 0.92, brilliant red OBJECT 2: fine bright double - Akrab or Graffias (beta Scorpii) - R.A. 16h 03' / DEC (-)19 40 - Mags: 2.6 & 4.9 OBJECT 3: what gives?? - Dschubba (delta Scorpii) - R.A. 15h 57' / DEC (-)22 29 - Magnitude: variable, mini-nova? OBJECT 4: nice wide double - Zeta Scorpii (sometimes "Grafias") - R.A. 16h 51' / (-)42 17 - Magnitudes 3.6 & 4.8 OBJECT 5: wide nice double - Mu Scorpii - R.A. 16h 49' / DEC (-)37 58 - Magnitudes: 3.1 & 3.6 naked eye! OBJECT 6: QUAD star - Nu Scorpii - R.A.16h 09' / DEC (-)19 21 - four stars, two close pairs. OBJECT 7: tough LX 90 test double - XI Scorpii - R.A. 16h 02' / DEC (-)11 14 - Magnitudes: 4.8 & 5.1(tough!) OBJECT 8: tough ETX 90 test double - Al Niyat (sigma Scorpii) - R.A. 16h 18' / DEC (-)25 29 - Mags: 2.8 & 9 OBJECT 9: classic variable star - RR Scorpii - R.A. 16h 53' / DEC (-)30 30 - Magnitude: 5.4 to 11.7, 280 days OBJECT 10: strongest X-ray source!! - Scorpius X-1 - R.A. 16h 17' / DEC (-)15 31 - Magnitude: 13 OBJECT 11: fine globular cluster - Messier 4 (ngc6121) - R.A. 16h 21' / DEC (-)26 24 - Magnitude: 7.4 (a must-see) OBJECT 12: galactic star cluster - Messier 6 (ngc6405) - R.A. 17h 37' / DEC (-)32 11 - "Butterfly Cluster" OBJECT 13: nice star cluster - Messier 7 (ngc6475) - R.A. 17 51' / DEC (-)34 48 - large and bright! OBJECT 14: fine globular cluster (in Ophiuchus) - Messier 9 (ngc6333) - R.A. 17h 16' / DEC (-)18 28 - Magnitude: 8.5 OBJECT 15: tiny globular cluster - Messier 64 (ngc6266) - R.A. 16 58' / DEC (-)30 03 - very compact, bright center! OBJECT 16: best globular cluster - Messier 80 (ngc6093) - R.A. 16h 14' / DEC (-)22 52 - very tight - compare to M-4! OBJECT 17: diffuse nebula - ngc6302 - R.A. 17h 11' / DEC (-)37 03 - Magnitude: 10 (a must-see: the "bug nebula") OBJECT 18: galactic cluster - ngc6231 - R.A. 16h 51' / DEC (-)41 43 - magnificent brilliant white cluster! (a must-see) OBJECT 19: very nice cluster - ngc6242 - R.A. 16h 52' / DEC (-)39 25 - Magnitude: 8.8, same field as ngc6231! OBJECT 20: distant globular cluster - ngc6388 - R.A. 17h 33' / DEC (-)44 43 - nice, bright, very small!
A VISUAL GUIDE TO OUR DEEP SKY OBJECTS IN SCORPIUS -
Object 1 - Very Bright Star ANTARES (Alpha Scorpii)
Only the "red drop of winter" - Betelgeuse - is more scarlet than the brilliant reddish Antares. From the Greek to mean "the one who rivals Mars", this reference eludes to the deep red color and brightness that is nearly an exact match for the Red Planet when at its closest (perihelic) opposition....which the best always take place in summer months and frequently VERY near Antares. The opposition of Mars in 2001 is no exception when both stood near one-another as a shining red pair.
Both Betegeuse and Antares are perhaps the largest stars of our Milky Way (that we know of); although Betelgeuse is a bit large, Antares boasts a diameter.....get this: 600 MILLION MILES ACROSS! That compares to our sun at slightly less than one million miles diameter. There is a faint (magnitude 9)companion star to Antares that is a full 3" arc nearly due west of the bright star; even though this may SEEM easy in the ETX 90 and larger scopes it clearly is not because of the brilliance of the main star. With the ETX 125 and LX 90, you MAY be able to glimpse this fainter, overshadowed star under high magnification, about 250x to 300x.
In wide field telescopes, such as the ETX 60 and 70, compare the color of Antares to nearby stars of spring and summer, notably VEGA (clearly blue-white), DENEB (definitely yellowish), as well as ALTAIR (orange-yellow).
Object 2 - A Fine Double Star "Akrab" or "Graffias" (Beta Scorpii)....a very good double star for smaller telescopes!
The latter name "Graffias" is from the Greek and sometimes associated with ZETA Scorpii, so some confusion exists in the actual name. It is interesting, however that "Graffias" signifies the "star of the crab," a creature that was not clearly distinguished from the Scorpion in ancient Greece. At magnitude 2.5, Beta has a nice bright companion star magnitude 4.9 about NNE from the star a full 14" arc seconds distant. It makes a wonderful pair at very low power, even with the wide field ETX 60. Using MEDIUM magnifications in all telescopes, look for the wonderful color contrast of these two stars. The brighter star has always looked distinctly yellow to me on a steady night, with the fainter star seeming blue-green. Most observers see pretty much the same contrast, although some eyes see more blue or more green in the secondary star.
Object 3 - Delta Scorpii - "Dschubba" - What a ride this star is taking us on!
Normally this is nothing more of interest than a somewhat variable star that is also fairly bright and comprises the "head" of the scorpion. However, beginning fittingly at the start of the 21st century, Dschubba erupted almost "nova style" from its normal 2.3 magnitude to attain a brightness that continues to persist at almost the same magnitude as Alpha....Antares! Dschubba is an "early "B"-type star, so this type of minor nova activity is unusual for such a high-energy star. Photographs show some nebulosity coming from this star and possibly "connecting" to other stars nearby, indicating the possibility of similar outbursts in the past. This is a star that CERTAINLY bears watching. You can compare magnitudes easily with nearby bright stars with the naked eye. Look for any color changes using very low magnifications in your telescopes.
Object 4 - Zeta Scorpii - also known as "Grafias" (note only one "f" in this duplicated star name)
I have included this star because it is a very wide and fine optical double star for low power, wide field telescopes and thus very fitting for the ETX 60 and 70. It can be enjoyed even in a pair of binoculars, but the wide field telescopes provide one of the most striking star fields against these two stars imaginable. The two stars, magnitudes 3.8 and 4.2 are a full 7" arc apart in an almost exact east-to-west orientation. These stars are NOT a true double, only appear to be optically from our vantage point here on Earth.
OBJECT 5 - Nice very wide Double Star; great wide field views of the sky! Historical Interest!
This is a beautiful field in the middle of the rich summer Milky Way! The double is made of two very wide stars, about 6 minutes (') arc (not seconds - ") , the brighter of the pair being about magnitude 3.1. Mu Scorpii is referred to in Polynesian cultures as two children who are bound together in faith in spite of abusive and tormenting parents. Be sure and scan the wide-field sky at your lowest magnification and try to spot ngc 6281 and ngc 6242, both very fine galactic star clusters located in the "Sagittarius Arm" of our galaxy.
Object 6 - A Neat Quadruple Star - Nu Scorpii
Although this is not quite as outstanding nor famous, this is much like the well-known "Double Double Star" of Lyra (see http://weasner.com/etx for the complete Constellation Guide for Lyra). This is an interesting low power field in itself, with this complex star system on 1.5 degree east of Beta Scorpii (see chart). The first pair (denoted "A" and "C" stars, magnitudes 4.0 and 6.2) is separated from one-another almost the girth of the planet Jupiter seen in the same eyepiece, so it is easily resolvable with all telescopes; look for the orientation nearly NNE to SSW. Begin to raise the power on your telescope on the FAINTER of the two stars ("C") until you split it into two more stars (its companion is "D", magnitude about 7.7). This might be difficult for the ETX 60 and 70, but should be relatively easy in the ETX 90 and larger scopes. They are well separated in my ETX 125 at 227x. NOW, using the ETX 125 the LX 90 and medium high (about 227x) power, look carefully at star "A" which should resolve into a VERY close but clearly definable two stars, magnitude 4.6 and 5.6. The companion to star "A" is designated as "B". I would be very interested, particularly from ETX 90 users, to find out the difficulty or the ability to split star "A" into its two components.
Object 7 - A true test for the LX 90 - Double Star XI Scorpii
Perhaps this star is asking "too much" from the fine LX 90 8" aperture. However....it can be done, even if only partially. This very, very close 4.2 magnitude star CAN be resolved at high (i.e., 300x and above) power. Look very carefully and very close to the brighter star at this magnification to the NORTHWEST and touching the main star. If nothing else, the resolution of the large 8" should allow for the star to be at least "elongated" in a NW-SE direction, indicating that the Airy Disks are attempting to be resolved. Use a very steady night; anything less and you are wasting your time. If you can split this star, and you are SURE that you have zeroed in on the correct star, I would like to hear of your observations. At separation only 0.6" arc or less at the present time, there is no reason to even try with smaller apertures.
Object 8 - Very Nice Double - Al Niyat (sigma Scorpii)
This star signifies the hard crusty exoskeleton of the rugged scorpion, the panel directly covering his heart, as the name implies "heart shield." This star is magnitude 2.9, very bright in the telescope, and exhibits a very faint companion a fair distance (20" arc, about half the diameter of Jupiter in the same eyepiece), almost DUE WEST of the brighter star. This white (brighter star) and blue pair is a challenge for the ETX 90 because of the brightness of the main star; if it were not for that it could be seen in the ETX 60 and 70, but that would be a very tough challenge. It is relatively easy in the ETX 125 and the LX 90 at moderate (about 150x) power. NOTE: one of my favorite all-time globular clusters, Messier 4 (see below) is located within only one degree SE of this star; user your finder to locate the cluster.
Object 9 - A Classic Variable Star: RR Scorpii - An ideal variable star for all telescopes!
RR Scorpii is a classic "Mira-type" variable star which actually grows in diameter to cause its seen brightness increases; as it subsequently shrinks back down in size we see a diminishing brightness here on Earth. That total cycle takes the star from naked eye brightness (!!) of 5.2 all the way down to telescopic-only brightness of about 11.5. Even at that low brightness, the ETX 70 can easily keep up with the entire cycle on a very dark nights. Only 1 degree WSW from Messier 64, a bright globular cluster, this is an easy star to find your first time out. To aid in locating - and more importantly ESTIMATING using selected comparison stars - click on the link below to the American Association of Variable Star Observers and download to a file the accompanying chart; save it to file, click on it to open the file, resize to fit your page and then print out....other charts are also available for comparing when the star is very bright ("a" charts, wide field for acquiring brighter stars) and very dim ("c" chart for when the star is dimmest, showing stars to magnitude 11 and below).
Link to chart, RR Sco: http://charts.aavso.org/SCO/RR_SCO/RRSCO-B.GIF
Note that this is NOT a reversed chart as is used with the ETX and LX scopes in which the field has north at top and EAST at right; the reversed chart from the AAVSO is not available for this star.
With a total cycle of 279.7 days, this is an easy star to keep up with. Note from the light curve shown below that the star reaches a VERY SHORT peak at maximum and then fades rapidly but predictably to a very short, but somewhat longer minimum brightness, only to increase again.
Since the maximum can fluctuate between less than 6th magnitude to up to 5.2, it is important for observers with moderate telescopes to monitor this star about every week; merely compare the star's brightness to one of the many comparison stars (or extrapolate between two or more) and write down your estimate. Send that estimate about once a month to: http://www.aavso.org so that they can include YOUR observations in the scientific database about this variable star.
Object 10 - A MOST UNUSUAL OBJECT, I must say....Powerful X-Ray Emitter Scorpius X-1!
To say that this is a "must see" is most definitely an overstatement since you are likely to NOT see anything when you GO TO this object! But....nonetheless, are YOU going to go through life without saying that you have SEEN the "....MOST POWERFUL EMITTER OF X-RAYS IN THE UNIVERSE?" Even better, wouldn't you like to actually show this object to lots of people? Well, now you can.
What you won't see is a mysterious burst of X-rays coming from the northern realms of Scorpius; this object is the most powerful source of X-rays known and first discovered in 1962 in a space flight. For identification purposes, use the accompanying star chart that I have put together; although it does not reach the magnitude 13.1 which this mysterious source appears to be....it will at least get you close enough to say "...my eyes have seen it; I may not know it, but my eyes have actually seen this object." In the chart below, the wide field chart (large one) shows the northern part of Scorpius, with the stars Antares and Dschubba clearly marked; the small square is the area of X-1; note that the small white-on-black chart at upper right is REVERSED to correspond with the image as seen in a Maksutov or Schmidt Cassegrain. The faintest star shown in the small chart is about magnitude 13.0.
At a distance of about 1600 light years, Scorpii X-1's nature is still not clearly understood; it most certainly is a "double-something," as deduced from careful observations since 1962. It is possibly a high energy NEUTRON STAR being encircled by a cooler white dwarf star that has one side of it (pointing toward the neutron star) strongly heated and energized creating a hot disk or shell about the size of planet Earth.
Remember, this object is DIFFERENT: it is not the reward of "seeing something spectacular" with this one...it is the fact that you are looking at and showing to others what might be the most active source of X-radiation in the Universe! Sometimes the imagination has to supplement the realization. This is one of those times.
Object 11 - A Fantastic Globular Cluster - Messier 4
You owe it to yourself to do a very detailed comparison between Messier 4 - a VERY bright and spread-out globular just west of Antares - and Messier 80, another globular but extremely small and tightly compacted toward its center. The differences in these two are fantastic and worth looking at time and time again. You might guess by its size (14' arc, half the size of the moon!) that M-4 is relatively close to us compared to tiny (3.3' arc) Messier 80 which is five times more distant. Interestingly the two of them are about the same brightness, with M-4 being magnitude 6.7 and M-80 at 7.4....however, M-4 will appear to be the DIMMER of the two objects. This is because the total light ("integrated light") is spread out over the large total area; thus the more compacted object will appear much more concentrated in luminosity. Messier 4 is only 15. degrees due west of bright Antares, and sure enough the neat little ETX 60 and 70 scopes can get them BOTH in the same low power field of view, offering absolutely stunning views of this portion of the summer Milky Way. Messiers 4 and 80 are my personal two favorites among the globular clusters. (see my Guide to Observing Globular Clusters at: http://www.weasner.com/etx/ref_guides/globulars.html ). Messier 4 exhibits a wide spread of nearly equal magnitude 13 or slightly brighter; there are maybe 30 or 40 such stars which you might think, because of that brightness, would be tough to resolve in our scopes....they are not. Even with the ETX 90, many peripheral stars can clearly be seen at about 120x; the ETX 125 shows good star images all the way to the center and the views in the LX 90 are outstanding, with stars appearing as a "splat" of star dust filling a medium power eyepiece. Unlike many globular clusters, M-4 does NOT exhibit a very condensed core or central nucleus, but rather a nice even spacing of stars throughout its large expanse.
Objects 12 and 13 - A Fine and Close Pair of Galactic Clusters, Messiers 6 and 7
Ideal for the smallest of telescopes and presenting perhaps the finest of all shots of the Milky Way star clouds, Messiers 6 and 7 team up near the tail (five degrees north) of the Scorpion to provide an outstanding low power wide field vista. Both can be seen as "faint fuzzies" to the naked eye on a very clear and moonless night. Messier 6 is large, about the size of the moon's disk in the sky. In the ETX 60 and 70 (which are the ideal instruments for this cluster, by the way!), up to 60 stars to magnitude 10.5 can be clearly seen in this packed large cluster over a field of nearly one degree! Although the entire cluster can be seen in wide field eyepieces of the ETX 90 and larger scopes, there is no advantage to aperture here. With a wide field, observers can begin to imagine the shape of a winged "butterfly" for M-6....hence the nickname: "Butterfly Cluster" that appears on your name AutoStar library directory. Messier 6, at a distance of about 1300 light years is the more distant of the two galactic clusters.
Messier 7 is only 3.5 degrees southeast of Messier 6 and appears larger, has more stars and some associated nebulosity which CAN be seen on a dark night at the very low magnifications. Unlike a pretty "butterfly" of M-6, Messier 7 outlines pretty much a "square" shape in very low power instruments, showing about 25 stars brighter than magnitude 9.2! For observers with the LX 90 telescope, use that larger 8" aperture to look for a very faint GLOBULAR CLUSTER in the same field of view as M-7! NGC 6453, magnitude 11, is only 20' arc northwest of the brightest star of this group; it is very small and unresolvable, but will appear like a "fuzz ball" in the LX 90.
Object 14 - Messier 9 - A Fine Globular Cluster in Ophiuchus - Here for comparison purposes
Messier 9, in the constellation of Ophiuchus, is discussed in that "GO TO" GUIDE (see http://www.weasner.com/etx/ref_guides/ophiuchus.html ). Please use your GO TO function to slew over to this nice globular - it is a classic shape, size, and morphology - to use as a comparison for Messiers 4 (discussed above) and 80 (discussed below). You will see clearly just how different both M-4 and M-8 are from the "norm" of globulars. This is a great exercise and a really good "talking point" comparison for star parties and educational sessions with the telescope.
Object 15 - A Wonderful Globular Cluster - Messier 62
While comparing the "typical nature" of Messier 9 (above), be sure to include this globular in the judging as well. Messier 62 is also unique. Located about 7 degrees southeast of bright Antares, a small telescope will see the cluster as a very nice bright glow in which a very pronounced central "core" of brightness is contained. This is very evident in the ETX 90, although typically NO stars can be resolved clearly with this telescope. The ETX 125 begins to hint at some stars around the periphery, but the LX 90 will only break down a very few more. It is a tough object. Its total magnitude is 8.3, but that brightness is packed so tightly in the center that little can be resolved. Remember that the AVERAGE brightness of its 30 brightest stars is only magnitude 16! It can be seen clearly is the ETX 60 and 70 and is well worth searching out. Expect it to look like a very faintly illuminated tennis ball far out into the sky in all scopes.
Object 16 - The Fine Globular Cluster Messier 80
Discussed above, this is a really nice and compact little globular, well worth spending some time on comparing to Messier 4 (above). M-80 appears very much like M62, only about 1/3 smaller; curiously, the stars around the fringes of M-80 are more readily seen than those of the larger cluster. The ETX 90 is about the smallest scope that will see peripheral stars (on very dark nights and medium-high power) in this cluster. You MUST observe the area from this globular WESTWARD with very low power and wide field in slow scans....it is here that we observe William Herschel's "hole in the heavens", a pronounced dark area of the Milky Way where the background stars are obscured by the dark dust of the Milky Way. On a very dark night in remote areas, you will plainly see these areas "where stars ain't...." as it was put to me once.
Object 17 - The "Bug Nebula" - NGC 6302
As in tiny bug. This little diffuse nebula measures only 2' arc long by 1' arc wide, about three times the size of Jupiter in the same medium power eyepiece. It is too small and faint (magnitude 10.0) for the ETX 60 and 70 but begins to show somewhat in the ETX 90 as a "bug-like" shape. Look for a faint glowing outline amidst a very bright star field; it will stand out against the stars clearly; some magnification (about 30x per inch) is required to really get a good look at it. It is on the named objects of your Deep Sky AutoStar library list. Let us know your impressions of this odd object....collect it, or squash it?
Objects 18 and 19 - Gorgeous Galactic Clusters - NGC 6231 and NGC 6242
These two glittering gems are like pendants hanging from fine necklaces of space. They are absolutely breathtaking on a very dark night, but unfortunately located in very far southern skies for high northern latitudes. Both clusters are excellent objects for all size telescopes, but wide fields and low powers are preferred. NGC 6231 contains about 25 stars to magnitude 9, scattered over an area about half the size of he moon; thus about 15x per inch aperture of your telescope is ideal. Larger telescopes can detect more; the ETX 125 should reveal about 90 stars total, with some 120 or so visible in the 8" aperture. Not so many are visible in the much fainter and more distant NGC 6242, but it is still a nice object. More compact and with fainter stars, only about 20 total stars can be seen with the ETX 125 or larger scopes. About half that many can be discerned in the ETX 90. Expect NGC 6242 to be about half the size of NGC 6231. In very wide field eyepieces, take the time to scan between these two clusters; you are looking at an absolutely incredibly star-rich area of our Milky Way's Sagittarius Arm. You could spend an entire night looking through this region with new objects coming into the field with every turn.
Object 20 - NGC 6388 - Small but nice globular cluster
This is an overlooked pretty, yet small, globular cluster, VERY far south in Scorpius. At magnitude 7.1, if the object was higher in the northern sky it would be certainly one of the Messier objects. It is actually a bit larger than M-80, at almost the same distance in space and only a slight bit dimmer. As with M-80, the ETX 125 will show some outer sprinkles of stars; the LX 90 offers little gain even with the larger aperture. With the ETX 60, 70 and 90, expect a nice compact and bright fuzz ball due south of the Scorpion's "stingers"
WANDERING ABOUT....YOUR NEW "USER OBJECT" IN SCORPIUS
How can we resist.....you already KNOW what the recommended new "User Object" will be, don't you? Even if you can't SEE it...it still needs to be in your AutoStar for your next neighborhood star party or big astro-bash in the mountains. Show people something they cannot see, only feel (and even still not know that either!). That's right, for our Scorpius User Object, let's key in the coordinates of Scorpius X-1, the most powerful X-Ray emitter in the Universe (so far as we know). Get the coordinates for OBJECT 10 (above) And LET'S LOAD THIS CONVERSATION PIECE INTO OUR USER OBJECTS! Take your Autostar and key in the particulars for "x-1 Scorpii." This will your FIRST radiation source to your AutoStar library of interesting and unusual "User Objects."
On AutoStar, go to: "Select/Object [enter]...." scroll down to "User Object" [ enter]. Now enter the coordinates given above for "X-1 Scorpii", using the number keys on AutoStar. After entering and pressing "Enter" yet again, scroll down one and you can list the magnitudes of both stars [Enter]. One scroll more after that and you may type in your brief description of the object....(I like: "Warning: Radiation!") [Enter again].
Next Constellation GO TO" TOUR Installment: CYGNUS, among my favorites of constellations although it is not full of "show material" like Scorpius. In this wonderful Northern Cross we will explore the large planetary nebula, the Dumbbell Nebula, the wonderfully exciting colored double star Alberio, the North American Nebula, and much, much more.....
Good Observing and explorations of this wonderful world of deep space!
P. Clay Sherrod
Arkansas Sky Observatory
Conway / Petit Jean Mountain
Return to the top of this page.
Go back to the Observational Guides & References page.
Go back to my ETX Home Page.