CONSTELLATION GUIDE Last updated: 22 April 2001

"GO TO"....LEO
Entering the Domain of the "Celestial Lion" With Your ETX and LX 90 Telescope

From: sherrodc@ipa.net (Clay Sherrod)

ABOUT THE CONSTELLATION "GO-TO" GUIDES!

This is the second installment, "GO TO LEO", of our constellation study guides for ETX and LX 90 telescope users. Last installment featured Ursa Major, located high in northern declinations for easy year-round viewing. This Guide will feature a constellation equally as recognizable yet one located very close to the CELESTIAL EQUATOR, or roughly centered on either side of "0 degrees" declination. As will all of our "GO TO GUIDES", it features a "start" with an easy GO TO to the bright star REGULUS, and then proceeds through the many fine examples of double and multiple stars, galaxies and interesting objects within reach of YOUR telescope! From distant galaxy groups to beautifully-colored and complex multiple star systems with discussions along the way tell you what to expect from each telescope size and type. All objects will be discussed with exact descriptions of what the viewers of the ETX 60/70, ETX 90, ETX 125, and LX 90 should expect to see...and what to NOT expect to see!

The finest stellar and deep sky objects in the constellation will be featured....and - yes - there will be something for everyone and every telescope...Even naked eye and binoculars when appropriate!

Discussed are useful magnifications for EACH GO TO object, what type of night and conditions are needed to see certain details, double stars that can be resolved in each telescope model, and much, much more. It is your complete GUIDE for your deep sky observing pleasure and a very handy tool for use at your next star party!

Needless to say, it WILL put your AutoStar to work for you in a most efficient and enjoyable way!

I hope you will enjoy these comprehensive GUIDES to "Touring the Constellations" which will feature a NEW constellation about every two weeks, complete with diagrams, charts and illustrations. Please let us hear from you with summations of YOUR observations through these constellation tours!

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Introduction -
Few constellations really appear to us as what their mythological designations signify. I have never seen a "virgin" Virgo, an "archer" in Sagittarius, or a goat herder in Auriga. But some among those 88 constellations which remain today are unmistakable in their identify. Perhaps this is why - even before communications and travel between the continents, and before cultural mythology and lore were exchanged between peoples of the world - that some constellations have always had a common association world-wide; such is the case with Scorpius, the Scorpion....Orion, a hunter or a great persona of a man....Ursa Major as a large bear.

And among those must be LEO, the celestial "lion" that roars its way into our skies each spring.

No matter how you draw the lines, this figure still comes out looking like a lion. Curiously, when upside-down, as it would be viewed by our observers south of the equator, it is very difficult to even recognize, much less associate a lion, this constellation.

Although the ancient Egyptian skywatchers worshipped this constellation as "The House of the Sun" to signify when the sun entered the star group, associated with the flooding of the Nile River, (thereby providing precious water for irrigation to the parched arid surroundings) they too perhaps signified this constellation as "lion-like" in both hieroglyphic renderings as well as a possible association to the great Sphinx of the Egyptian plains.

After the birth of Christianity, the constellation was known to early Christians as Daniel's Lion's Den, from the Book of Daniel. Earlier, the book of Genesis signifies this constellation as the symbol for Judah.

In ancient China, starwatchers were a bit different in their views of this group....to them, it was the "Great Yellow Serpent" or "dragon."

Note the many bright stars in the drawing (Figure 1) above that outline the head, body, tail and even feet of the great celestial lion. The stars of the lion's "mane" are also known as the "SICKLE" from its characteristic shape, and it is among those "sickle stars" that the famous and beautiful "headlight double" - Gamma Leonis is found.

As we explore Leo, we are entering the "Realm of the Galaxies" from our vantage point in space. Just east of Leo is the fantastic galaxy-packed constellation of Coma Berenices and others which exhibit hundreds of thousands of galaxies to the world's largest telescope. There are perhaps over 10,000 galaxies photographable to the world's largest telescopes in Leo alone.

The bright star REGULUS is so near the celestial equator (only 12 degrees north) that it provides an excellent bright white target for both star tests and for accurate polar alignment using the "drift method."

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YOUR LEO "GO TO" TOUR - THE CONCISE DIRECTORY

We will concentrate on 11 objects in LEO for this quick tour; all are in reach of every telescope in our "ETX and LX family" yet each telescope will demonstrate uniquely different and challenging aspects of the objects. In addition to the 11 finest objects, there are MANY more exciting things to see in our celestial Lion than those given here - hundreds of double and multiple stars, hundreds of galaxies and deep sky objects, stars of curious colors and motion - that can be found with your telescope. Perhaps more than any other constellation of Spring, Leo offers a wealth of fine double stars to test the limits of your telescope!

I recommend good a good star atlas and/or chart which lists the finest objects constellation-by-constellation; you merely need to hold down your MODE key on the AutoStar for three (3) seconds and the RA and DEC coordinates appear for the telescope. Merely press "GO TO" and the cursor appears prompting you to enter the Right Ascension of the object if it is NOT listed among the objects in the AutoStar library; once the RA is entered, press "Enter" and the cursor once again prompts for the Declination coordinates (these coordinates for epoch 2000) are found in all good observing guides). Once those are entered, merely press "GO TO" once again and your ETX or LX 90 will slew to the position of the object!

The following constellation guide to objects at the end of this TOUR will describe all the details of each object you wish to view and give specifics as to visibility in YOUR telescope model.

Click for full size version.

The special star chart here will get you started, as it demonstrates the relative positions of all objects in this "tour" to the conspicuous stars outlining the distinct figure of our celestial lion."

Following is the complete 11-object list for your "GO TO TOUR" of Leo; you may wish to find the majority of the objects from the AutoStar library (for example, you can merely pull up Messiers 65 and 66 by going to "Object/Deep Sky/Messier Object/M-81....enter....GO TO" or...if you want to experiment and be a "better AutoStar user", try entering the following coordinates as described under MODE above.

OBJECT 1:
    star - REGULUS (alpha Leo) - R.A. 10H 06' / DEC + 12 13 -  Magnitude:  1.4
OBJECT 2:
    optical double star - DENEBOLA (beta Leo) - R.A. 11H 47' / DEC + 14 51 - Magnitude: 2.1
OBJECT 3:
    beautiful double star - ALGEIBA (gamma Leo) - R.A. 10h 17' / DEC + 20 06 - Magnitude: 1.9
OBJECT 4:
    multiple star + galaxy - TANIA AUSTRALIS (MU UMa) + ngc3184 - R.A. 10h 19' / DEC + 41 45 
    Magnitude: 3.1 (galaxy is 10.3m)
OBJECT 5:
    close nice double star - Leo 7704 - R.A. 10h 14 / + 17 59 - Magnitudes: 7.2 & 7.4
OBJECT 6:
    famous variable star - R LEONIS - R.A. 09H 45' / DEC + 11 40 - Magnitudes:  4.4 TO 11.3 (45 DAYS)
OBJECT 7:
    great double for ETX 60/70 - ALULA AUSTRALIS - R.A. 11H 16' / DEC +31 49 - Magnitudes: 4.4 & 4.8
OBJECT 8:
    double star - Leo 90 (good test for ETX 90) - R.A. 11h 32' / DEC +  17 04 - Magnitudes:  6.0 & 7.1
OBJECT 9:
    galaxy cluster - Messiers 65 (ngc 3623), 66 (ngc3627) and ngc3628 -  R.A. 11h 16' / DEC + 13 23 
OBJECT 10:
    galaxy cluster - Messiers 95 (ngc 3351), 96 (ngc3368) & 105 (ngc3379) - R.A. 10h 41' / DEC + 11 58
OBJECT 11:
    galaxy - ngc2903 - R.A. 09h 29' / DEC + 21 44 - Magnitude: 9.1

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A VISUAL GUIDE TO OUR OBJECTS IN LEO -

Object 1 - Bright Star Regulus (Alpha Leonis)
This bright white star is known throughout the world as "The Heart of the Lion," and fittingly so. It is a "B" type very bright star, shining at about 160 times the light of our own sun. Even though it is white, it is a very "late" star, having depleted much of its hydrogen-rich fuel and now exhibiting fusion through helium.

In ancient middle eastern cultures, Regulus was one of the four (4) "royal" stars: Regulus, Aldebaran, Fomalhaut and Antares. The Babylonians before them depicted Regulus as "the King", with no mention as to a reference to a lion, only to royal association. Because of the seasonal rains that bring life-giving nutrients to the arid regions, many such cultures associated this star - as did the Egyptians the entire constellation (see above) - to great floods and a time of increased agriculture.

An interesting aspect of Regulus is its location so close to the ecliptic (see the constellation chart above); what this means to amateur astronomers is that many times this bright star is OCCULTED, or "covered up" by the moon as the earth's satellite slowly moves eastward through the ecliptic. Such occultations are spectacular when involving a bright star. In 1959 Regulus was actually occulted by the planet VENUS, an event so rare that many centuries will pass before anything close occurs again.

Look for a very difficult (because of the brightness of Regulus) companion star at a Northwest angle from Regulus at a distance of 180" arc, or about 5 Jupiter widths away; medium-to-high power is recommended to see its companion. This 8th magnitude star is, itself, double, but it requires at least a 16-inch telescope to resolve.

Object 2 - Bright Optical Double Star DENEBOLA (beta Leonis)
This bright yellow star, only 43 light years distant, signifies the "Lion's Tail" of Leo; also Arabic is the name "Serpha" which translates "keeper of the weather," perhaps also a reference to the flooding of the Nile river when the sun moves into the boundaries of Leo.

There is a significant difference between an "optical double" and a "physical double" star; the optical double, like this target star, Denebola, only APPEARS to be two related stars when, in fact, they are seen at two greatly different distances. In fact, Denebola has MANY optical companions; the one visible in the ETX 90 and larger telescopes is nearly due south, about 4' arc, from the bright yellow main star.

Object 3 - Bright Star Double Star ALGEIBA (gamma Leonis) "The Auto Headlight Stars"
This star, folks, is a keeper. If you look at NOTHING ELSE in Leo, you MUST see this incredible sight. Not only is this one of the finest - and easiest resolvable - double stars in the sky, but it shows a remarkable brilliant deep yellow coloration with both components, and they appear as to automobile HEADLIGHTS coming right at you out of the sky.

This is an excellent test star for the ETX 60/70 but easily resolvable at medium magnifications in larger scopes. In my ETX 125 and LX 90, I frequently have my best views of this double at about 400x (the 4.7mm UWA Plossl). The figure below shows the incredible and unforgettable sight of this star seen at very high power.

When highest in the sky, steady air and high magnification shows Algeiba with two distinct yellow Airy disks surrounded by two very nice rings of light if your system is perfectly collimated. There is about a magnitude difference (2.1 and 3.4) between the two of them.

The name "Al Jabbah" appropriately signifies the "Lion's Mane" from the original Arabic designation.

After you have "looked it all up", turn your telescope for a moment away to the northwest from Algeiba about 2 full degrees and put in your lowest power eyepiece (the ETX 60 and 70 will have a great benefit here). The incredible LEONID meteor show (peaks November every year) actually appears to emanate from this exact location as the Earth turns into the swarm of debris left from Comet Swift-Tuttle in 1866!

Object 4 - Double Star 7704 Leonis
This will be a good test for you to enter your own R.A. and DEC coordinates on the AutoStar since it is not part of the AutoStar library of double stars or named stars. Enter the coordinates (listed above) as described earlier via the MODE key and once entered, merely push "enter" and the telescope will slew to this very, very nice star! This is a TEST for your ETX 125....even though both stars are 7.5 magnitude, they are only 1.2" arc apart, theoretically resolvable. I have actually been able to see some "elongation" in the ETX 90 RA of these two stars, but no clean separation; however, both the ETX 125 and LX 90 will definitely split it. High magnification is a MUST. Note: make sure you have the right star....there are several of that similar magnitude nearby!

Object 5 - Great double star "54 Leonis" - A super double star test for the ETX 60 and 70
Again, use the "mode" key on this one and enter your coordinates. This star is not so difficult to find, however, as both are brighter - magnitudes 4.5 and 6.3! They are separated by over 6" arc so the ETX 60/70 with high power can plainly show this very pretty pair. Use low powers on the ETX 125 and LX 90....medium magnification (120x) on the ETX 90 is ideal.

Object 6 - Variable Star R LEONIS
This is our very first variable star on the Constellation Tour Guides, and it is one of the most famous and easy-to-monitor for all of our scopes. The entire cycle of brightening (to magnitude 4.4, naked eye!) and dimming (to 11.3, right at the ETX 70 threshold on a dark night) can be followed in a very short period of only 44.9 days! You can keep a log and monitor this red "Mira-type" star as it goes through its pulsating increase in size to maximum and slow (yes, actually shrinking) to minimum. Once your data is collected for several cycles, you can compile a "light curve" exactly like the one shown below!

R Leonis is known as a "long period variable" and perhaps one of the best for getting started in variable star observing (see my Guide to Variable Stars.... here on this web site under "Observational Guides...."). Below is a click-on for you to obtain the wide-field chart for R Leonis from the American Association of Variable Star Observers; this chart is suitable for observing magnitudes when the star is brightest....access www.aavso.org for a full set of downloadable charts to watch this wonderful star through its dimmest part of the cycle.

Reversed (ETX/LX orientation) R Leonis Finder/Comparison Chart link:

    http://charts.aavso.org/LEO/R_LEO/RLEO-B.GIF

Object 7 - Double Star for ETX 60/ 70 Test - Beautiful object for all!
This star, ALULA AUSTRALIS, is actually in the constellation of Ursa Major (one of its back paws) and was featured in the previous constellation TOUR; if you missed it, check it out while you are here. This is a fine double star that is challenging for the ETX 60 and 70 at medium power and a beautiful sight in all telescopes.

Object 8 - Nice Double Star 90 Leonis - key in your coordinates to find this one!
This double star is an excellent test object for the ETX 90, with the two stars (magnitudes 6.1 and 7.1) separated by about 3" arc, which should be easily resolvable on a steady night with high (about 160x+) magnification. The ETX 125 will easily split these two components at 73x, as will the LX 90 at 77x. The two stars will appear very close together, nearly equal in brightness, with the dimmer of the two a bit West of due SOUTH from the brighter star. If you cannot immediately resolve, check to make sure you have the correct star located via the "Mode" key to enter your own R.A. and DEC. Also, increase your magnification if the star does not readily split into its two components.

Object 9 - Galaxy Group - Messiers 65, 66 and ngc 3628
This is one of the nicest and easiest-to-locate of your GO TO objects; both M-65 and M-66 will be in the same lowest power field of view (use your 26mm or similar low power eyepiece); with the many other stars in the field, it is a remarkable sight, with M-65 appearing distinctly oval in shape and brighter than M-66 to its "left" in the field of view. Both galaxies are oval in shape as seen in your scopes, with M-65 seemingly more cigar-shaped but with M-66 showing a bit more detail on its southern perimeter to the larger ETX 125 and LX 90 on VERY dark nights. This detail is actually extensions of a prominent galaxy "arm" and associated star clusters within that arm. M-65 is a uniform, featureless glow in all scope sizes. Just to the north of these two, and still within the same fields of the ETX 60, 70 and 90, is the wonderful ngc3628 galaxy, seen nearly edge-on with a very pronounced dark "lane" across its edge. This dark "streak" can be seen clearly with the ETX 90 on a very, very dark night, but NOT with the ETX 60 and 70; the galaxy, however, CAN be seen with these scopes. The ETX 125 and LX 90 reveal a great amount of detail on ngc3628 under perfect dark sky conditions with magnifications from 150x to 210x. You might be able to distinguish the dark lane as it "separates" one half of the galactic hub (it will appear brighter north of the dark lane and slightly more narrow and dimmer below, or south, of the dark lane). These are but a few of the remarkable collection of galaxies throughout this region of sky.....use some good reference books and the next clear moonless night to peer deeper into space that you likely have ever gone!

Object 10 - Galaxy Group - Messiers 95, 96 and 105
Like the group just described, this is yet another close assemblage of fairly bright galaxies; all should be visible in the same field of view with the ETX 90; the ETX 125 and LX 90 will likely require (unless the 40mm super plossl or equivalent is used) you to move a bit to the northeast from M-96/95 to access M-105. The three galaxies are about 8' arc apart, making a pretty equal triangle. M-96 is actually a full magnitude brighter than M-95 (magnitude 10.1), although it is somewhat smaller. Messier 105 (magnitude 9.5) is also brighter than M-95, but can easily be mistaken for a "fuzzy star" as it is very small (only 2' arc across) and very round. It is very difficult to distinguish in the ETX 60 and 70 and requires medium power in the larger telescopes.

Object 11 - Galaxy ngc2903
This bright (magnitude 9.3) oval-shaped galaxy will look quite symmetrical in the ETX 90 and larger scopes, appearing elongated almost due north-south; it is very bright toward the center and then falls off rapidly toward its large 11' arc length. Because it is so large, its brightness is scattered over a very large area and thus appears dimmer than it actually is. The larger aperture ETX 125 and LX 90 will clearly show some "rough" mottling across this face-on galaxy, with many dark and light zones appearing where star clouds and dark matter actually exist in this nice galaxy.

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WANDERING ABOUT....YOUR NEW "USER OBJECT" FOR LEO

This brief GO TO Tour of Leo has revealed its most interesting secrets. But please do not stop here. Go ahead and locate many of the hundreds of other ngc galaxies that are present in this constellation.....there are several more interesting double and multiple stars that are within the reach of your telescope. In addition, use this opportunity to actually LOAD ANOTHER USER OBJECT onto your AutoStar!

Your friends, family and fellow stargazers would be delighted if you could show them the "Automobile Headlights in Leo" in your ETX or LX 90; merely go into "Select/Object/User Object....[enter]" and then add in the coordinates (R.A. and DEC given above) and a name/description of the beautiful yellow "headlights" of gamma Leonis and press "enter" to store your information into the AutoStar library!

Next Constellation "GO TO TOUR" Installment: BOOTES and some remarkable globular clusters and other objects!

Good observing and explorations of the wonderful world of deep space!

P. Clay Sherrod
Arkansas Sky Observatory
Conway / Petit Jean Mountain
Arkansas

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