Stalking the Lunar X

This week offers observers a shot at capturing a fascinating but elusive lunar feature.

But why study the Moon? It’s a question we occasionally receive as a backyard astronomer. There’s a sort of “been there, done that” mentality associated with our nearest natural neighbor in space. Keeping one face perpetually turned Earthward, the Moon goes through its 29.5 synodic period of phases looking roughly the same from one lunation to the next. Then there’s the issue of light pollution. Many deep sky imagers “pack it in” during the weeks surrounding the Full Moon, carefully stacking and processing images of wispy nebulae and dreaming of darker times ahead…

But fans of the Moon know better. Just think of life without the Moon. No eclipses. No nearby object in space to give greats such as Sir Isaac Newton insight into celestial mechanics 101. In fact, there’s a fair amount of evidence to suggest that life arose here in part because of our large Moon. The Moon stabilizes our rotational axis and produces a large tidal force on our planet. And as all students of lunar astronomy know, not all lunations are exactly equal.

A daytime capture of the Lunar X. (Photo by Author).
A daytime capture of the Lunar X. (Photo by Author).

This week, we get a unique look at a feature embedded in the lunar highlands which demonstrates this fact. The Lunar X, also sometimes known as the Purbach cross or the Werner X reaches a decent apparition on March 19th at 11:40UT/7:40EDT favoring East Asia and Australia. This feature is actually the overlapping convergence of the rims of Blanchinus, La Caille and Purbach craters. The X-shaped feature reaches a favorable illumination about six hours before 1st Quarter phase and six hours after Last Quarter phase. It is pure magic watching the X catch the first rays of sunlight while the floor of the craters are still immersed in darkness. For about the span of an hour, the silver-white X will appear to float just beyond the lunar terminator.

Visibility of the Lunar X for the Remainder of 2013.

Lunation Date Time Phase Favors
1116 March 19th 11:40UT/7:40EDT Waxing East Asia/Australia
1116 April 3rd 3:20UT/23:20EDT* Waning Africa/Europe
1117 April 17th 23:47UT/19:47EDT Waxing Eastern North America
1117 May 2nd 16:19UT/12:19EDT Waning Central Pacific
1118 May 17th 10:51UT/6:51EDT Waxing East Asia/Australia
1118 June 1st 4:31UT/0:31EDT Waning Western Africa
1119 June 15th 21:21UT/17:21EDT Waxing South America
1119 June 30th 16:04UT/12:04EDT Waning Western Pacific
1120 July 15th 7:49UT/3:49EDT Waxing Australia
1120 July 30th 3:16UT/23:16EDT* Waning Africa/Western Europe
1121 August 13th 18:50UT/14:50EDT Waxing South Atlantic
1121 August 28th 14:27UT/10:27EDT Waning Central Pacific
1122 September 12th 9:50UT/5:50EDT Waxing East Asia/Australia
1122 September 27th 2:00UT/22:00EDT* Waning Middle East/East Africa
1123 October 11th 19:52UT/15:52EDT Waxing Atlantic Ocean
1123 October 26th 14:12UT/10:12EDT Waning Central Pacific
1124 November 10th 10:03UT/5:03EST Waxing East Asia/Australia
1124 November 25th 3:14UT/22:14EST* Waning Africa/Europe
1125 December 10th 00:57UT/19:57EST Waxing Western North America
1126 December 24th 17:07UT/12:07EST Waning Western Pacific
*Times marked in bold denote visibility in EDT/EST the evening prior.

 

Fun Factoid: All lunar apogees and perigees are not created equal either. The Moon also reaches another notable point tonight at 11:13PM EDT/ 3:13 UT as it arrives at its closest apogee (think “nearest far point”) in its elliptical orbit for 2013 at 404,261 kilometres distant. Lunar apogee varies from 404,000 to 406,700 kilometres, and the angular diameter of the Moon appears 29.3’ near apogee versus 34.1’ near perigee. The farthest and visually smallest Full Moon of 2013 occurs on December 17th.

The first sighting of the Lunar X feature remains a mystery, although modern descriptions of the curious feature date back to an observation made by Bill Busler in June 1974. As the Sun rises across the lunar highlands the feature loses contrast. By the time the Moon reaches Full, evidence of the Lunar X vanishes all together. With such a narrow window to catch the feature, many longitudes tend to miss out during successive lunations. Note that it is possible to catch the 1st and Last Quarter Moon in the daytime.

A 1st Quarter Moon with the Lunar X (inset). (Photo by Author).
A 1st Quarter Moon with the Lunar X (inset). (Photo by Author).

Compounding the dilemma is the fact that the lighting angle for each lunation isn’t precisely the same. This is primarily because of two rocking motions of the Moon known as libration and nutation. Due to these effects, we actually see 59% of the lunar surface. We had to wait for the advent of the Space Age and the flight of the Soviet spacecraft Luna 3 in 1959 to pass the Moon and look back and image its far side for the first time.

We actually managed to grab the Lunar X during a recent Virtual Star Party this past February. Note that another fine example of lunar pareidolia lies along the terminator roughly at the same time as the Lunar X approaches favorable illumination. The Lunar V sits near the center of the lunar disk near 1st and Last Quarter as well and is visible right around the same time. Formed by the confluence of two distinct ridges situated between the Mare Vaporum and Sinus Medii, it is possible to image both the Lunar X and the Lunar V simultaneously!

A simultaneous capture of the Lunar X & the Lunar V features. (Photo by Author).
A simultaneous capture of the Lunar X & the Lunar V features. (Photo by Author).

This also brings up the interesting possibility of more “Lunar letters” awaiting discovery by keen-eyed amateur observers… could a visual “Lunar alphabet be constructed similar to the one built by Galaxy Zoo using galactic structures? Obviously, the Moon has no shortage of “O’s,” but perhaps “R” and “Q” would be a bit more problematic. Let us know what you see!

-Thanks to Ed Kotapish for providing us with the calculations for the visibility of the Lunar X for 2013.

 

Weekly SkyWatcher’s Forecast: October 15-21, 2012

Greetings, fellow SkyWatchers! Whoops! (she blushes) I got so lost this weekend in researching Comet ISON that I almost forgot to post the forecast! Ah, well… As they say, better late than never, eh? If you do nothing else this week, be sure to catch the close apparition of Mercury and the “Earthshine Moon” on Wednesday and stay up late Saturday night to watch the Orionid Meteor Shower! In case I forget, just meet me in the back yard…

Monday, October 15 –Today in 1963 marks the first detection of an interstellar molecule. This discovery was made by Sander Weinreb (with Barrett, Meeks, and Henry) on the MIT Millstone Hill 84-foot dish. The discovery was made possible by new correlation receiver technology, and picked up a hydroxyl molecule in an absorption band. By using the radio galaxy Cas A as a background continuum source, the detection occurred at 1667.46 MHz and again at 1665.34 MHz. By the dawn of 2000, nearly 200 different interstellar molecules had been identified and many of these are classified as organic.

Tonight is New Moon! Let’s see what’s up there in the region of Cas A using visible light. The nearest bright star to Cas A is Beta Cassiopeiae – the bright star westward of the “W.” To locate the region of Cas A, go about three finger-widths due west of Beta and follow the subtle curve of three 5th magnitude stars. Cas A lies less than one degree south-southwest of the second star in the sequence of three. This star is a complex 5th magnitude multiple star system associated with variable star AR Cas.

Through binoculars, two stars of the AR system are easily resolved – the 4.9 magnitude primary is seen to be led across the sky by a 7.1 magnitude secondary (component C) which is a very tight double itself. Its 8.9 magnitude partner is resolvable in mid-sized scopes. Large aperture scopes may also be able to distinguish a 9.3 magnitude, second (B) component from the primary. Smaller scopes are back in the running again when attempting three 11th magnitude stars – none of which are close to the primary. Intermediate scopes can also hope to pick out a 12.9 magnitude H component northwest of C. 8.9 magnitude F also has a 9.1 magnitude near twin to the east-northeast. If you can see them all you should probably wrap an observatory building around your telescope – if one isn’t there already!

If you like to follow brightness changes in variables – AR Cas is not a good choice. This eclipsing type variable only fluctuates by a tenth of a magnitude over a period of 6 earth days.

Tuesday, October 16 – Let’s begin our evening by having a look at a radio source as we visit a pulsar located almost mid-way between Theta and Beta Capricorni – PSR2045+16.

While pulsars aren’t truly visible objects, there is still something undeniably cool about locating the field in which a rotating neutron star is sending out staccato pulses of radio waves anywhere between .001 and 4 seconds apart. If you have bright star 19 in the binocular field, then you know you’re in the right area for many radio sources, including many nearby quasars… Just imagine the possibilities!

Now let’s drop south-southeast of Beta Capricorni to have a look at a pair of doubles – Rho and Pi.

Northernmost Pi is a multiple system slightly less than 100 light-years away, with each discernable member also being a spectroscopic double. Separated by about an eighth of a light-year, look for a 5th magnitude yellow/white giant with a very close 9th magnitude companion. Further south is Pi, a triple star system which has a traditional name – Okul. Located around 670 light-years away, look for a bright blue/white 5th magnitude primary that is also a spectroscopic double – and its much easier C component, which is around magnitude 8.

Wednesday, October 17 – For naked-eye observers, enjoy the beautiful “Earthshine” Moon and the close apparition of Mercury!

While you’re out, be sure to gaze upon one of the finest of stars, Vega. Facing West at just after sundown, Vega is bright enough to shine even in the city and will appear just slightly below the zenith. The name Vega means “Falling Eagle” and it is the fifth brightest star in the sky. Enjoyed in either telescopes or binoculars, Vega has a wonderful bluish appearance and a lovely halo of spectra. This magnificent star holds a place in ancient legend and blossomed in our imaginations even more recently as it became the “star” of the movie “Contact”. As the western-most point of the “Southern Triangle”, Vega holds a special appeal for those born in the year 1985. Why? Because Vega is 27 light years away, the light you see from it tonight left the year you were born!

Now point those binoculars towards the northwestern corner of Capricornus and have a look a spectacular Alpha!

Although the Alpha 1 and 2 pairing is strictly a visual binary, that won’t stop you from enjoying their slightly yellow and orange colors. Collectively they are named Al Giedi, and the brighter of the pair is Alpha 2 at about 100 light-years distant; while Alpha 1 is around five times further away. Now power up with a telescope and you’ll find that both stars are also visual doubles! While the companion stars to both are around the same magnitude, you’ll find that Alpha 2 is separated by three times as much distance. Be sure to mark your observation lists and enjoy!

Thursday, October 18 – Today in 1959, Soviet Luna 3 began returning the first photographs of the Moon’s far side. Also today – but in 1967 – the Soviets again made history as Venera 4 became the first spacecraft to probe Venus’ atmosphere.

Have you checked out Mars lately? Mars is now leaving the constellation Scorpius and entering Ophiuchus. At more than 2 AU away from Earth, Mars has become quite dim, and its minimal apparent visual brightness is +1.24 magnitude. Can you still spot a few of its more prominent features?

For a true telescope challenge, we’ll have to go out on a limb – the southeastern lunar limb – to have a look at an unusual crater. Named for the French agrochemist and botanist Jean-Baptiste Boussingault, this elliptical-appearing crater actually spans a handsome 71 kilometers. What makes Boussingault so unusual is that it is home to its own large interior crater – A. This double-ring formation gives it a unique stepped, concentric look that’s worth your time!

When we’re done? Let’s go have a look at Gamma Aquilae just for the heck of it. Just northwest of bright Altair, Gamma has the very cool name of Tarazed and is believed to be over 300 light-years away. This K3 type giant will show just a slightly yellow coloration – but what really makes this one special is the low power field!

Friday, October 19 – Our lunar mission for tonight is a revisit on a crater named for historian and theologian Denis Pétau – Petavius! Located almost centrally along the terminator in the southeast quadrant, a lot will depend tonight on your viewing time and the age the Moon itself. Perhaps when you look, you’ll see 177 kilometer diameter Petavius cut in half by the terminator. If so, this is a great time to take a high magnification look at the small range of mountain peaks contained in its center, as well as a deep rima which runs for 80 kilometers across its otherwise fairly smooth surface. To the east lies a long furrow in the landscape. This deep runnel is Palitzsch and its Valles. While the primary crater which forms this deep gash is only 41 kilometers wide, the valley itself stretches for 110 kilometers. Look for crater Haas on Petavius’ southern edge with Snellius to the southwest and Wrottesley along its northwest wall.

Now, let’s go have a look at the northeastern corner of Capricornus as we learn about Delta…

Its proper name is Deneb Algedi and this nearly 3rd magnitude star is a stunning blue/ white. Curiously enough, it’s a rather close star – only about 50 light-years from Earth. Hovering so close to it that we cannot even correctly assess its spectral type is a binary companion whose eclipsing orbit causes Delta to be a very slight variable – with a period of just about one day. In its own way, Delta is rather historic… For it was only 4 degrees north of this star that Uranus was first sighted by Galle in 1846!

Saturday, October 20 – Tonight, let’s check out a lunar map and go hunting! First let’s start with a look at the Mare Fecunditatus region: (1)Taruntius, (2) Secchi, (3) Messier and Messier A, (4) Lubbock, (5) Guttenberg, (6) Montes Pyrenees, (7) Goclenius, (8) Magelhaens, (9) Columbo, (10) Webb, (11) Langrenus, (12) Lohse, (13) Lame, (14) Vendelinus, (15) the Luna 16 landing site

Mare Fecunditatus Region Photographic Map – Image Credit – Greg Konkel

And here is a closer look at the area around Atlas and Hercules: (1) Mare Humboldtianum, (2) Endymion, (3) Atlas, (4) Hercules, (5) Chevalier, (6) Shuckburgh, (7) Hooke, (8) Cepheus, (9) Franklin, (10) Berzelius, (11) Maury, (12) Lacus Somniorum, (13) Daniel, (14) Grove, (15) Williams, (16) Mason, (17) Plana, (18) Burg, (19) Lacus Mortis, (20) Baily, (21) Atlas E, (22) Keldysh, (23) Mare Frigoris, (24) Democritus, (25) Gartner, (26) Schwabe, (27) Thales, (28) Strabo, (29) de la Rue, (30) Hayn.


Atlas and Hercules Region Photographic Map – Image Credit – Greg Konkel

Have fun marking off lunar challenge craters from your list!

After having looked at the Moon, take the time out to view a bright southern star – Fomalhaut (RA 22 57 39 Dec -29 37 20). Also known as “The Lonely One,” Alpha Piscis Austrini seems to sit in a rather empty area in the southern skies, some 23 light-years away. At magnitude 1, this main sequence A3 giant is the southernmost visible star of its type for northern hemisphere viewers, and is the 18th brightest star in the sky. The Lonely One is about twice the diameter of our own Sun, but 14 times more luminous! Just a little visual aid is all that it takes to reveal its optical companion…

Now we are slipping into the stream of Comet Halley and into one of the finest meteor showers of the year. If skies are clear tonight, this would be the perfect chance to begin your observations of the Orionid meteor shower. But, wait for the Moon to set!

Sunday, October 21 – Be sure to be outdoors before dawn to enjoy one of the year’s most reliable meteor showers. The offspring of Comet Halley will grace the early morning hours as they return once again as the Orionid meteor shower. This dependable shower produces an average of 10-20 meteors per hour at maximum and the best activity begins before local midnight on the 20th, and reaches its best as Orion stands high to the south at about two hours before local dawn on the 21st. With the Moon nearly out of the morning picture, this is gonna’ be great!

Although Comet Halley has long since departed our Solar System, the debris left from its trail still remain scattered in Earth’s orbital path around the Sun, allowing us to predict when this meteor shower will occur. We first enter the “stream” at the beginning of October and do not leave it until the beginning of November, making your chances of “catching a falling star” even greater! These meteors are very fast, and although they are faint, it is still possible to see an occasional fireball that leaves a persistent trail.

For best success, try to get away from city lights. Facing south-southeast, simply relax and enjoy the stars of the winter Milky Way. The radiant, or apparent point of origin, for this shower will be near the red giant Alpha Orionis (Betelguese), but meteors may occur from any point in the sky. You will make your meteor watching experience much more comfortable if you take along a lawn chair, a blanket and a thermos of your favorite beverage.

Clouded out? Don’t despair. You don’t always need your eyes or perfect weather to meteor watch. By tuning an FM radio to the lowest frequency possible that does not receive a clear signal, you can practice radio meteor listening! An outdoor FM antenna pointed at the zenith and connected to your receiver will increase your chances, but it’s not necessary. Simply turn up the static and listen. Those hums, whistles, beeps, bongs, and occasional snatches of signals are our own radio signals being reflected off the meteor’s ion trail! Pretty cool, huh?

Por amour du ciel… ~Tammy

Weekly SkyWatcher’s Forecast: July 23-29, 2012

Greetings, fellow SkyWatchers! Are you ready for a week filled with alternative astronomical observing studies? If so, you’ll enjoy looking at some unusual stars and star clusters. If you want to keep things cool, then come along as we mine for lunar ice. Feeling a bit more lazy? Then kick back and enjoy the Delta Aquarid meteor shower or just step out after sunset and enjoy a splendid conjunction! It’s all here… Just head outside!

Monday, July 23 – Tonight we’ll launch our imaginations as we view the area around Mare Crisium and have a look at this month’s lunar challenge – Macrobius. You’ll find it just northwest of the Crisium shore. Spanning 64 kilometers in diameter, this Class I impact crater drops to a depth of nearly 3600 meters – about the same as many of our earthly mines. Its central peak rises up 1100 meters, and may be visible as a small speck inside the crater’s interior. Be sure to mark your lunar challenges and look for other features you may have missed before!

Now, relax and let’s talk until the Moon sets…

As we know most stars begin life in stellar nurseries and end life either alone or in very small groups as doubles or multiple stars. Tonight we can have a look at a group of young stars beginning their stellar evolution and end with an old solitary elder preparing to move on to an even “higher realm.” Open cluster IC 4665 (Right Ascension: 17 : 46.3 – Declination: +05 : 43) is easily detected with just about any optical aid about a finger-width north-northeast of Beta Ophiuchi. Discovered by Philippe Loys de Cheseaux in the mid-1700s, this 1400 light-year distant cluster consists of about 30 mixed magnitude stars all less than 40 million years of age. Despite its early discovery, the cluster did not achieve broad enough recognition for Dreyer to include it in the late 19th century New General Catalog and it was later added as a supplement to the NGC in the Index Catalog of 1908. Be sure to use low power to so see all of this large group.

About three finger-widths north-northeast of IC 4665 is a study that did make Dreyer’s catalogue – NGC 6572 (Right Ascension: 18 : 12.1 – Declination: +06 : 51). This 9th magnitude planetary is very small – but intense. Like the “Cat’s Eye” in Draco, and NGC 6210 in Hercules, this planetary can take a lot of magnification. Those with large scopes should look for a small, round, blue inner core encased is a faint shell. A challenge to find? You bet. Worth the work? Sometimes working for something makes it all the more fun!

Tuesday, July 24 – As our observing evening begins, be sure to look for one of the finest conjunctions of the year! Hovering around the waxing crescent Moon like bees drawn to a hive, you’ll find Mars to the upper right and Spica to the upper left (northwest and northeast respectively). To Spica’s upper right, you’ll find Saturn joining the show, too! This is a very “photogenic” opportunity…

With plenty of Moon to explore tonight, why don’t we try locating an area where many lunar exploration missions made their mark? Binoculars will easily reveal the fully disclosed areas of Mare Serenitatis and Mare Tranquillitatis, and it is where these two vast lava plains converge that we will set our sights. Telescopically, you will see a bright “peninsula” westward of where the two conjoin which extends toward the east. Just off that look for bright and small crater Pliny. It is near this rather inconspicuous feature that the remains Ranger 6 lie forever preserved where it crashed on February 2, 1964.

Unfortunately, technical errors occurred and it was never able to transmit lunar pictures. Not so Ranger 8! On a very successful mission to the same relative area, this time we received 7137 “postcards from the Moon” in the last 23 minutes before hard landing. On the “softer” side, Surveyor 5 also touched down near this area safely after two days of malfunctions on September 10, 1967. Incredibly enough, the tiny Surveyor 5 endured temperatures of up to 283 degrees F, but was able to spectrographically analyze the area’s soil… And by the way, it also managed to televise an incredible 18,006 frames of “home movies” from its distant lunar locale.

Wednesday, July 25 – Today in 1971, Apollo 15 was launched on its way towards the Moon, and we’ll continue our celebration of space exploration and walk on the Moon where the first man set foot. For SkyWatchers, the dark round area you see on the northeastern limb is Mare Crisium and the dark area below that is Mare Fecunditatis. Now look mid-way on the terminator for the dark area that is Mare Tranquillitatis. At its southwest edge, history was made.

In binoculars, trace along the terminator where the Caucasus Mountains stand – and then south for the Apennines and the Haemus Mountains. As you continue towards the center of the Moon, you will see where the shore of Mare Serenitatis curves east, and also the bright ring of Pliny. Continue south along the terminator until you spot the small, bright ring of Dionysius along the edge of Mare Tranquillitatis. Just to the southwest, you may be able to see the soft rings of Sabine and Ritter. It is near here where the base section of the Apollo 11 landing module – Eagle – lies forever enshrined in “magnificent desolation.”

For telescope users, the time is now to power up! See if you can spot small craters Armstrong, Aldrin and Collins just east. Even if you cannot, the Apollo 11 landing area is about the same distance as Sabine and Ritter are wide to the east-southeast. Even if you don’t have the opportunity to see it tonight, take the time during the next couple of days to point it out to your children, grandchildren, or even just a friend… The Moon is a spectacular world and we’ve been there!
Tonight let’s have a look with our eyes first at Delta Ophiuchi. Known as Yed Prior (“The Hand”), look for its optical double Epsilon to the southeast: Yed Posterior. Now have a look in binoculars or a telescope at absolute minimum power for another undiscovered gem…

Delta Ophiuchi is 170 light-years from us, while Epsilon is 108 – but look at the magnificent field they share. Stars of every spectral type are in an area of sky which could easily be covered by a small coin held at arm’s length. Enjoy this fantastic field – from the hot, blue youngsters to the old red giants!

Thursday, July 26 – Long before the Sun sets, look for the Moon to appear in the still-blue sky. As it darkens, watch for shadows on the surface. Have you ever wondered if there was any place on the lunar surface that hasn’t seen the sunlight? Then let’s go searching for one tonight…

Our first order of business will be to identify crater Albategnius. Directly in the center of the Moon is a dark floored area known as Sinus Medii. South of it will be two conspicuously large craters – Hipparchus to the north and ancient Albategnius to the south. Trace along the terminator toward the south until you have almost reached its point (cusp) and you will see a black oval. This normal looking crater with the brilliant west wall is equally ancient crater Curtius. Because of its high southern latitude, we shall never see the interior of this crater – and neither has the Sun! It is believed that the inner walls are quite steep and that Curtius’ interior has never been illuminated since its formation billions of years ago. Because it has remained dark, we can speculate that there may be “lunar ice” pocketed inside its many cracks and rilles that date back to the Moon’s formation!

Because our Moon has no atmosphere, the entire surface is exposed to the vacuum of space. When sunlit, the surface reaches up to 385 K, so any exposed “ice” would vaporize and be lost because the Moon’s gravity cannot hold it. The only way for “ice” to exist would be in a permanently shadowed area. Near Curtius is the Moon’s south pole, and the Clementine spacecraft’s imaging showed around 15,000 square kilometers in which such conditions could exist. So where did this “ice” come from? The lunar surface never ceases to be pelted by meteorites – most of which contain water ice. As we know, many craters were formed by just such impacts. Once hidden from the sunlight, this “ice” could remain for millions of years!

Friday, July 27 – Tonight let’s skip the Moon and take a look at an astounding system called 36 Ophiuchi, located about a thumb’s width southeast of Theta. Situated in space less than 20 light-years from Earth, even small telescopes can split this pair of 5th magnitude K type giants very similar to our own Sun, and larger telescopes can also pick up the C component as well. 36 Ophiuchi B is also known as system 544…because it has what could very likely be a planet in a habitable zone!

Now we’ll have a look at a beautifully contrasting pair of stars – Zeta 1 and 2 Scorpii. You’ll find them a little less than a handspan south-southeast of Antares and at the western corner of the J of the constellation’s shape.

Although the two Zetas aren’t a true physical pair, they are nonetheless interesting. The easternmost, orange sub-giant Zeta 2 appears far brighter for a reason… It’s much closer at only 155 light-years away. But, focus your attention on western Zeta 1. It’s a blue supergiant that’s around 5700 light-years away and shines with the light of 100,000 suns and exceeds even Rigel in sheer power! The colorful pair is easily visible as two separate stars to the unaided eye, but a real delight in binoculars or a low power telescope field. Check them out tonight!

Saturday, July 28 – Tonight let’s continue our studies of the lunar poles by returning to previous study crater Plato. North of Plato you will see a long horizontal area with a gray floor – Mare Frigoris. North of it you will note a double crater. This elongated diamond-shape is Goldschmidt and the crater which cuts across its western border is Anaxagoras. The lunar north pole isn’t far from Goldschmidt, and since Anaxagoras is just about one degree outside of the Moon’s theoretical “arctic circle” the lunar sun will never go high enough to clear the southernmost rim.

On March 5, 1998, NASA announced that Lunar Prospector’s neutron spectrometer data showed that water ice had been discovered at both lunar poles. The first results showed the ice was mixed in with lunar regolith (soil, rocks and dust), but long term data confirmed near pure pockets hidden beneath about 40 cm of surface material – with the results being strongest in the northern polar region. It is estimated there may be as much as 6 trillion kg (6.6 billion tons) of this valuable resource! If this still doesn’t get your motor running, then realize that without it, we could never establish a manned lunar base because of the tremendous expense involved in transporting our most basic human need – water.

The presence of lunar water could also mean a source of oxygen, another vital material we need to survive! And for returning home or voyaging further, these same deposits could provide hydrogen which could be used as rocket fuel. So as you view Anaxagoras tonight, realize that you may be viewing one of mankind’s future “homes” on a distant world!

Now grab a comfortable seat because the Delta Aquarid meteor shower reaches its peak tonight. It is not considered a prolific shower, and the average fall rate is about 25 per hour – but who wouldn’t want to take a chance on observing a meteor about every 4 to 5 minutes? These travelers are considered to be quite slow, with speeds around 24 kilometers per second and are known to leave yellow trails. One of the most endearing qualities of this annual shower is its broad stream of around 20 days before and 20 days after peak. This will allow it to continue for at least another week and overlap the beginning stages of the famous Perseids.

The Delta Aquarid stream is a complicated one, and a mystery not quite yet solved. It is possible that gravity split the stream from a single comet into two parts, and each may very well be a separate stream. One thing we know for certain is they will seem to emanate from the area around Capricornus and Aquarius, so you will have best luck facing southeast and getting away from city lights. Although the Moon will interfere, just relax and enjoy a warm summer night. It’s time to catch a “falling star!”

Sunday, July 29 – Tonight let’s take an entirely different view of the Moon as we do a little “mountain climbing!” The most outstanding feature on the Moon will be the emerging Copernicus, but since we’ve delved into the deepest areas of the lunar surface, why not climb to some of its peaks?

Using Copernicus as our guide, to the north and northwest of this ancient crater lie the Carpathian Mountains, ringing the southern edge of Mare Imbrium. As you can see, they begin well east of the terminator, but look into the shadow! Extending some 40 kilometers beyond the line of daylight, you will continue to see bright peaks – some of which reach 2072 meters high! When the area is fully revealed tomorrow, you will see the Carpathian Mountains eventually disappear into the lava flow that once formed them. Continuing onward to Plato, which sits on the northern shore of Imbrium, we will look for the singular peak of Pico. It is between Plato and Mons Pico that you will find the scattered peaks of the Teneriffe Mountains. It is possible that these are the remnants of much taller summits of a once stronger range, but only around 1890 meters still survives above the surface.

Time to power up! Lather, rinse and repeat until you know these by heart… To the west of the Teneriffes, and very near the terminator, you will see a narrow series of hills cutting through the region west-southwest of Plato. This is known as the Straight Range – Montes Recti – and some of its peaks reach up to 2072 meters. Although this doesn’t sound particularly impressive, that’s over twice as tall as the Vosges Mountains in central Europe and on the average very comparable to the Appalachian Mountains in the eastern United States. Not bad!

Now head about a palm’s width east of our previous study star – Zeta Scorpii – for lovely Theta. Named Sargas, this 1.8 magnitude star resides around 650 light-years distant in a very impressive field of stars for binoculars or a small telescope. While all of these are only optical companions, the field itself is worth a look – and worth remembering for the future.

About three fingerwidths north is true double Lambda Scorpii, also known as Shaula (The Sting). As the brightest known star in its class, 1.6 magnitude Lambda is a spectroscopic binary which is also a variable of the Beta Canis Majoris type, changing ever so slightly in little more than 5 hours. Although we can’t see the companion star, nearby is yet another that will make learning this starhop “marker” worth your time.

Until next week? Ask for the Moon, but keep on reaching for the stars!

Weekly SkyWatcher’s Forecast: June 25 – July 1, 2012

Greetings, fellow SkyWatchers! What a great week to enjoy lunar features! We’ll celebrate many famous birthdays – including Charles Messier – and take on challenging double stars. If you’re in the mood to just kick back in a lawn chair and enjoy, then check out the June Draconid meteor shower. (sssssh… it may have been responsible for the Tunguska Blast!) Still more? Then keep an eye on the western horizon, because Mercury is about to become a “guest star” in the Beehive Cluster! When ever you’re ready, just meet me in the back yard…

Monday, June 25 – Today celebrates the birth of Hermann Oberth – who has often been considered the father of modern rocketry. Born in Transylvania in 1894, Oberth was a visionary who was convinced space travel would one day be possible. Inspired by the works of Jules Verne, Oberth studied rockets and wrote many books devoted to the possibility of achieving spaceflight. He was the first to conceive of rocket “stages” – allowing vehicles to expend their fuel and lose dead weight. But tonight you won’t need one of Oberth’s rockets to travel to the Moon, as take on another challenge as we look mid-way along the terminator at the west shore of Mare Tranquillitatis for crater Julius Caesar.

This is also a ruined crater, but it met its demise not through lava flow – but from a cataclysmic event. The crater is 88 kilometers long and 73 kilometers wide. Although its west wall still stands over 1200 meters high, look carefully at the east and south walls. At one time, something plowed its way across the lunar surface, breaking down Julius Caesar’s walls and leaving them to stand no higher than 600 meters at the tallest. While visiting the “Tranquil Sea”, look for the unusually shaped crater Hypatia. Can you spot its rima on the southern shore of Tranquillitatis? Perhaps the bright pockmark of Moltke on its north edge will help. Hypatia sits on the northern shore of a rugged area known as Sinus Asperitatis. Do you see Alfraganus on the terminator? Follow the terrain to Theophilus and look west for Ibyn-Rushd with crater Kant to the northwest and the beautiful peak of Mons Penck to its east.

Tuesday, June 26 – On this day in 1949, asteroid Icarus was discovered on a 48-inch Schmidt plate made nine months after that telescope went into operation, and just prior to the beginning of the multi-year National Geographic-Palomar Sky Survey. The asteroid was found to have a highly eccentric orbit and a perihelion distance of just 27 million kilometers, closer to the Sun than Mercury, giving it its unusual name. It was just 6.4 million kilometers from Earth at the time of discovery, and variations in its orbital parameters have been used to determine Mercury’s mass and test Einstein’s theory of general relativity.

But, today is even more special because it is the birthday of none other than Charles Messier, the famed French comet hunter. Born in 1730, Messier is best known for cataloging the 100 or so bright nebulae and star clusters that we now refer to as the Messier objects. The catalog was intended to keep both Messier and others from confusing these stationary objects with possible new comets.

] If you missed your chance last night to see the incredible Alpine Valley, it’s now fully disclosed in the sunlight. Viewable through binoculars as a thin, dark line, telescopic observers at highest powers will enjoy a wealth of details in this area, such as a crack running inside its boundaries. It’s a wonderful lunar observing challenge and a guide to our next lunar feature – Cassini and Cassini A. Where the valley joins the lunar Alps, follow the range south into Mare Imbrium. Along the way you will see the protruding bright peaks of Mons Blanc, Promontorium DeVille, and at the very end, Promontorium Agassiz ending in the smooth sands. Southeast of Agassiz you will spot Cassini. The major crater spans 57 kilometers and reaches a floor depth of 1240 meters. The challenge is to also spot the central crater A, which is only 17 kilometers wide, yet drops down another 2830 meters below the surface. This shallow crater holds another challenge within – Cassini A. But look carefully, can you spot the B crater on Cassini’s inner southwestern rim? Or the very small M crater just outside the northern edge?

For more advanced lunar observers, head a bit further south to the Haemus Mountains to look for the bright punctuation of a small crater on the southwest shore of Mare Serenitatis. Increase your magnification and look for a curious feature with an even more curious name… Rima Sulpicius Gallus. It is nothing more than a lunar wrinkle which accompanies the crater of the same name – a long-gone Roman counselor. Can you trace its 90 kilometer length?

Now see how many Messier objects that you can capture and wish Charles a happy birthday!

Wednesday, June 27 – Let’s begin our lunar studies tonight with a little “mountain climbing!” Using Copernicus as our guide, to the north and northwest of this ancient crater lie the Carpathian Mountains ringing the southern edge of Mare Imbrium. As you can see, they begin well east of the terminator, but look into the shadow! Extending some 40 kilometers beyond the line of daylight, you will continue to see bright peaks – some of which reach a height of 2072 meters. When the area is fully revealed tomorrow, you will see the Carpathian Mountains disappear into the lava flow that once formed them.

Let’s try looking just south of Sinus Medii and identifying these features: (1) Flammarion, (2) Herschel, (3) Ptolemaeus, (4) Alphonsus, (5) Davy, (6) Alpetragius, (7) Arzachel, (8) Thebit, (9) Purbach, (10) Lacaille, (11) Blanchinus, (12) Delaunay, (13) Faye, (14) Donati, (15) Airy, (16) Argelander, (17) Vogel, (18) Parrot, (19) Klein, (20) Albategnius, (21) Muller, (22) Halley, (23) Horrocks, (24) Hipparchus, (25) Sinus Medii

When skies are dark, it’s time to have a look at the 250 light-year distant silicon star Iota Librae. This is a real challenge for binoculars – but not because the components are so close. In Iota’s case, the near 5th magnitude primary simply overshadows its 9th magnitude companion! In 1782, Sir William Herschel measured them and determined them to be a true physical pair. Yet, in 1940 Librae A was determined to have an equal magnitude companion only .2 arc seconds away…. And the secondary was proved to have a companion of its own that echoes the primary. A four star system!

While you’re out, keep watch for a handful of meteors originating near the constellation of Corvus. The Corvid meteor shower is not well documented, but you might spot as many as ten per hour.

Thursday, June 28 – Tonight on the lunar surface, use crater Copernicus as a guide and look north-northwest to survey the Carpathian Mountains. The Carpathians ring the southern edge of Mare Imbrium beginning well east of the terminator. But let’s look on the dark side. Extending some 40 km beyond into the Moon’s own shadow, you can continue to see bright peaks – some reaching 2000 meters high! Tomorrow, when this area is fully revealed, you will see the Carpathians begin to disappear into the lava flow forming them. Continuing northward to Plato – on the northern shore of Mare Imbrium – re-identify the singular peak of Pico. Between Plato and Mons Pico you will find the many scattered peaks of the Teneriffe Mountains. It is possible that these are the remnants of much taller summits of a once precipitous range. Now the peaks rise less than 2000 meters above the surface.

Time to power up! West of the Teneriffes, and very near the terminator, you will see a narrow line of mountains, very similar in size to the Alpine Valley. This is known as the Straight Range or the Montes Recti. To binoculars or small scopes at low power, this isolated strip of mountains will appear as a white line drawn across the grey mare. It is believed this feature may be all that is left of a crater wall from the Imbrium impact. It runs for a distance of around 90 kilometers, and is approximately 15 kilometers wide. Some of its peaks reach as high as 2072 meters! Although this doesn’t sound particularly impressive, that’s over twice as tall as the Vosges Mountains in west-central Europe, and on the average very comparable to the Appalachian Mountains in the eastern United States.

When you’re finished with your lunar observations, tonight let’s try a challenging double star – Upsilon Librae. This beautiful red star is right at the limit for a small telescope, but quite worthy as the pair is a widely disparate double. Look for the 11.5 magnitude companion to the south in a very nice field of stars!

Friday, June 29 – Today we celebrate the birthday of George Ellery Hale, who was born in 1868. Hale was the founding father of the Mt. Wilson Observatory. Although he had no education beyond his baccalaureate in physics, he became the leading astronomer of his day. He invented the spectroheliograph, coined the word astrophysics, and founded the Astrophysical Journal and Yerkes Observatory. At the time, Mt. Wilson dominated the world of astronomy, confirming what galaxies were and verifying the expanding universe cosmology, making Mt. Wilson one of the most productive facilities ever built. When Hale went on to found Palomar Observatory, the 5-meter (200?) telescope was named for him and dedicated on June 3, 1948. It continues to be the largest telescope in the continental United States.

It’s time to head deeper toward the lunar south as we take a close look at the dark, heart-shaped region Palus Epidemiarum. Caught on its southern edge is the largely eroded Campanus with well defined Cichus to the east and Ramsden to the west. Power up in your telescope and look carefully at its smooth floors. If conditions are favorable, you will catch Rima Hesiodus cutting across its northern boundary and the crisscross pattern of Rima Ramsden in the western lobe. Can you make out a small, deep puncture mark to the northeast? It might be small, but it has a name – Marth.
Now let’s go deep south and have look at an area which once held something almost half a bright as tonight’s Moon and over four times brighter than Venus. Only one thing could light up the skies like that – a supernova. According to historical records from Europe, China, Egypt, Arabia and Japan, 1001 years ago the very first supernova event was noted. Appearing in the constellation of Lupus, it was at first believed to be a comet by the Egyptians, yet the Arabs saw it as an illuminating “star.”

Located less than a fingerwidth northeast of Beta Lupus (RA 15 02 48.40 Dec -41 54 42.0) and a half degree east of Kappa Centaurus, no visible trace is left of a once grand event that spanned five months of observation beginning in May, and lasting until it dropped below the horizon in September, 1006. It is believed all the force created from the event was converted to energy and very little mass remains. In the area, a 17th magnitude star shows a tiny gas ring and radio source 1459-41 remains our best candidate for pinpointing this incredible event.

Saturday, June 30 – We start our observing evening with the beautiful Moon as we return first to the ancient and graceful landmark crater Gassendi standing at the north edge of Mare Humorum. The mare itself is around the size of the state of Arkansas and is one of the oldest of the circular maria on the visible surface. As you view the bright ring of Gassendi, look for evidence of the massive impact which may have formed Humorum. It is believed the original crater may have been in excess of 462 kilometers in diameter, indenting the lunar surface almost twice over. Over time, similar smaller strikes formed the many craters around its edges and lava flow gradually gave the area the ridge- and rille-covered floor we see tonight. Its name is the “Sea of Moisture,” but look for its frozen waves in the long dry landscape.

Caught on the north-western rim of Mare Humorum, look for crater Mersenius. It is a typical Nectarian geological formation, spanning approximately 51 miles in diameter in all directions. Power up in a telescope to look for fine features such as steep slopes supporting newer impact crater Mersenius P and tiny interior craterlet chains. Can you spot white formations and crevices along its terraced walls? How about Rimae Mersenius? Further south you’ll spy tiny Liebig helping to support Mersenius D’s older structure, along with its own small set of mountains known as the Rupes Liebig. Continue to follow the edge of Mare Humorum around the wall known as Rimae Doppelmayer until you reach the shallow old crater Doppelmayer. As you can see, the whole floor fractured crater has been filled with lava flow from Mare Humorum’s formation, pointing to an age older than Humorum itself. Look for a shallow mountain peak in its center – there’s a very good chance this peak is actually higher than the crater walls. Did this crater begin to upwell as it filled? Or did it experience some volcanic activity of its own? Take a closer look at the floor if the lighting is right to spy a small lava dome and evidence of dark pyroclastic deposits – it’s a testament to what once was!

Still got the moonlight blues? Then try your hand at a super challenging double – Mu Librae. This pair is only a magnitude apart in brightness and right at the limit for a small telescope. Up the power slowly and look for the companion just to the southwest of the primary. Good luck and mark your observation because Mu’s blues are on many observing lists!

And out of the blue comes a meteor shower! Keep watch tonight for the June Draconids. The radiant for this shower will be near handle of Big Dipper – Ursa Major. The fall rate varies from 10 to 100 per hour, but tonight’s bright skies will toast most of the offspring of comet Pons-Winnecke. On a curious note, today in 1908 was when the great Tunguska impact happened in Siberia. A fragment of a comet, perhaps?

Sunday, July 1 – Today In 1917, the astronomers at Mt. Wilson were celebrating as the 100? primary mirror arrived. Up until that time, the 60? Hale telescope (donated by George Hale’s father) was the premier creation of St. Gobrain Glassworks – which was later commissioned to create the blank for the Hooker telescope. Thanks to the funds provided by John D. Hooker (and Carnegie), the dream was realized after years of hard work and ingenuity to create not only a building to properly house it – but the telescope workings as well. It saw “first light” five months later on November 1.
As anxious astronomers waited for this groundbreaking moment, the scope was aimed at Jupiter but the image was horrible – to their dismay, workmen had left the dome open and the Sun had heated the massive mirror! Try as they might to rest until it had cooled – no astronomer slept. Fearful of the worst, sometime around three in the morning they returned again long after Jupiter had set. Pointing the massive scope towards a star, they achieved a perfect image!

If you’re looking for a perfect image, then look no further than the western horizon tonight at twilight. Why? Because Mercury is going to be a “guest star” in the Beehive Cluster! Be sure to at least get out your binoculars and look at the speedy little inner planet as it cruises about a degree or so to the western edge of M44.

Tonight we’ll return again to our landmark lunar feature – crater Grimaldi – and begin our journey north…

As you move north of Grimaldi on a crater hop, the next feature you will en-counter is the walled plain of Hevelius. With a diameter of about 64 miles, this round area doesn’t have a height we can really measure because of its lunar position, but we can see that it does have some relatively steep walls around its edges. Hevelius was formed in the Nectarian geological period and if you look closely you’ll see that it has a small central peak, a fine rimae and many craterlet chains, too. Can you spot large interior Crater Hevelius A with just binoculars? How about companion crater Cavalerius which is part of its northern border?

While you’re out, take the time to look at lowly Theta Lupi about a fistwidth south-southwest of the mighty Antares. While this rather ordinary looking 4th magnitude star appears to be nothing special – there’s a lesson to be learned here. So often in our quest to look at the bright and incredible – the distant and the impressive – we often forget about the beauty of a single star. When you take the time to seek the path less traveled, you just might find more than you expected. Hiding behind a veil of the “ordinary” lies a trio of three spectral types and three magnitudes in a diamond-dust field. An undiscovered gem…

Until next week? Ask for the Moon, but keep on reaching for the stars!

Weekly SkyWatcher’s Forecast: April 23-29, 2012

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Greetings, fellow SkyWatchers! What a great week to just enjoy some great unaided eye astronomy observations. Who can resist the beautiful appearance of Mars in Leo? Also this week, you’ll enjoy not one – but two – meteor showers as the Mu Virginids come to town mid-week and the Bootids light up the weekend. Get ready to enjoy bright stars, find planets, explore lunar features, learn some astronomy history and much more! When ever you’re ready, meet me in the back yard…

Monday, April 23 – Pioneer quantum physicist Max Planck was born on this day in 1858. In 1900, Max developed the Planck equation to explain the shape of blackbody spectra (a function of temperature and wavelength of emission). A “blackbody” is any object that absorbs all incident radiation – regardless of wavelength. For example, heated metal has blackbody properties because the energy it radiates is thermal. The blackbody spectrum’s shape remains constant, and the peak and height of an emitter can be measured against it – be it cosmic background radiation – or our own bodies.

Now, let’s put this knowledge into action. Stars themselves approximate blackbody radiators, because their temperature directly controls the color we see. A prime example of a “hot” star is Alpha Virginis, better known as Spica. Compare its color to the cooler Arcturus… What colors do you see? There are other astronomical delights that radiate like blackbodies over some or all parts of the spectrum as well. You can observe a prime example in a nebula such as M42, in Orion. By examining the radio portion of the spectrum, we find the temperature properly matches that of electrons involved in the process of fluorescence. Much like a common household fixture, this process is what produces the visible light we can see.

Tuesday, April 24 – Today in 1970, China launched its first satellite. Named Shi Jian 1, it was a successful technological and research craft. This achievement made China the fifth country to send a vessel into space.

Tonight see if you can spot the tender beginnings of the Moon after sunset. Observers take pleasure in sweeping the sky with small scopes and binoculars in hopes of finding the thinnest possible lunar crescent. And speaking of crescents, did you spot Venus close to the Moon? Why not take out your telescope and see what phase Venus is now in. If you don’t have a filter to cut its bright glare, try wearing sunglasses!

No telescope? No problem. You can still do some very awesome astronomy with just your eyes! Begin with locating the northern constellation of Ursa Major – most commonly known as the “Big Dipper”. Take note of the curve of the Dipper’s “handle” and trace it from the bottom of the cup and continue on the “Arc to Arcturus”. Keep moving, because now you’re going to “Speed on to Spica”! Once you’ve located this bright, blue/white star, simply look to its east/southeast (or upper left) for a yellow appearing “star”. That’s no star… That’s Saturn!

Now let’s have a look at 140 light-year distant Epsilon Hydrae – the northernmost star in the small circlet east of Procyon. While it and Rho will make a beautiful visual double for binoculars, Epsilon itself is a multiple system. Its A and B components are a tough split for any scope, but the 8th magnitude C star is easier. The D component is a dwarf star.

Wednesday, April 25 – Today marks the 15th anniversary of the deployment of Hubble Space Telescope. While everyone in the astronomical community is well aware of what this magnificent telescope “sees,” did you know that you can see it with just your eyes? The HST is a satellite that can be tracked and observed. Visit heavens-above.com and enter your location. This page will provide you with a list of visible passes for your area. Although you can’t see details of the scope itself, it’s great fun to track with binoculars or see the Sun glinting off its surface in a scope.

Tonight our first voyage is to the Moon’s surface. Look along the terminator in the southern quadrant and revisit ancient old crater Furnerius. Named for French Jesuit mathematician George Furner, this crater spans approximately 125 kilometers and is a lunar club challenge. Power up and look for two interior craters. The smaller is crater A and it spans a little less than 15 kilometers and drops to a depth of over 1000 meters. The larger crater C is about 20 kilometers in diameter, but goes far deeper, to more than 1400 meters. That’s about as deep as a coral will grow under the Earth’s oceans!

Keep a watch on the skies while you’re out as the Mu Virginid meteor shower reaches its peak at 7 to 10 per hour. With dark skies tonight, you still might catch one of these medium speed meteors radiating from a point near the constellation of Libra.

Thursday, April 26 – On this date in 1920, the Shapely-Curtis debate raged in Washington on the nature of and distance to spiral nebulae. Shapely claimed they were part of one huge galaxy to which we all belonged, while Curtis maintained they were distant galaxies of their own. Thirteen years later on the same date, Arno Penzias was born. He went on to become a Nobel Prize winner for his part in the discovery of the cosmic microwave background radiation, through searching for the source of the “noise” coming from a simple horn antenna. His discovery helped further our understanding of cosmology in ways that Shapely and Curtis could have never dreamed of.

Perhaps they dreamed of Moon? We’ve got Moon! No matter, what we really want to do is revisit and study a changeable, sometimes transient, and eventually bright feature on the lunar surface – crater Proclus. At around 28 kilometers in diameter and 2400 meters deep, Proclus will appear on the terminator on the west mountainous border of Mare Crisium. For many viewers tonight, it will seem to be about 2/3 black, but 1/3 of the exposed crater will be exceptionally brilliant – and with good reason. Proclus has an albedo, or surface reflectivity, of about 16%, which is an unusually high value for a lunar feature. Watch this area over the next few nights as two rays from the crater will widen and lengthen, extending approximately 322 kilometers to both the north and south. Congratulations on another lunar club challenge!

Friday, April 27 – Tonight we’re heading towards the lunar surface to view a very fine old crater on the northwest shore of Mare Nectaris – Theophilus. Slightly south of mid-point on the terminator, this crater contains an unusually large multiple-peaked central mountain which can be spotted in binoculars. Theophilus is an odd crater, one that is a parabola – with no area on the floor being flat. It stretches across a distance of 100 kilometers and dives down 440 meters below the surface. Tonight it will appear dark, shadowed by its massive west wall, but look for sunrise on its 1400 meter summit!

Now, let’s try picking up a globular cluster in Hydra that is located about 3 fingerwidths southeast of Beta Corvus and just a breath northeast of double star A8612 – M68 (Right Ascension:12 : 39.5 – Declination: -26 : 45). This class X globular was discovered in 1780 by Charles Messier and first resolved into individual stars by William Herschel in 1786. At a distance of approximately 33,000 light-years, it contains at least 2000 stars, including 250 giants and 42 variables. It will show as a faint, round glow in binoculars, and small telescopes will perceive individual members. Large telescopes will fully resolve this small globular to the core!

While you’re out, have a look at 27 Hydrae about a fingerwidth southwest of Alpha. It’s an easy double for any equipment with its slightly yellow 5th magnitude primary and distant, white, 7th magnitude secondary. Although it is wide, the pair is a true binary system.

Saturday, April 28 – Today was a very busy day in astronomy history. Newton published his Principia in 1686 on April 28. In 1774, Francis Baily was born. He went on to revise star catalogs and explain the phenomenon at the beginning and ending of a total solar eclipse which we know as “Baily’s Beads.” 1900 saw the birth of Jan Hendrick Oort, who quantified the Milky Way’s rotation characteristics and envisioned the vast, spherical area of comets outside our solar system that we now call the Oort Cloud. Last, but not least, was the birth of Bart Jan Bok in 1906 who studied the structure and dynamics of the Milky Way.

Tonight’s outstanding lunar feature will be crater Maurolycus just southwest of the three rings of Theophilus, Cyrillus and Catharina. This lunar club challenge spans 114 kilometers and goes below the lunar surface by 4730 meters. Be sure to look for Gemma Frisius just to its north.

Now let’s check out a dandy little group of stars that are about a fistwidth southeast of Procyon and just slightly more than a fingerwidth northeast of M48. Called C Hydrae, this group isn’t truly gravitationally bound, but is a real pleasure to large binoculars and telescopes of all sizes. While they share similar spectral types, this mixed magnitude collection will be sure to delight you!

For SkyWatchers, no equipment is necessary to enjoy the Alpha Bootid meteor shower – despite the Moon. Pull up a comfortable seat and face orange Arcturus as it climbs the sky in the east. These slow meteors have a fall rate of 6 to 10 per hour and leave very fine trails, making an evening of quiet contemplation most enjoyable.

Sunday, April 29 – Before we explore space, let’s have a look at the Moon and the close apparition of Regulus and Mars! The three make a wonderful “line up” the night sky! Now, let’s start our lunar observations tonight as challenge craters Cassini and Cassini A come into view just south of the black slash of the Alpine Valley. The major crater spans 57 kilometers and reaches a floor depth of 1240 meters. The challenge is to also spot the central crater A, which is only 17 kilometers wide, yet drops down another 2830 meters below the surface.

While we’re out, have a look at R Hydrae about a fingerwidth east of Gamma – which is a little more than fistwidth south of Spica. R is a beautiful, red, long-term variable first observed by Hevelius in 1662. Located about 325 light-years from us, it’s approaching – but not that fast. Be sure to look for a visual companion star as well!

Until next week? Dreams really do come true when you keep on reaching for the stars!

Many thanks to John Chumack of Galactic Images for his outstanding photo of “Leo In Mars”!