The Sky This Week – June 5 – 12, 2018 !

The Sky This Week, 2018 June 5 – 12

Hanging with Hercules
Globular
Globular cluster Messier 13 in Hercules
Imaged on 2016 August 23 from Fishers Island, New York
with a 10.2-cm (4-inch) f/6.5 AR102 refractor and a Canon EOS Rebel T2i DSLR.

The Moon greets early risers this week, waning through her crescent phases as she begins to climb northward on the ecliptic through the rising constellations of autumn.  New Moon occurs on June 13th at 3:43 pm Eastern Daylight Time.  Luna is a lonely traveler this week, passing near no bright objects during the course of her journey.

Despite their short duration, nights in June can often be quite pleasant for skywatching, and they can also be quite clear.  This offers us a chance to enjoy transparent nights that are generally free from the haze and humidity that will inevitably descend on us in July and August.  This clarity and the absence of the Moon make it a good week to make some observations for the Globe at Night citizen-science project.  The goals of this program are two-fold: on the one hand it’s an attempt to quantify the visibility of celestial objects from a variety of viewing locations while on the other it’s a chance to bring more people into the sphere of amateur astronomy.  This month the featured constellation is Hercules, which can be found in the area between the bright stars Arcturus and Vega.  Hercules has no stars brighter than second magnitude, so it can be a challenge to observe from densely lit urban areas.  It’s most prominent feature is a quadrilateral asterism that is popularly known as The Keystone which lies about a third of the distance from Vega to Arcturus.  I can just see this group from my urban back yard, but the further I move from the city the more stars that outline the rest of Hercules stand out.  It’s actually quite a large constellation when seen from a good rural location, and with a little imagination you might be able to trace out something that looks vaguely human, albeit he seems to be standing on his head!  Whether you see a classical Greek hero or not, the number of stars that you can see are what’s important to report to the Globe at Night project via their website.

What Hercules lacks in bright stars is made up for by the presence of two superb “deep sky” objects, the globular star clusters Messier 13 and Messier 92.  These knotted balls of hundreds of thousands of stars can be seen as fuzzy blobs of light with binoculars under dark skies.  A modest telescope of 4-inches aperture will resolve them into countless pinpoints surrounding luminous cores, and larger telescopes reveal more and more details in these wonderful objects.  Messier 13 is the finest of its type in the northern sky, and Messier 92 would be a “showpiece” object if it weren’t located so close to M13 in the sky.  There are about 150 globular clusters in the Milky Way galactic system.  They are made up of very old stars and may be the cores of primordial “dwarf galaxies” that were consumed by our much larger galactic home.  They follow long looping orbits around the Milky Way’s center, which is why we see them predominantly in the summer sky.  Their cores are densely packed with stars which occasionally lead to stellar collisions.  Such events produce a very unusual type of star known as a “blue straggler”.

Closer to home we find the dazzling planet Venus dominating the western twilight and early evening sky.  Her eastward motion will take her past the Twin Stars of Gemini, Castor and Pollux, over the course of the week.  She forms a straight line with the stars on the evening of the 10th.  By the week’s end Venus begins to cross the faint constellation of Cancer, the Crab.

Jupiter appears high in the southeast as evening twilight fades and offers owners of small telescopes many hours of enjoyable viewing.  You don’t need a large telescope to get something out of looking at the giant planet since his four bright Galilean moons are visible with a simple spotting scope.  There will be an unusual configuration of the moons on the evening of the 7th.  Fromm 11:10 pm EDT until 12:20 am you’ll only see two of the moons.  Io will then emerge from the planet’s shadow at 12:20 am, and at 12:56 am Ganymede will pop out of the shadow well to the east of the planet.

Saturn joins the planet parade in the late evening hours, climbing into the southeastern sky after 10:00 pm.  His yellow hue may be found just above the top of the “Teapot” asterism of Sagittarius

Mars is still best seen in the morning twilight.  The red planet crosses the meridian in the south at around 5:00 am along with the faint stars of the constellation Capricornus.  Mars is steadily increasing in brightness, and his telescopic disc is now becoming easier to define inn modest telescopes.  Early morning skies tend to be very steady for planetary viewing, so if you’re up early give him a look with the telescope.

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The Sky This Week, May 22 – 29, 2018 !

The Sky This Week, 2018 May 22 – 29

Bright Moon washing out the sky? No problem…
Scoping
Observing the Moon with USNO’s 1895-vintage
30.5-cm (12-inch) f/15 Clark/Saegmüller refractor

The Moon waxes in the evening sky this week, diving southward along the ecliptic as her phase increases.  Full Moon occurs on the 29th at 10:19 am Eastern Daylight Time.  May’s Full Moon has popular names that incorporate the pleasant climate of late spring.  These include the Milk Moon, Flower Moon, and Corn Planting Moon.  Luna passes less than a degree north of the second-magnitude star Porrima in the constellation of Virgo on the evening of the 24th.  Porrima is a closely-spaced double star whose components are now slowly separating as they orbit their center of mass.  This is one of the few double stars where a significant change in separation and position angle of the components can be easily observed over a ten-year period, and it’s one that I have followed for about 30 years.  The components are almost equal in brightness and are currently about 3 arcseconds apart, so they should be visible inn a 4-inch telescope.  The stars were closest in 2005, when I could not resolve them in my 9.25-inch scope.  One night after Luna passes by Porrima she will be placed well north of Spica, the brightest star in Virgo.  On the 27th she sits just to the east of the bright planet Jupiter.

The Moon washes out many of the fainter stars of the springtime sky, but one bright star stands out in the evening no matter how much light the Moon throws at it.  Arcturus shines with the glow of a shimmering topaz high in the eastern sky as twilight deepens.  Arcturus is the brightest star in the northern hemisphere sky and the fourth brightest of all, only exceeded by Sirius and the southern hemisphere stars Canopus and Alpha Centauri.  It is relatively near to the solar system with a measured distance of just under 37 light years.  Its mass is thought to be slightly greater than that of the Sun, but its luminosity is some 170 times more than that of Old Sol.  Its age is estimated to be about 7 billion years, so Arcturus may be a good model to study the future fate of the Sun.  Arcturus is an “evolved” star that has depleted the supply of hydrogen in its core; it is now fusing hydrogen into helium in a shell around the core.  This causes the star to swell in size to about 25 times the Sun’s diameter.  As its surface expands it cools, giving the star its characteristic warm color.  It has the most rapid proper motion of all of the first-magnitude stars except the nearest, Alpha Centauri, moving about two arcseconds per year.  This means that it moves the apparent diameter of the Moon’s disc in 900 years.  Arcturus’ proper motion was discovered in 1718 by astronomer Edmond Halley, who noticed that it was far from the position measured by the Greek astronomer Hipparchus some 1800 years earlier.  The name “Arcturus” derives from ancient Greek and means “Guardian of the Bear” for its position in the sky, following the stars that form the constellation Ursa Major.  It is the lead star in the constellation of Boötes, the Herdsman, which in my mind looks more like a kite or an ice-cream cone that the ancients’ interpretation of a man with a staff holding two dogs on a leash!

As Arcturus climbs in the east, Ursa Major crosses the meridian high overhead.  The constellation’s signature asterism, the seven stars that form the “Big Dipper”, should be easy to find despite the increasing glow of light scattered from the Moon.

Bright Venus still dazzles in the western sky as evening twilight falls.  She is now coursing her way through the stars of Gemini, the Twins, and reaches her most northerly declination in this year’s evening apparition on the 22nd.  She will continue her eastward trek across the stars and will start to slowly move southward over the horizon over the course of the next few months.

Jupiter becomes visible in the southeast shortly after sunset, and he spends the evening wheeling across the sky, crossing the meridian at around 11:00 pm.  The giant planet is at his best for telescopic viewing, and you should be able to enjoy him in the telescope all night long.  In addition to looking for the planet’s signature equatorial cloud belts and Great Red Spot, watch the changes in the configurations of his four bright Galilean moons.  On the evening of the 23rd watch his innermost large moon Io drag its shadow across the planet’s disc between 9:13 and 11:23 PM EDT.

Look for Saturn low in the southeast during the late evening hours.  Saturn spends most of the next several months in the vicinity of the top of the “Teapot” asterism of Sagittarius and is near the most southerly declination in his 29-year orbit.  Wait for a night with steady air to get a good glimpse of the ringed planet.

Mars is beginning to slow his eastward progress among the faint stars of Capricornus as he nears the first stationary point of this year’s apparition, which he’ll reach next month.  Like Saturn, he will spend this year’s apparition at a very southerly declination, so nights of steady air will give you the best views of his growing, ruddy disc.  Your best view of him this week continues to be in the hours before dawn.

The Sky This Weel, May 8 – 15 2018 !

The Sky This Week, 2018 May 8 – 15

A look into the deep…
Markarian's Chain
“Markarian’s Chain”, the heart of the Virgo Galaxy Cluster, 2013 April 14,
imaged from Vaucluse, Virginia with a 80-mm (3.1-inch) f/6 Antares Sentinel refractor and a Canon EOS Rebel T2i DSLR

The Moon wanes in the pre-dawn sky this week, passing through the dim constellations as she slips through her crescent phases before disappearing in the glow of twilight.  New Moon occurs on the 15th at 7:48 am Eastern Daylight Time.

The nights of May grow shorter as the Sun continues to climb northward along the ecliptic.  Sunset now occurs well after 8:00 pm, which means that the end of evening astronomical twilight now falls at around 10:00 pm.  Morning astronomical twilight begins shortly after 4:00 am, so we now have just six hours to enjoy a fully dark sky.  Fortunately May evenings can be quite mild, and with the Moon moving into the early morning sky it’s a great time to explore the “deep sky” well beyond the bounds of our Milky Way galaxy.  In fact, if you were to look for the luminous band that defines the plane of the Milky Way you will find it confined to the horizon.  This means that as we look out into the space between the bright stars Arcturus, Spica, and Denebola (the “tail” of Leo, the Lion) we are looking through a thin veil of nearby stars across a vast gulf of intergalactic space several tens of millions of light-years deep.  Populating this region beyond the Milky Way’s stars brings us to hundreds of faint fuzzy swatches of light that betray entire galaxies like ours sprinkled across an enormous volume of space.  A modest telescope of 8-inches will show dozens of these misty patches within the three-star boundary, and larger instruments will reveal hundreds more.  All of these galaxies are associated with each other in a huge gravitationally-bound grouping known as the Virgo Cluster.  Astronomers recognize about 1500 galaxies in the cluster, most of which lie at a distance of over 50 million light-years.  Several of the galaxies near the center of the cluster are truly gigantic, with masses estimated at trillions of Suns!  The influence of the cluster is far-reaching, and its gravity even influences the motions of the galaxies in our “Local Group”, including our Milky Way!

Closer to home, the last of the winter stars are setting at 10:00 pm.  The last to settle below the horizon are Castor and Pollux, the Twin Stars of Gemini.  They are now replaced by lesser lights: where the Great Winter Circle contains nine first-magnitude stars, our current sky only hosts three.  These three stars, Arcturus, Spica, and Regulus, lead large scattered groupings of fainter stars that make up the constellations Boötes, Virgo, and Leo.  Of these, only Leo bears a passing resemblance to its namesake.  The most prominent springtime asterism, the “Big Dipper” portion of Ursa Major, contains no first-magnitude stars at all, but fortunately all but one of its seven stars are second-magnitude.

Venus is steadily moving eastward through the setting stars of Taurus, the Bull.  This week she passes between the Bull’s “horns”, marked by the stars Zeta Tauri and El Nath, a star “shared” with Auriga, the Charioteer.  The dazzling planet is running a pace that keeps her even with the advances of the Sun, setting about 45 minutes after the end of evening twilight.

Jupiter is now visible in the sky all night long after reaching opposition on the 8th at 9:00 pm.  This is the time when Old Jove presents his largest apparent disc diameter, and owners of small to modest telescopes should be able to glimpse his main cloud belts and the Great Red Spot when it is facing us.  His four bright Galilean moons will offer a different configuration around the planet each night and are easily visible in binoculars and small telescopes.

Saturn sits just above the top of the “Teapot” asterism of Sagittarius.  The ringed planet sits in the middle of a dense Milky Way star cloud.  He is slowly drifting westward as he approaches his opposition in late June.  Take advantage of the moonless sky to spot the bright globular star cluster Messier 22, just over a degree south of Saturn.

Ruddy Mars crosses into the faint constellation of Capricornus as he continues to move eastward along the ecliptic.  His distinctive pink hue is unmistakable in this barren part of the sky.  His apparent disc is steadily growing as is his brightness.  When he reaches opposition in late July his disc will be twice as big as it appears now and he will be seven times brighter.

The Sky This Week, April 17 – 24, 2018 !

The Sky This Week, 2018 April 17 – 24

Celebrate Dark-sky Week and Astronomy Day!
Crescent Moon, 2018 February 20, imaged with the USNO 12-inch telescope
Crescent Moon, 2018 February 20 @ 23:30 UT,
imaged with the USNO 30.5-cm (12-inch) f/15 Clark Saegmüller refractor
and a Canon EOS Rebel T2i DSLR, composite of nine exposures.

The Moon returns to the evening sky this week, waxing through her crescent phases as she wends her way through the setting winter constellations.  First Quarter occurs on the 22nd at 5:46 pm Eastern Daylight Time.  Luna begins the week in the company of bright Venus in the fading evening twilight on the 17th.  On the following evening she may be found just west of the bright star Aldebaran in Taurus.  If you look at her with binoculars you’ll find her embedded in the V-shaped Hyades star cluster.  Another binocular target is flanked by the Moon on the evening of the 21st.  Take your binoculars and look just to the left of the Moon for the “Beehive” star cluster.  To round out the week, Luna will cozy up to the bright star Regulus in the constellation of Leo, the Lion.

Global Astronomy Month continues with the observance of International Dark Sky Week, which runs through the evening of the 21st.  Created by then high-school student Jennifer Barlow in 2003, this week-long observance has become a centerpiece of Global Astronomy Month and culminates on Astronomy Day, April 21st.  The idea is to simply make people aware that there is more to the night sky than street lights and neon signs and to call attention to the overuse of artificial nighttime lighting.  Not only does artificial night lighting obscure our view of the stars, it interferes with the natural biology of hundreds of species, humans included.  Migratory birds are disoriented in their annual flights, marine creatures have their reproductive cycles disrupted, and our own circadian rhythms are disrupted, particularly in the production of melatonin, which is vital for the body’s ability to “recharge” itself during a good night’s sleep.  Citizen awareness of the issues may lead to the more efficient use of nighttime lighting and not only provide an economic benefit due to lower energy consumption but also bring back a better view of the night for everyone.

As we mentioned above, the 21st is Astronomy Day, a global celebration of the night sky.  Local astronomy clubs, planetariums, and public observatories will be hosting events throughout the world.  Here in the Washington, DC area, the Northern Virginia Astronomy Club will host its annual Astronomy Day Star Party at C.M. Crockett Park in Midland, Virginia from 3:00 until 11:00 pm.  This is a great opportunity to see astronomy-related demonstrations, safely observe the Sun, and see celestial sights through a variety of telescopes provided by club members.  While the park charges a nominal entry fee, all of the program activities are free.  For other events in the area, see our web page with links to other astronomy-related resources in the local area.

The evening twilight sky is where you’ll find the bright glow of Venus, which should appear shortly after local sunset.  As the sky darkens she dominates the scene and by the end of the week sets at around 10:00 pm.  She receives a visit by the slender crescent Moon on the evening of the 17th, which should provide a fine photo opportunity.

Jupiter continues to make inroads into the evening sky.  This week the giant planet rises before 9:30, and he should be easy to spot in the southeast by 11:00 pm.  Old Jove is slowly creeping westward among the stars of the obscure constellation of Libra, the Scales, inching toward the star Zubenelgenubi, the southernmost of the constellations two brightest stars.  Jupiter will reach opposition in a few more weeks, at which time he’ll be visible all night.

Saturn is located near the top of the “Teapot” asterism in the constellation of Sagittarius.  He will stay in this general area for the next few months.  Just below Saturn you’ll find a small fuzzy patch of light in your binoculars.  A modest telescope will reveal a swarm of countless faint stars that form the globular star cluster Messier 22, one of the finest objects of its type in the heavens.

Mars is now well east of Saturn, and he’ll move another several degrees further eastward this week.  Earth is closing in on the red planet as we prepare for his opposition in July.  Mars’ disc is now growing, and this week crosses the 10 arcsecond apparent diameter threshold.  This is when owners of modest telescopes should be able to start seeing details on the planet’s distant surface.

The Sky This Week, April 3 – 10, 2018 !

The Sky This Week, 2018 April 3 – 10

April is Astronomy Month…no fooling.
The Moon rising through trees
The Full Blue/Sap/Egg/Paschal Moon rising through trees, Alexandria, VA on 2018 March 31,
imaged with a Canon EOS Rebel T2i DSLR, 250mm @ f/8, HDR composite of exposures of 1/20, 1/80,1/320, and 1/640s, ISO 800.

The Moon swings low along the southern reaches of the ecliptic this week, wending her way past the morning parade of bright planets that are drifting through the summer constellations.  Last Quarter occurs on the 7th at 3:17 am Eastern Daylight Time.  Luna starts the week just to the east of bright Jupiter, then cozies up to Mars and Saturn on the morning of the 7th.  By the week’s end she moves into the dim star fields of the rising autumnal constellations.

April is Global Astronomy Month, an annual celebration of sky awareness sponsored by Astronomers Without Borders.  Celebrating “One People, One Sky”, the next few weeks will see a number of events to increase the general public’s appreciation of the universe as seen from our humble planetary home.  There are many ways to participate in the month’s activities from composing sky poetry to turning our lights to help promote a view of a darker sky.  The month incorporates International Dark Sky Week from the 15th through the 21st, and culminates in Astronomy Day, which takes place Saturday, April 21st.  On this day amateur astronomy clubs around the world will congregate at local parks with telescopes and hands-on activities to bring the stars to anyone with an interest in exploring them.  We’ll list events in the Washington, DC area as the date approaches.

Winter’s bright constellations linger in the early evening sky.  By the end of evening twilight at around 9:00 pm, you can still find Orion in the southwestern sky surrounded by the bright stars of the Great Winter Circle.  Act quickly if you want to view celestial gems like the Pleiades or the Great Orion Nebula; they both set well before midnight.  At this time look for the twin stars of Gemini, Castor and Pollux high in the west and the star Regulus in Leo to the east of the meridian.  In between these two constellations is a small group of 3rd and 4th magnitude stars that mark the location of the Zodiacal constellation of Cancer, the Crab.  The constellation itself is not much to look at, but if you point a pair of binoculars toward it you’ll see a scattered group of several dozen stars that make up the star cluster known as “The Beehive” or the “Praesepe”.  Under dark skies you can see it as a nebulous patch of light, and it was one of the first such “nebulae” to be investigated by Galileo with his primitive telescope in 1609.  He was able to resolve it into about 40 stars, and you should be able to see that many in binoculars.  Large telescopes reveal about 1000 cluster members, most of which are very low-mass red dwarf stars.  It lies about 580 light-years from us and is one of the closest large star clusters to the solar system.

As the midnight hour approaches the brighter stars of spring begin to take over the night.  Regulus and his companions in Leo are near the meridian, and the Big Dipper Asterism can be found almost directly overhead.  You can follow the arc of the Dipper’s “handle” to the bright star Arcturus, the fourth-brightest star in the sky, then “drive a spike” to Spica, the brightest star in the sprawling constellation of Virgo.

The evening twilight hour is dominated by the dazzle of the bright planet Venus, which shines high in the west.  She becomes visible within minutes of sunset in a clear sky and remains visible until after 9:00 pm.

Giant Jupiter rises at around 10:30 pm and should be easily visible in the southeast by midnight.  Old Jove is now second only to Venus in brightness and will move into better evening visibility over the course of the month.  He is currently drifting westward among the stars of another faint Zodiacal constellation, Libra, the Scales.

Early risers still get the best views of Mars and Saturn, which are currently located just above the top of the “Teapot” asterism in Sagittarius.  They start the week just over a degree apart, but over the course of the week Mars drifts eastward from the ringed planet.  They will be five degrees apart by the week’s end.  Look for a great pre-dawn photo opportunity on the morning of the 7th, when the last quarter Moon joins the planetary pair.

The Sky This Week, March 27 – April 3, 2018 !

The Sky This Week, 2018 March 27 – April 3

Moons and calendars
The Moon rising over a formation in the Garden of the Gods, Colorado Springs, Colorado
The Moon rising over a sandstone formation, Garden of the Gods, Colorado Springs, CO on 2013 March 23,
imaged with a Canon EOS Rebel T2i DSLR, 250mm @ f/1, 1/320s, ISO 200.

The Moon brightens the overnight hours as she descends the ecliptic and courses through the sparse star fields of spring.  The second Full Moon of March occurs on the 31st at 8:37 am Eastern Daylight Time.  This being the second Full Moon of the month it is often referred to as a “Blue Moon”.  Generally Blue Moons occur at intervals of about 2 years 8 months, but 2018 is unusual in having Blue Moons in both January and March.  The next one will fall on Halloween, 2020.  The next time we have two Blue Moons in the same year won’t be until the year 2037.

In addition to the name “Blue Moon”, this particular Full Moon is also known as the “Paschal Moon”.  Since it is the first Full Moon to fall after the vernal equinox, it sets the date of Easter in the Christian faith.  In Judaism, which observes a lunar calendar, the observation of Passover begins on the 15th day of the month of Nisan, which also corresponds to the appearance of the first Full Moon following the equinox.  For the most part Easter and Passover occur at the same time, but there are exceptions in the way lunar months are counted in the Hebrew Calendar.  Since a “lunar month” is about 29.5 days, 12 such months yield a year of 354 days.  The eleven extra days in the solar calendar are made up by the periodic insertion of an extra month in the calendar.  Extra months are added at intervals of from 2 to three years, depending on where the year falls in the 19-year Metonic Cycle.  Over the course of this cycle there are 12 years of 12 months and 7 years of 13 months.

The bright Moon wipes out the view of many of the springtime stars.  You can still enjoy the departing winter stars that surround Orion, but you’ll need to do this early in the evening since the westernmost stars of the Great Winter Circle now set by midnight.  There are a few bright stars to enjoy in the spring sky, though.  Regulus, the heart of Leo, the Lion, is flanked by the Moon on the evenings of the 27th and 28th.  Luna perches about just over seven degrees above Spica, the brightest star of the sprawling but faint constellation of Virgo.  The brightest star in the northern sky, Arcturus, shines brightly in the east as the night passes, climbing to a place of prominence in the early morning hours.  By midnight, look just to the north of the zenith to see the seven second-magnitude stars that make up the “Big Dipper” asterism.

Venus and Mercury gave us a really good show over the past couple of weeks, but this week Venus has lost her planetary companion to the encroaching Sun.  In just two short weeks Mercury has gone from greatest eastern elongation, when he was easily visible to the naked eye, to conjunction with the Sun, when the fleet planet passes between Earth and Old Sol and is invisible.  Venus, however, continues to climb higher into the evening sky and becomes more obvious in the west with each passing evening.  By the end of the week she sets just after the end of evening twilight.  Her journey through the sky is a lonely one.  She’s moving through the constellations of the late autumn sky and won’t encounter any bright objects until she drifts between the Pleiades and the bright star Aldebaran in late April and early May.

You should be able to spot bright Jupiter low in the southeastern sky during the late evening hours.  He now rises just before 11:00 pm and should be high enough to train the telescope toward by 1:00 am.  You’d probably want to wait until the pre-dawn hours to view him, though, since he’ll be joined by ruddy Mars and ringed Saturn.  The latter two steal the show this week, as Mars passes the more distant Saturn on the morning of April 2nd.  At this time the two planets will be just over one degree apart.  If you have a pair of binoculars and are up well before the Sun look just below and to the right of Mars.  If you see a fuzzy glow of light you’ve found Messier 22, one of the brightest globular star clusters the galaxy.

The Sky This Week, March 20 – 27, 2018 !

The Sky This Week, 2018 March 20 – 27

The Moon returns while winter’s stars depart.
The Moon, Venus, & Mercury, imaged 2018 march 18 from Alexandria, Virginia.
The Moon, Venus, & Mercury, imaged 2018 March 18, 20:05 EDT from Alexandria, Virginia
with a Canon EOS Rebel T2i DSLR, 100mm @ f/6.3, 1/30s, ISO 3200.

The first week of spring finds the waxing crescent Moon climbing along the ecliptic to a perch among the retiring stars of the winter sky.  First Quarter occurs on the 24th at 11:35 am Eastern Daylight Time.  Luna opens the week in the western sky above the bright glow of Venus.  On the 22nd she passes just to the north of the bright star Aldebaran in the constellation of Taurus, the Bull.  By the end of the week she enters the springtime sky, closing in on Regulus, lead star of the constellation of Leo, the Lion.

The Moon’s path through the sky places her at a high altitude during the phases that reveal some of her most fascinating features.  This makes it a great time to explore her many and varied landscapes.  You can use something as simple as a pair of binoculars to see the changes along the Moon’s terminator from night to night.  It was such a view that I had as a youngster that inspired me to further explore the sky.  Small telescopes offer a wonderful view at relatively low magnifications.  On nights when the atmosphere is steady you can expect to see details to a scale of about a kilometer, roughly the size of Meteor Crater east of Flagstaff, Arizona.  This may hopefully give you a sense of the scale of the features on Luna’s face.  Most of the craters you’ll see are dozens of kilometers across!

The days surrounding the equinox are the times of the year when the Sun’s apparent motion along the ecliptic reaches its maximum change in the rate of change of declination.  This means that right now we add about three minutes of daylight to that of the previous day.  Most of us really notice this change more in the spring than the fall. Since we are coming out of the long dark nights of winter.  It’s a time when I notice, in particular, the demise of the bright winter constellations.  By the time evening twilight ends you’ll see that all of the stars in the Great Winter Circle are west of the meridian, and Orion, winter’s signature star pattern, is well on his way to setting by midnight.  Winter’s bright stars are now being replaced by fainter constellations that make up the springtime sky.  There is only one star in the spring that rivals the bright beacons of Orion and his cohorts, and that star is Arcturus.  You’ll find it in the northeastern sky where it starts to climb to prominence by 10:00 pm.  Arcturus is the fourth-brightest star in the sky and the brightest in the celestial northern hemisphere.  Although it is part of the larger constellation of Boötes, the Herdsman, you’ll be hard-pressed to see much of the star pattern from urban skies.  In darker locations look for something resembling an ice-cream cone to the north of Arcturus.

The easiest springtime constellations to see under brighter skies are Leo, the Lion, and the seven-star asterism we call the Big Dipper.  You’ll find them near the meridian at local midnight.  Leo has a single first-magnitude star, Regulus, which you’ll find close to the Moon on the evenings of the 27th and 28th.  The Big Dipper doesn’t have any first-magnitude luminaries, but its distinctive outline of second-magnitude stars makes it one of the most recognized asterisms in the sky.

Venus continues to gradually climb higher in the evening twilight sky.  As the week opens you’ll find the fainter planet Mercury a few degrees to the right of the dazzling Venus.  Mercury then takes an abrupt dive toward the horizon and rapidly fades to third magnitude, leaving him almost invisible in the evening twilight.

The bright planet Jupiter now rises in the southeast shortly before midnight.  He lords over the morning sky and is high in the southwest at the onset of morning twilight.  At this time you’ll notice the summer constellation Scorpius crossing the meridian, and to the east the ruddy glow of Mars shares the limelight with Saturn.  Watch Mars close the gap with Saturn.  He’ll pass the ringed planet next week.