Near-full moon rising south of east

Event Date: June 3rd
Time: 8:30 PM

Brief

   Normally at this time of year, the Moon does not get very high when full; it reaches altitudes that a late-fall or early winter Sun does, depending on where the Moon's orbit places it relative to the ecliptic.   As shown in the image, the Moon is just hours past (east) of ascending node.  When this node is at this longitude of the ecliptic, not far from where the Sun is for the December solstice, it means that while transiting low, the Moon quickly starts gaining transit altitude as seen from our hemisphere.  Over the next 5-6 days, as it also starts to move in the part of the sky that the Sun does during our winter months, its orbit speeds up the process of it moving close to the equator.  Take a look here first, seeing it on the rise just as the Sun goes down.  Since the Moon isn't quite full yet at the time of its rise 32 minutes earlier, it slowly moves higher while the Sun is still barely above the horizon.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   Although I do not show the just-set Sun above, or the Moon when it just starts rising about 30 minutes earlier, it is enough hours before the crest of fullness that both are seen above the horizon for just minutes.  Since the Moon rises south of east and the Sun sets at almost its furthest north of west at this time of year, it means that we see the Moon for only a small number of hours.  Normally a full Moon within the few weeks of the June solstice only spends 9 1/2-10 hours above the horizon as seen from mid-northern latitudes.  Once again, the exact amount of time isn't based on our latitude alone, but the ecliptic latitude of the Moon.  Look again above, and this time to the right: when the Moon was about 90º west of where it is now about a week ago, it was almost 5 1/2º south of the ecliptic.  If you think about it, with the movement of the Moon north and south of the equator and ecliptic, there are two times [per ecliptic cycle] that it rarely gains or loses declination at all.  If you have an equatorial telescope which only tracks in right ascension, this means less "dec-tweaking"* for when the Moon moves north or south during a long time of viewing it.
 
*Many telescopes use this to keep the Moon centered north/south, and doesn't require much moving, yet very handy to have!

Mercury low at Sunset

Event Date: June 2nd
Time: 8:45 PM

Brief

   Mercury started its east-of-Sun cycle at about the same time that it reached perihelion.  As a result of that, it will dim quickly compared to the last time that it was east of the Sun in February and March.  For that excellent apparition, perihelion was near the time of greatest elongation, which happened when the Sun was still south of the celestial equator and twilight time was much shorter than this month.  By the end of this month, Mercury will be visible to the eye alone with a fair apparition.  By that time, it will already be slightly further south than the Sun, and Sunsets will be their latest of the year with a maximum civil twilight duration of nearly 40 minutes.  After that, we will lose Mercury quickly in the Sun's brightness, as it also sinks further south of the Sun.

Detailed

   Despite all the cons, we will have Mercury far enough north on the celestial dome to easily see it slowly set after the Sun until about a week before greatest elongation.  Try to pick it up with binoculars about 30 minutes after Sunset once separated far enough.  At its greatest separations from the Sun, specifically 8-10 days before greatest elongation, it will still be bright enough to pick out somewhat easily with the eye.  The first image above showed Mercury 3º above the horizon.  That sounds low, yet with a -1.5 magnitude, that is still barely visible enough to see through atmospheric pollution with minimal optical aid.  Mercury sets 42 minutes after the Sun, and that gap increases by about 5 minutes tomorrow.  With a current declination gap this evening of over 2º between the Sun and Mercury, and an almost 3 1/2º gap tomorrow, Mercury's just-post perihelion days will be some of the better to see Mercury. 
This second image to follow is a 1/2º zoom in, showing Mercury as a small, waning gibbous, of 5.2 arc-seconds.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Analemma plot since December solstice

Event Date: June 1st

Time: 3:30 PM

Brief

   Since the December solstice, the Sun has moved about 45º north in declination.  I mentioned the cycle of north and south movements of the Sun on our celestial dome based on (a) our revolution around the Sun, (b) the 23 1/2º tilt of our axis.  I am showing where the Sun is each day at the time above.  This shows nearly half of what is called the analemma, which is a figure 8 shape with one loop much larger than the other.  Find out more about the analemmatic sundial as well, linked.  It's neat to see and read about!

The altitude grid is shown to show how high the Sun is above the horizon each day; this is partly dependent on declination of the Sun.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   As I mentioned in my first journal of the blog, there would be no declination of the Sun to keep track of if there was no tilt of our axis; the Sun would be at 0º along the celestial equator at all times.  Then again, if we had a nearly-90º axis tilt the way Uranus does, declinations would be at about 180º in difference from one solstice to another, with our poles facing the Sun at the solstices.   As shown for the plot over the last few weeks, the smaller loop is starting to be outlined out.  The markers are 10 days apart.  As I talked about yesterday with the rate of declination slowing down near the time of the solstices, we see the result with the markers; they are more bunched up at two altitudes, and more spread out at the others, where the Sun is at dates closer to the equinox.

Sun approaching solstice

Event Date: May 31st
Time: 1:06(.34) PM

Brief

   We are only about three weeks from the June solstice: the summer one for our hemisphere, and winter for the southern hemisphere.  The Sun has gained several degrees of northern declination since starting this blog at the 0º mark back on March 19th.  For the first month, it moved a little more than 11º; for the second month, slightly over 8º.  So far for the start of this final month before the solstice, it has moved about 2º.  It is now only about 1 1/2º from its maximum declination, and will reach that more and more slowly as it comes closer.  During the final week, there is barely any difference at all.  Look at the ecliptic and celestial equator positioning in relation to each other.  The light-yellow line left (east) of the meridian is where the 6h/90º marks meet, for r.a. and ecliptic longitude respectively.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

Looking to the far left, where the labels for the ecliptic and celestial equator are shown for clarity, we see that they are nearly parallel at this point.  Using the celestial grid lines also, the ecliptic angles up (north) of the 10º one, labeled on the right side of the frame.  It was at that marker where the Sun was in mid-late April, depending the exact date we are talking about.  When the Sun reaches the solstice indicator, where the two grids align, it will be as far north in value as our Earth's axis tilt.
   If we think ahead, this three-month northward movement of the Sun in declination will reverse: between the solstice and September equinox.  By then, the Sun will retreat to the celestial equator.  The three months after that, the declination numerical value rate increases the way it does during the spring, with the exception of the Sun heading south instead of north, on the dome.  Finally, between the December solstice and March equinox, the numerical value changes the way it does between the June solstice and September equinox, by decreasing as the Sun moves back to the celestial equator northward.  When that finally happens, if you remember my very first entry (accessed by the date-link in the brief), we reach the astronomical new year again!

Spring Arc seen from both hemispheres

Event Date: May 30th
Time: 3:00 AM

Brief

  The Spring Arc is seen high in the sky during the late evening hours at this time of year, as seen from mid-northern latitudes.  The handle stars of the Big Dipper are very high in the north.  Arcturus on the other side of zenith is seen high in the south at a similar altitude.  Spica on the other side of the celestial equator, ends up setting first, the same way--and reason--that it rose last.  Here is a reminder of where the stars can be seen during early morning hours now before dawn, and before Spica sets.  Unlabeled Saturn is seen near Spica, less than 5º away.

Detailed

   The celestial grid is included above to further show the declinations of each star.  Spica is positioned at a good altitude early in the evening, seen from most places on Earth.  The exception is that of far-north latitudes where there isn't enough nighttime to see it long anyway; it just arcs over the horizon at latitudes just south of the arctic circle, and doesn't clear the horizon at all at latitudes close to the north pole.  The opposite holds true with Arcturus, which is a little more north than Spica is south.  As for the Dipper, the stars are circumpolar from many latitudes north, and they do not clear the horizon as seen from most southern latitudes.  For the second image, I will take us to the same latitude south as we are north: Box Hill, Australia, which I have used before, at 37º 49' S.  The time zone difference is 18 hours, being mid-evening there, for the placement of the stars. 

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

   Notice that with the exception of Alkaid, the rest of the Dipper stars are below the horizon, and none of them transit above the horizon this far south.  As for Arcturus, it is seen for only 10 hours above the horizon as seen from this latitude.  Spica is seen for 13 hours, 14 minutes-- a big contrast compared to the time durations from our latitude, where Spica is up for only about 11 hours, and Arcturus up for about 14.

Mercury & Venus: low towards Sun

Event Date: May 29th
Time: 8:30 PM

Brief

   Mercury spent nearly two months with a poor apparition west of the Sun in the morning sky: either it was very low and hard to see, or for several days, engulfed in the glare of the Sun.  For the next week, it will continue to be too low in the sky at Sunset, while the long twilight following the Sun will make Mercury nearly impossible to find before it gets too low towards the horizon.  I am showing it labeled below in the image, also for a second reason mentioned in the detailed.  As the ecliptic shows, along with Mercury's orbit, the geometry of the sky is decent enough that the planet will emerge from the Sun's glare and get reasonably high in the sky to see with the eye alone.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

   Venus is finishing its cycle east of the Sun as Mercury begins its, and seen just a few degrees away.  While the two move in different directions, with Venus in retrograde and Mercury in pro-grade, they will pass by each other closely in separation.  Unfortunately by then, both will be too hard to see.  Venus is dropping back to the ecliptic a little more each day while Mercury will approach it more slowly.  I kept Venus' orbit out of the image so it will not overlap Mercury's smaller one, yet the path of Venus can still be visualized.  The result of their paths from our point of view, will mean no occultation of Mercury by Venus, even though Mercury's angular size is currently only about 1/11th that of Venus'. 
   If skies are their clearest, your horizon is completely unobstructed and viewing the horizon from high enough up, we may beable to see Venus for only a short time this evening; it sets only 56 minutes later this evening, and less than 50 tomorrow.  By the time Venus and Mercury pass at their closest separation June 1st, the set time between the Sun and the planets is down to 30 minutes.  Have optical aid, and good luck with the skies cooperation clarity-wise!  I will include a zoom-in image that evening, which will show them just past the peak.

Venus' inferior conjunction: 8 days away

Event Date: May 28th
Time: 8:30 PM

Brief

   Have you noticed over the last two entries featuring Auriga and stars, that bright Venus is much lower to the horizon; that being, compared to the altitude at the same time on the clock as we saw it as recently as two-three weeks ago at the beginning of its retrograde?  Since then, starting mid-month, the gap between Venus and the Sun setting has shrank quickly.  This evening, Venus sets only 64 minutes after the Sun, which is seven minutes earlier than yesterday.  The gap has shrunk by 50% since May 19th, when it was two hours, seven minutes.  At the same time, apparent magnitude has only gone down to -4.0, from -4.6 in late April.  While viewing in optical aid, only 2% is illuminated.  At 56 arc-seconds illuminated, Venus' disc diameter is larger than Jupiter's at perihelion and opposition combined, which is 50 arc-seconds.

Here are the zoom-out and zoom-in views of Venus, with the latter being a 1/4º field (about 200x magnification).

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

  Venus' orbit was seen as a big loop from our perspective during the late winter and early spring months.  As a result, the ecliptic latitude northward increased.  Every December and June however, we see Venus pass one of its two nodes.  This time, next month, it is passing the descending one.  In combination with the excellent late-winter sky geometry of the western sky this year, the ecliptic latitude was part of the impressive northern declination of Venus.  Although still north of the Sun's position along the ecliptic, where Venus retrograded past about a week ago, the planet has dropped in declination, and will equal that of the Sun's at inferior conjunction.  This is why I mention crossing the descending node; it happens when Venus passes between us and the Sun and as a result, one of the biggest events of our lifetime happening for the last time while most of us on Earth today, are alive:  The Venus transit of the Sun as it will be referred to, happens only twice a century, including 2004.  The next one will not be until a little over 100 years from now.  I will reveal that exact date for then, when it happens at our location the afternoon and evening of June 5th.

Auriga's stars: Capella and how many more?

Event Date: May 27th
Time: 9:00 PM


Brief

Yesterday when showing Capella low towards the horizon near Perseus, I mentioned how we can see it a little better in the evening for awhile.  Specifically, because Capella is about halfway between the celestial equator and the north celestial pole, it spends a little over 17 hours above the horizon.  Of those 17, the star is most easily visible for about 15 of them seen from mid-northern latitudes, with the other 2+ having it low to the horizon.  The celestial grid, which I have shown with the Summer Triangle stars near the opposite part of the sky, has two stars at about the same declination, with Deneb almost exactly that of Capella.  Vega is the other, about 6º south of these other two.
Capella is shown below, with the three other bright-enough stars that make up its "diamond" shape.  I kept Venus in the image as well, about a week away from falling deep into the Sun's glare.  For Auriga, why haven't I included the stick figure you may wonder?  See below in the detailed.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

  For a long time, Auriga's stick figure was made up of a 5th star, being El Nath; I mentioned this star earlier in the spring as the northern claw of Taurus.  The 5 stars together naturally gave Auriga a lopsided-pentagon shape.  When the International Astronomical Union finally decided to give El Nath to Taurus only (similar to how Pegasus lost a star to Andromeda mentioned a few weeks ago), Auriga was transformed from a pentagon to more of a "diamond" shape, which the labeled stars outline above.*  We will reach a day next month when Capella will be visible for the same number of minutes in the morning and evening.  At our latitude, this was common with aforementioned Deneb early in the year, and other dimmer stars at similar declinations have it seen also this way.  The more north a viewer is, as the grid reminds us, the more stars we see as near--or completely--circumpolar above the horizon.  With Capella, it is seen circumpolar with an unobstructed horizon when viewed at the wester U.S./Canadian border: 49º.  As a fun sighting, I have seen the star at 50º in southern Alberta; the atmospheric pollution gives Capella a red appearance when seen at its lowest in altitude.  With enough pollution, the attractive red-green, Christmas-like twinkle is not yet visible.  At 38º N., we see Capella this way in the northeast evening sky starting in late October-early November, depending on which hour we look.

*The Starry Night Software which I use daily, maintained the pentagon shape however, for--I am guessing--to show the original shape; hence my not including the stick figure. 

Perseus: stick figure and illustration

Event Date: May 26th
Time: 5:00 AM

Brief

   Our morning northeastern sky showing continues today, highlighting another constellation: Perseus.  Translated to 'the hero', he saved Andromeda from Cetus the Sea Monster.  Refer back to this link that I included last month, regarding the myth including these two.  Perseus rising with some stars labeled.  The clock is forwarded 30 minutes later from yesterday's time to show the entire stick figure above the horizion.  By the end of the season, it will be higher in the northeastern sky to see.  Perseus' most popular star is Algol, which is an eclipsing variable.

Detailed
  
   Algol's companion star faithfully transits it every 2 days, 20 hours and 45 minutes, dimming it from 2.1 to 3.4 in apparent magnitude.  More detail about the dimming can be found here:
Besides Perseus and stars, I kept the stick figure of Aries to the right (south), and star Capella to the bottom-left (east).  The star is to mark the evil (or 'ghostly') eye of Medusa, which as the myth states, Perseus is holding in his hand,  As the classical illustration shows overlapping the stick figure here, the head of Medusa is shown near Rho Persei (Gorgonea Tertia).
  Capella, stated above, rises shortly after most of Perseus' more visible stars, and is much brighter than any of them.  I will show more of Capella as it gets higher and easier to see this summer during the morning; it is the brightest star of Auriga the Charioteer.  The star is far enough north that as the Sun sets this month, Capella sets at about the same time.  I will show that tomorrow.  For now, sticking with Perseus, here is a magnification to more clearly show him holding his sword in his right hand, and Medusa's head in what appears to be a sack (is that term still used?) of some type.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Aries and visible stars

Event Date: May 25th
Time: 4:30 AM

Brief

   Aries is not a bright constellation, and only has two stars which are easy enough to see: Hamal  (magnitude 2.0) and Sheratan (2.6).  They are two very different stars: although similar in distance, Hamal at 66 light years away is an orange giant, much cooler than 60 light year-distant Spica; the latter has a luminosity of 22 Suns

Detailed

   Both stars are shown rising in the east-northeast during the first stages of twilight this week shown here:

As we move into June next week, the early Sunrises will continue to keep them from showing for long, and a clear horizon will be needed.  During summertime, they are easy to see higher up, although with a single glance, they do not draw much attention from viewers.  Instead, they are more focused on the return of the Pleiades Star Cluster, which I have mentioned a couple times already when it was setting earlier in the season.  The great Square of Pegasus is the other asterism that dwarf Aries' stars, since the rest of the constellation's starts are either moderately dim or very dim.  There is one close to Sheratan named Mesarthim (3.8).  Along with Sheratan and Hamal, the Ram's head is formed, which is shown with image two and also including the almost-equally dim 41 Arietis at the other end of the stick figure.  While these dimmer stars are visible in a dark enough sky, they are more difficult with a light-polluted sky.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

   The rest of its body, in a sitting/resting position, is many stars too dim to see easily.  Even if they were easy enough to see, they do not outline a ram's figure the way that stars of Leo and Taurus do, as examples for their respective animals of a lion and bull.  I haven't talked too much about Taurus aside from the Pleiades which is thought of as a brand on his back.  As he gets out of the glare of the Sun this summer, I will revisit him as a topic.

Jupiter soon visible in the morning

Event Date: May 24th
Time: 5:45 AM

Brief

   Although Jupiter is still too far in the Sun's glare to see, while also being a couple degrees south of our star, it is gradually seen to emerge a little more each day.  Our revolving around the Sun makes it seem as if it is moving against the stars faster than Jupiter west to east.  Jupiter is at about its fastest rate in pro-grade motion, which also leads to it emerging from the Sun more slowly than further Saturn, Uranus and Neptune.

Detailed

   Jupiter and the Sun are now in the constellation of Taurus, meaning that they are almost as north as we see them on the celestial dome: Jupiter is almost 21º north, being a little over 2 1/2º of it's 23.5º at the solstice.  At more than 18º, Jupiter is the furthest north that we have seen it since in Cancer about 9 years ago.  Jupiter is still moving north each day, and will continue to until retrograde begins in early fall.  By then, it will be close to as north as the Sun at the solstice.  With the Sun having retreated to the celestial equator, why does that matter?  Not only will we have more hours of darkness to see Jupiter then; it will spend more time above the horizon, with an impressive opposition high in the sky.  This year through 2015 will be the best to see Jupiter high at opposition from our location.  At latitudes not further south, such as those for Hawaii, Mexico, India and the far-east islands, Jupiter will be seen at or near zenith, exact latitude depending and which month it is viewed.
   The image includes the ecliptic and celestial equator along with the celestial grid to remind us of the declination of both solar system bodies.  As they rise, they curve from the horizon, and set that way also.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Venus nearing conjunction

Event Date: May 23rd
Time: 8:15 PM

Brief

 The Sun continues setting a little less than a minutes later each day this week.  As we approach the summer solstice four weeks from now, the number of seconds between sets will continue do decrease.  The Sun is about 20 minutes shy of its latest set time, happening in late June.  Between now and then, we will lose Venus, as it reaches conjunction in early June.  Here is the planet zoomed out, shown in orbit with the celestial guidelines and the waxing crescent Moon at about 3 days old.

Detailed

   Its retrograde motion, coupled with twilight time lengthening by the week, will make Venus too hard to find very soon.  It has waned to a 6% crescent and continues to catch up with us in orbit.  Therefore, with a 53 arc-second diameter (26.2" radius), our formula for area gives us only 129 area arc-seconds to see, compared to a little over 300 back on April 30th when Venus reached greatest brilliancy.  The result is a loss in apparent magnitude, although the glare of the Sun interferes with seeing Venus more than the lost area lit to our eyes.
   As for the Moon mentioned for the image, I also included its orbit to show that despite being high in the sky at transit today, it will lose ecliptic latitude and declination this week, transiting a little lower each day.  Look at the top left of the image to show how much it the orbit merges with the celestial equator, and refer back to my precession of the node entries for reminders on why I bring this up.
   The second image jumps back to Venus.  This will be the last week before [inferior] conjunction that I show Venus zoomed in, as it has waned considerably and getting close to the Sun.  With the increase in angular size to almost 1 arc-minute, that is slightly larger than Jupiter at opposition.  I will use magnification 200, to help see the lit portion a little better.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Saturn and Mars: same altitude

Event Date: May 22nd
Time: 10:26(.13) PM

Brief

   This week, Mars continues to dim to the magnitude of Saturn.  Both are about the same now at +0.4, with Mars "just a hair" brighter (for lack of a better phrase).  While this similarity goes on, we can also see them at the same altitude, a few minutes earlier each evening for the next several weeks.  Mars eventually catches up with Saturn this summer, as it revolves around the Sun about 20 times the frequency of Saturn.  They are of course two very different planets, as I have described over these last two months: Mars has a rust-covered surface and a very featured surface overall, and Saturn is a gas planet many times larger with rings made up of billions of icy particles of various sizes.
  

Detailed

  Look at the image with the altitude/azimuth grid included.  I picked a spot on the horizon that if a telescope is placed at that azimuth (208º) the slew measurement to each planet is almost exact. They are 45º 28' high, just slightly past the sky's halfway point between the horizon and zenith. 

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

This altitude will change slightly each day, as both planets move against the stars.  Saturn is still in retrograde while  Mars is picking up speed in prograde gradually, and soon to move from Leo to Virgo.  Early last month, I showed Mars' celestial path and how it was close to the Virgo border briefly before its first stationary marking.  This time, instead of turning around, it will move through Virgo a little faster each day, eventually going through the other zodiacal constellations at a faster rate until about the time of conjunction with the Sun.  As the year moves on, Mars eventually reaches the part of the sky where the Sun is in the late fall and early winter, seen much lower in the sky,  It will also be much dimmer than it is now, and especially when compared to its opposition in March.  As we move further from Mars in our smaller orbit, we eventually see it looking not much different than a +1 magnitude star, with alot of its color not visible to the eye.

More on Hercules and M13

Event Date: May 21st
Time: 12:00 AM

Brief

   Yesterday while showing Hercules and its Keystone asterism, I asked readers if they could identify a bright star not far east in the sky, from the constellation.  That star, which I have shown with two others forming another large asterism, is Vega-- forming one third of the Summer Triangle.  If we forward the clock ahead two hours from yesterday, taking us into the next day, all three stars of the Triangle clear the horizon as seen from our latitude.  I will include the Triangle figure in the image below, yet keeping Hercules and yesterday's feature as well labeled: the Hercules [star] cluster. 

How is Vega important in relation to the cluster?  Along with the star Pi Herculis (spelling changed to indicate that it is a star within the constellation), Vega forms a line that takes a viewer almost straight to the cluster.  Look at the zoom-in below, which gives a wide field of 30º.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   I didn't give stats about M13 yesterday, so will here.  Some are similar to M3, which is the globular cluster that I displayed earlier in the season.  M13 is listed as the exact same magnitude as M3, and about 12,000 light years closer.  As a result of this, M13 is listed as the more "spectacular" of the two, if using the same size telescope especially.  Some feel that M13 has more of a 3-D feel, and more "sparkly" or "snow-flakey".  Use whatever words you like, and personally, I like both.  Coincidentally, both are about the same latitude in the sky, putting them close to zenith at and near transit: M3 is at 28º, while M13 is 36º.  Despite the 8º difference, when transiting, they both appear very high up.  Just about every telescope used require a diagonal to attach to the eyepiece when this high, so viewers can view while directing their heads parallel to the ground.  It is much better this way than perpendicular; this gets a little hard on the neck after a very short while!

Hercules and its star cluster

Event Date: May 20th
Time: 10:00 PM

Brief

Rising in the east-northeast during mid-spring weeks is a dim constellation, with a very attractive telescope target within its boundaries.  Hercules, the 'strong man' is made up of stars that require a dark sky to see easily.  It contains an asterism which makes up his torso, called the Keystone.  It is a quadrilateral with a lopsided-trapezoid appearance, containing three 3rd magnitude stars and one in the high-2 range.  Here is a zoom-out of the cluster with the keystone emphasized slightly and labeled.  What's that brighter star just east (bottom left) of Hercules?  I have mentioned it for several morning and late night entries, and will come back to it tomorrow.  If you have followed the sky closely over the last two months of my doing this blog, perhaps you already know however.

Detailed

  More importantly, between two of the stars in the keystone is a globular cluster.  Even in small telescopes of 4 or 5 inches, a dark sky and the right magnification helps gives this cluster a good appearance.  An 8 or 10" scope is recommended, although larger apertures are strongly recommended to see stars near the core more clearly.  The field of view used for this second image is a 38 arc-minutes, translating to a magnification of about 80x.  Normally I view the cluster with less magnification when this low in the sky, to help contrast, although with my 8" telescope, this works well when it gets high at transit time; that happens during the wee hours of the morning this month.
The final image (yep, 3 today!)  have us zoom out again, to show where the cluster is seen within the keystone.  That zoom is only about 5 or 6x, which is more binocular-ish.  That final showing includes the entire keystone in the field, and the cluster looking more smudge-like.  Even that small, which is the way it may also appear in some telescope's finder-scopes, it can be interesting to look at.  After all, when Messier (M13 for those keeping track of where this one falls in his catalog), was noticing these non-comet celestial wonders, he may have used telescopes that only magnified it that much!

 

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

  

North celestial pole and stars

Event Date: May 19th
Time: 10:00 PM

Brief

   This evening, I will move from planets, asterisms, and everything else easily visible...except for Polaris!  I have mentioned briefly in past entries that this star is easiest to see very close to the north celestial pole, hence its popular "north star" dubbing.  While we often see this star with the eye all alone in a very small part of the sky as Ursa Minor [Little Bear's] tail, serious astronomers who do polar alignments with their telescopes get to know the surrounding star field.   After so long, they (we) get to know it well enough over time, that they don't even need to refer to star fields in books, software or online.  Here it is, within both a 2º field and a 1.4º one.  The latter marked in light blue, marks precisely how far Polaris is from the north celestial pole" 41 arc-minutes. 

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   Why have I labeled other stars in the image?  They are all the next-"brightest" in apparent magnitude after Polaris, although hundreds of times dimmer!  The brightest labeled is in the high-8th magnitude range, while the others are low to mid-9th magnitude.  The 10th and 11th magnitude ones can still be seen in telescopes as small as 4", although a 6" or larger is recommended.  The 8th and 9th are more helpful to center on the pole, being brighter.
  Since Polaris spends the rest of the century, literally, approaching the north celestial pole as a result of axis precession its own proper motion, a slightly smaller field will eventually be needed to center telescopes at the axis.  For now, the 2º is worthwhile using, marked in the different blue-shade.  This way, other star patterns within the field may be helpful in aligning a telescope to the axis.  The main reason for this alignment as a reminder--especially with equatorial telescopes--is improved tracking of the telescope in right ascension.  However, alt/az telescopes lined up to the pole can also track better if motor-driven, as a special function on them is used to map out the sky.

'Winter Circle' stars setting

Event Date: May 18th
Time: 8:45 PM

Brief

   I have come back to the Winter Circle a couple of times since its peak evening positioning during the namesake season.  Now that we are in the second half of spring, a little over a month before the summer solstice, we see the constellations and stars of the Circle setting either before or after nightfall.    Although they are just becoming visible in the glare of the Sun, with some requiring binoculars until about 15-30 minutes later, we see some of the stars still high enough in [altitude].

Detailed

   Look at the celestial grid and equator included in the image, to remind us of the different declinations of each star still high enough to see: Sirius is the furthest south, so it is just barely above the horizon and hardly visible despite being very bright.  Rigel, being south and further west of some of the others, is already set.  When navigators first saw these 1st magnitude stars appear in the winter and spring evening skies, it further defined the nautical period of twilight.  The time for the image marks the beginning of this twilight period, which varies in length with the seasons and the Sun's position to the horizon once set.  The same goes for civil and astronomical twilight, and I will talk about those in a little more detail next month.
  Among the stars is Venus, which outshines all of them by dozens of times.  At 2º from star El Nath, which I introduced about a week ago, the planet will move among the Winter Circle stars as it picks up retrograde rate and quickly plunges towards the Sun's glare over the next two weeks, eventually disappearing from sight and waning to a very thin crescent right before inferior conjunction. 

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Saturn transit and Moons

Event Date: May 18th
Time: 10:51(.51) PM

Brief

   The time above is that of Saturn's transit, which is happening about four minutes earlier each evening.  Since its opposition last month, Saturn has improved in altitude daily once visible during twilight.  With the Sun setting past 8 PM now, and twilight lingering longer, it means that it Saturn is not seen with the eye alone until about 30-40 minutes later, depending on one's latitude.  It remains high enough in our sky to view until just before dawn,  The two hours before and after transit--above the atmospheric pollution--let us see the divisions between the rings most easily.  When skies are stable however with little or no wind, we can also still see enough of the disc of Saturn.
This first image shows it at transit.

Detailed

  At a little more than 6º south of the celestial equator, Saturn will be seen lower towards the horizon at transit for the next 5 years.  Once it reaches the position against the stars that our Sun is at the winter solstice, it transits at similar low altitudes for about a year.  For the next 7 years after that, it gradually transits higher, eventually reaching the celestial equator.  Southern hemisphere observers are having the fun of seeing it higher in the sky now than we are, and further out of atmospheric pollution for viewing.  For locations near the equator, they see Saturn high in the sky throughout its revolution.  Of course, with the amount of humidity at those latitudes, a clear image Saturn for viewing may not come out as well as it would at mid-northern/southern latitudes.
   The following zoom-in shows the Moons' positions around Saturn, with a field of view of 12'; this gives a magnification of about 350x.  With stable skies and Saturn near or transit, Saturn should look very good with this magnification.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Mars' "loop" in Leo

Event Date: May 17th
Time: 8:11(.08) PM

Brief

   Mars has spent alot of time in Leo the Lion over the last several months.  Since early December, it has "looped" south of the constellation's brighter stars, which make up the stick figure shown in the image.  Using the 10-day increment markers, the celestial path below shows it moving west to east (prograde right to left) against the stars, left to right in retrograde, and finally prograde again.  Even before the start of this path, Mars had still spent a few extra weeks in Leo, south of the Sickle, which I talked about in March.
Below we see Mars at transit, which the time above reflects.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

   While the loop is impressive, look at one other characteristic of it: the angle.  I left out the ecliptic intentionally, which is a hint to what the Mars has been doing over the last 5 1/2-6 months.  While in prograde in Leo, it started to head south; retrograde brought it more north, and resuming prograde is taking it south again.  The ecliptic latitude is different for both prograde stints, which reflects our perspective of Mars versus the plane of our Sun's path.  The angle itself reminds us that this is the part of the sky where the Sun is going through in late August and early September, when daytime starts to shrink more quickly and dark hours increase.  If we were to extend the path, we would find Mars quickly moving south for the remainder of the spring and throughout summer; it will go through the part of the sky where the Sun does in the autumn and winter for our hemisphere.  I will show this path again next month when it is still spending its last weeks in Leo, and again in July as it starts to catch up with Saturn in Virgo.  Correct-- another visible planetary conjunction isn't far away, although the planets will not be anywhere near as bright as Venus and Jupiter during their Mars Jupiter conjunction.

Galactic center at transit

Event Date: May 15th
Time: 3:20(.58) AM


Brief


As seen from our longitude, the galactic center transits at the time above.  Yesterday, I showed a part of the sky where the anti-center of the galaxy is.  The star El Nath in Taurus is the closest easy-visible star to the 180º mark for the galactic equator (opposite center).  Early this morning, we turn our attention back to the center.  Under dark enough skies, the Milky Way is seen at its "richest", most visible.  I included in purple, the galactic equator and meridian, showing exactly where the center is, as well as the ecliptic and general [transit] meridian.  The latter is shown to indicate the transit of the center, when we see it at highest altitude. 

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

   Here is what is neat to remember: at our near 38ºN, the center transits at altitude 24.3º, being at declination -27.8º.  Our Sun on the winter solstice, which I will further talk about in December when it happens, reaches declination 23.5º, which as a reminder, is the same as the Earth's axis tilt.  Since the Sun never gets as far south as our galactic center, there is no way that will become lined up with the center, where a black hole dominates; light cannot even escape that hole, hence its name.
   The Mayan calendar ends this year, when the Sun lines up with the galactic meridian.  Looking at the ecliptic in green, the intersection of it with the galactic meridian marks that spot.  What many people do not understand, as a result of those fearing "astronomy doomsday" and creating of paranoia in the media, is that the Sun meets this intersection every year.  It will be 6º from the galactic center, therefore out of line with the black hole, and the Earth will not get "sucked into" the hole.  Even if it did cross the celestial coordinates of the center, it still perhaps would not have a gravitational pull, as the black hole is thousands of light years away, or 6 trillion miles times thousands.  Far enough for you?  In a word, relax...and if you really want to celebrate the evening of December 21st, do so for the beginning of winter and the holidays; not a made-up (astronomical) doomsday.

Venus begins retrograde motion

Event Date: May 16th
Time: 8:00 PM

Brief

   Despite showing a local path in recent weeks for Venus, I have not shown a celestial path for quite some time; this is a good time for that, as Venus has started its retrograde motion.  This also means that separation between Venus and the Sun will quickly shrink, after being as much as 46º at greatest elongation back in March.  Notice the path here, and the 10-day increment markers.  The image is zoomed in 2x, to show the start of retrograde a little better.  As it continues, the markers will separate again, for if I remember to show the plot again in early June.  For now, the markers become closer together, as Venus reaches stationary.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   While still separated enough to see easily in the evening, daytime viewing of Venus will come to a fast end for a couple of months-- even when using an observatory.  After Venus retrogrades faster past inferior conjunction in June and comes out of the Sun's glare, we will beable to resume daytime viewing by mid-summer.  By that time, it will be separated enough to not only see easily; there will be less of a risk of accidentally sweeping the Sun with a telescope!
   When we see outer planets start retrograde, it means that we are catching up with that planet in our orbit; opposition isn't far away as well.  With Venus and Mercury as inner planets, it is the same, except they are catching up with Earth.  If a viewer was able to go to either planet and view Earth, opposition would happen at--or close to--the time that the planets are at inferior conjunction from our perspective: the Sun on one side of them, and the Earth 180º away.  Since the days on both inner planets are so many Earth-days, it means that a "fantasy" visitor would see Earth become a little brighter over a long span of time; during "night" on each inner planet.  Mercury rotates once every 59 Earth days, so it's night at the equator would be about one Earth-month.  Venus rotates even slower, at over 243 days (longer than its revolution!), so a night would be about four Earth-months.  If you ever want to experience this as a witness, get ahold of software such as the one I use here for imaging; most brands allow travel to other planets to view Earth.

Venus, El Nath and "anti-galactic"

Event Date: May 14th
Time: 9:00 PM

Brief

    As Venus sets in the west northwest, still at an outstanding declination of 27º (almost 4º better than the Sun at the time of the summer solstice about 28 minutes further east), it is spending a few minutes close by a popular star: El Nath.  The reason of the star's popularity isn't because it's visibility as Taurus the Bull's northern horn tip however: it is the star that marks the anti-center of our Milky Way Galaxy.  To show this, I am including the galactic equator, which marks our Milky Way as we see it under dark conditions.  I am also marking the perpendicular galactic meridian. 


Detailed

    Although Venus is seen near the Meridian and will cross it in a few days, that is not why I am including it.  Instead, observe the intersection of it and the equator.  On the other side of our sky, 180º away along both of these guidelines close to the Sagittarius/Scorpious border, that is a precise part of the sky where the Mayans predicted that the Sun will be on what has been translated as "doomsday".  Of course, it is the day that their calendar ends and there will be no doomsday associated with astronomy.  Why?  I will mention that tomorrow, as that part of the sky is now seen in the wee hours of the morning.  For now, here is a showing of Venus and eastern Taurus with the two guidelines.  The other (southern) horn, Zeta Tauri, is labeled as well.

   The second image shows Venus near El Nath in a 5º field, which will be the case for the next few days as Venus reaches stationary and go retrograde tomorrow.  As the case with other planets, Venus will pick up in retrograde as we see it against the stars, yet will start slowly enough that we see it near the star in binoculars easily.  This evening, the separation is 1.8º

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Jupiter emerging; Mercury low

Event Date: May 13th
Time: 5:45 AM

brief

I have two positives to mention and one...not something else, not so much so.

Good #1: Mercury continues to slowly brighten and now is an impressive -0.7.  Although low towards the horizon before Sunrise, the planet may still be possible to pick up with optical aid through atmospheric pollution.
Good #2:  Mercury and Jupiter will have a very close conjunction coming up over the next few days when Mercury is -1.6 in magnitude and Jupiter is a little brighter at -2.0.
Now, what is the bummer, you ask?  If you have followed my entries for the last two weeks or--even better--for longer, you may recall that Jupiter was approaching conjunction for several weeks, and just barely hovering over the Sun barely visible at the end of April.  As for Mercury, it has been approaching inferior conjunction for a few weeks now.  Therefore, forget about good #2, making my mentioning it sortof worthless (sorry!) as the conjunction will not be visible to us from Earth; both planets will be deep in the glare of the Sun.

detailed

   With the above mentioned, silliness aside, you may wondering why did I bother waste time mentioning good #2?  Simple: even if we cannot see a planetary conjunction, it is good to (1) acknowledge them as a result of very close ones being rare; (2) it helps astronomers worldwide to remember to stay up to date with planet positions as they revolve around the Sun.  The next time that there is a either a very close conjunction of two planets, or less-close ones of two bright planets such as Venus and Jupiter at 3º back on March 13th.
   Finally, for those wondering when we will see Jupiter easily again, after the Mercury conjunction, it will not be long: try looking low in the east-northeast in early June.  Despite lots of glare from the early-rising Sun, bright Jupiter may be barely visible to the eye alone by these first weeks of summer.  Jupiter will be easily visible as a very good morning target as the Sun eventually moves just south of it a few weeks later.
   For today's date, I will label the two planets, with Jupiter deep in the Sun's glare behind it.  For the next few weeks, watch the separation of Jupiter from the Sun, as Jupiter rises a little more than 3 minutes earlier each day, still moving quickly in pro-grade motion, in the constellation of Taurus the Bull.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

More on M3 & neighboring stars

Event Date: May 12th
Time: 12:20(.41) AM/8:00 PM

Brief

I briefly mentioned Canis Venatici yesterday, as the "parent" constellation of large globular cluster M3.  (C)or (C)oroli, which I introduced yesterday as well, is nearby M3 at magnitude 2.8.  It is a key star to use along with Arcturus, for easily finding the cluster.  At 13.8ª away, while we imagine a line straight from CC to Arcturus in Boötes, M3 is almost directly in line, at just short of 12º from Arcturus.  Take a look at this image for when the stars are almost identical in altitude, to see what I mean.  From our latitude, this happens for the two while Arcturus is shortly past transit by 17 minutes, and 38º declination CC is a little more than one and a half hour past transit.

Detailed

The way wee see the three celestial bodies above is the way they are at this hour for our location.  However. if our latitude was different, especially in the southern hemisphere, we may see them in line only very low to the horizon while rising instead of setting at some latitudes.  Remember that all bodies rotate around the north or south axis, as opposed to east and west azimuth coordinates at the horizon.  As an example, sticking to our horizon, lets forward from just after midnight to early this evening, when the three are rising.  Look at the altitude difference: declination stays fixed (disregarding precession and proper motion for the stars) which has us see the bodies at different configurations with each other.  The stars are more similar in azimuth below than they are in altitude, seen below!

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

  

[Globular cluster] M3 at transit

Event Date: May 11th
Time: 11:29(.45) PM

Brief

   Springtime is the best season to view the globular cluster M3, which transits high in the sky and near one of our brightest stars in apparent magnitude.  With the zoomed-out image shown here first, we see the location of the cluster, at 28º north and therefore at our latitude, seen at 80º in altitude.  It is the first deep sky object discovered by Messier, while the first two that he categorized (a nebula and another cluster in Taurus and Aquarius respectively) were discovered by others earlier.  I will talk more about those in upcoming months, when they become visible during the summer mornings.
Looking in the same part of the sky at M3 is Arcturus, which is the recommended star to find the general area of where the cluster is.  The other star I labeled forms a nearly-straight line with Arcturus and M3.  That star, is given the Latin name Cor Caroli (Charles' Heart).  It is the brightest star of the constellation Canes Venatici: the Hunting Dogs.  Not to be confused with Orion's two dogs, Canis Major and Canis Minor, Canes Venatici (with the spelling of the first word slightly different) is two dogs within one constellation, albeit a very dim one.

Detailed

   
   The second image here shows the cluster zoomed in with a field of 1º.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Although this doesn't help magnify the core too well, it does help fit the 48 arc-minute cluster into the field completely.  As I have mentioned before when magnifying, it is best to not let contrast degrade.  Therefore, magnifying too much not only shrinks the field and cuts off stars, but makes the core seem dimmer.  If you want to still magnify enough to see the core of the cluster, limit it to a field between the "ballpark" of 0.7 and 0.8º at most; this will still give a good enough magnification range of roughly 90-100x for most eyepieces.  When skies are clear and dark, as they hopefully are with the Moon out of the way at this hour, the cluster can be seen at its best.  It is also good to not have moisture in the air, with humidity low.
   I mentioned during my Pleiades talk awhile back, that open clusters are loosely bound by gravity; globulars such as M3 are tightly bound.  At 35,000 light years away and magnitude 7, that can indicate how many stars this globular has: about half a million.  Find out more stats about the cluster with this link:
http://messier.seds.org/m/m003.html

it is a huge gathering of stars, to say the least!

Summer Triangle up at Midnight

Date: May 10th
Time: 12:00 AM/5:36(.22) AM--see detailed

Brief

   At the end of yesterday's entry as a slight teaser, I brought up the topic of a high-in-the-sky asterism; one which is easily seen for half of mid-spring nights, starting at about midnight.  That same figure is even more visible during the summer months.  Naturally, I am talking about the Summer Triangle...yes, again!  As we are now only about 6 weeks from the star of Summer, the triangle's stars are visible not long after dark, with Vega and Deneb already high above the horizon before 10 PM.  Altair, not being as far north, rises last this evening at 11:15 PM for our location. 
   The 1st image shows the triangle looking east-northeast, as we begin a new day on the calendar.

Detailed

Although the Triangle is seen at its highest around this hour during most weeks of the summer, we can still see it as high just before the Sun's light washes them out; image 2 shows that, with Vega and Deneb not far from our zenith-- our highest point in the sky, or the equivalent of 90º altitude.  If you remember my including the alt/az grid in past entries, I usually showed the horizon at 0º.  This time, as well as the zenith marker, I will include the meridian and alt/az grid, since I am showing the Triangle at transit time for its center position.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

   For latitudes between 20 and 50º north, seeing the triangle at transit requires either lying on the ground (to avoid a stiff neck later!), or just looking straight up from a standing position.  With most altitude and azimuth telescopes, this can be a little challenging with an eyepiece alone.  Therefore, be sure to carry a diagonal with you, which puts the eyepiece parallel with the ground and easier for viewing comfort that way.  The more north a viewer is, the lower the triangle transits.  Of course if too far north, it never gets dark enough during some months to see it. 

Spring Arc pre-dawn setting

Date: May 9th
Time: 4:00 AM

Brief

   Back in February and March not long after dark, we saw the Spring Arc stars rising in the eastern half of the sky.  Now, a couple months later and not long before dawn, those stars of the Big Dipper, Arcturus and Virgo are still above the horizon, yet in the west and getting lower.  As seen from our latitude and other mid-northern ones, Spica is first to set first, even though it is the last to rise, after the Dipper handle stars and Arcturus.

Detailed

Looking at the celestial grid in the image, it reminds us why Spica is the last to rise and first to set: it is the furthest south of the stars. 

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

   As seen from the mid-southern latitudes, it would be the first to rise and last to set, while the Big Dipper would spend alot less time above the horizon.  Arcturus, at 19º north, is best viewed from that hemisphere, but can still be viewed easily at southern latitudes near the equator.  For how long southern viewers see this bright orange star, depends on what evening of the year they start viewing.  When seeing Arcturus when it is at opposition, rising at Sunset in the spring, it is up all night long; this is the same as planets being at opposition, although the stars are fixed.  If a viewer there--or even from the northern hemisphere--starts viewing Arcturus when it is in the west at Sundown, it will only be seen for a small amount of time.  Time Arcturus and the other spring arc stars daily, as they are seen in the same part of the sky about four minutes earlier each day. 
What other asterisms do you see during the night?  Tomorrow, I will remind of one very popular one, which is now rising very shortly after dark, and high in the sky for the entire night after that!