Venus at 20% crescent phase

Event Date: May 8th
Time: 8:06(.12) PM

Brief

  Venus continues to wane as a crescent shape, although it also becomes larger in angular size.  It is still very bright, and setting a little over three hours after the Sun.  This gap in Sunset will change more rapidly as Venus approaches us in orbit.  Not long before that, we will see it in retrograde, with its separation from the Sun quickly decreasing.
   The first image is a zoom-out, as a reminder of its current position with the Sun.  It is 33º in altitude at the time that the Sun sets, and currently still far enough separated from the Sun to see with the eye alone in the daytime; that gets more and more challenging as we get towards the end of the month.

Detailed

   The second image is a 1/4º field of view, showing Venus.  Using the area formula that we have in past weeks, it has dropped slightly below the 300 arc-second mark which it achieved at greatest brilliancy.  At 21 arc-seconds in radius and 20% illuminated, that calculates to 290.2 for [arc-second] area. 

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

Venus' visible area will continue to drop as it continues to wane.  As it does, so will the apparent magnitude.  Because Venus is approaching us quickly, the brightness only changes by a small amount.  By the time that such is noticeable, the planet is already lost in the glare of the Sun, and too hard to see anyway. 
   Besides remembering to never look directly at the Sun, make sure not too look towards the Sun's position, within what is about 20º to either side; its surrounding glare alone can be hard on the eye.  Viewing from inside an observatory dome with the roof turned properly, is best, for blocking out enough Sun.

Uranus and [star] 44 Piscium rise

Event Date: May 7th
Time: 5:30 AM

Brief

We have a slightly brighter target this morning to feature, in comparison to Neptune: Uranus is coming back into view!  Although we will not easily see it this month, it is visible enough through binoculars to see low towards the horizon.  Whereas Neptune easily gets lost in atmospheric pollution at nearly-8th magnitude, Uranus is better than 6th magnitude, albeit slightly. 
Here is a zoom-out with the labeling of the 7th planet from the Sun, about 1.8 billion miles away from us.  It is 12º in altitude at the time shown, although can be seen longer through a strong enough telescope until about Sunrise time.

Detailed

By early June, despite the long morning twilight time, we will have a much better view of Uranus, and may even beable to see a little of the green-blue color of the planet from its methane makeup.  Find out more about Uranus' gaseous combination here, noticing that the small percentage of methane gives the most interesting color in my opinion.  The second image shows this color, although it will be fainter when seen in real life at low altitude through small telescopes.  A we see Uranus closer to transit later this year while still dark enough, further out of atmospheric pollution, the color will be seen better.  Try a 6" telescope at minimum, although an 8 or 10" is ideal.  Remember to also keep magnification less than a small telescope's recommended maximum when looking for color, as stronger magnifications can lead to contrast becoming worse; the result of this is less of the blue-green color.  Interestingly, at an identical magnification, the star 44 Piscium is seem only 0,1º from the planet.  A couple of days ago, the two were at their closest in separation, at less than 3 arc-minutes.  As Uranus moves west to east against the stars in pro-grade motion, we can notice the star and Uranus separate further.
The field of view is 1/2º, which easily fits the close pair.

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

Neptune before twilight

Event Date: May 6th
Time: 4:25(.42) AM

Brief

For at least one day during both March and April, I mentioned the loss of Neptune into the glare of the Sun.  Now, as the solar system's most distant "classical" planet is rising about four minutes earlier each day (and the Sun only rising about 1 minute earlier each day), it has given Neptune a chance to be visible for a short time in western Aquarius; it rises about three hours before the Sun, meaning that for a little over an hour, it is visible in complete darkness and high enough out of atmospheric pollution to view.  Here is Neptune well placed while the sky is still at its darkest; that being, just prior to the start of astronomical twilight. This first image shows that, with the ecliptic and celestial equator included.  By putting them in, we see that the Sun is still far enough south to be affected by twilight early.

Detailed

Starting at about 4:30, our location on Earth is rotated enough towards the Sun, that it starts to slowly wash out the darkness of the sky.  An hour later, Neptune can only be seen through powerful-enough telescopes, with the Sun getting closer to the horizon.  As mentioned in the brief, astronomical twilight begins about 4:30 AM at this location, meaning that the Sun passes the 18º mark below the horizon.  If you remember the celestial grid that I have often shown for planets and stars so far, it can be used for the Sun sub-horizon just as well as it can above the horizon.  Astronomical twilight at this time of year lasts for a little over half an hour, until the Sun is 12º below the horizon.  By this time, it is still almost too dark to see in a location with no other lighting, although the sky starts to reflect just enough blue light back to Earth for us to barely see.  Then, nautical twilight begins, which is when we lose Neptune fast in binoculars and most small telescopes.  This lasts until the Sun is 6º below the horizon,  For the final "climb" of the Sun, only the brightest stars with an elongation large enough may be seen.  As for us, it is light enough to walk around and do some activities.
   As Neptune continues to rise a little earlier, and the Sun finally starts to rise later by Summer, we will see Neptune higher in the sky before Sunrise, and eventually far enough north of it by late fall that as an evening-viewed planet, it will be seen for hours.
   This second image is good as reference for when Neptune is high enough above the horizon, with a 1º field of view.  Although Aquarius' brighter stars are dim compared to the average apparent magnitude of other constellations', they can still be used to find Neptune.  Remember that I talked about "star hopping"?  By looking for patterns among stars, even if they are dim, they can help find dim Neptune, which doesn't look much bigger than a star in even medium-size 'scope.  Look for triangle configurations, for example, with a near-equilateral one near Neptune as shown below, or the isosceles one near the top-left. The bigger the field of course, the more shapes can be seen, leading to more of a hopping project.

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

Mercury's improving apparition--somewhat!

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

Brief

   Feliz Cinco de Mayo! 
As for astronomy, let's take another look at Mercury low in the east, as it starts to catch up with the Sun in celestial longitude.  The result of this, means that the declination difference between the two will decrease.  At greatest elongation, Mercury had fallen far enough south of the Sun, that it was rising only a short time before the Sun.  With the spring Sun's glare lasting longer in the morning it was nearly impossible to see Mercury without optical aid.  This first image shows a zoom-out of Mercury in orbit, along with celestial guidelines.  During May and November, we are looking almost directly towards the plane of the orbit, hence no "loop" appearance.

Add caption

Detailed

Now that Mercury is now slowly approaching the Sun again after aphelion and we are seeing a little more lit portion of Mercury, it is starting to brighten.  Between now and just before it becomes hard to see before superior conjunction, it will brighten nicely, with the gap between it and the Sun rising increasing.  The only problem of course, will be that we will be close to the Summer solstice, and trying to catch Mercury while still dark enough will mean trying to look for it between 5:00 and 5:30 AM, depending on one's time zone.  The further south viewers are to the equator, the easier Mercury will be to spot in dark enough-yet-twilight skies.
   This second image is a zoom-in of the planet, showing it waxing as a gibbous, although shrinking in size from our point of view.  At magnitude -0.2, albeit still south of the Sun, try to see it with the eye alone, although being high enough to see above any obstruction would be a must.

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

Saturn, Moon & Spica triangle

Event Date: May 4th
Time: 9:00 PM

Brief

   The Moon is just short of full, reaching that tomorrow.  As we get closer to the summer solstice, this full Moon and the next one in early June will be seen low in the sky.  This of course, is about where we see the Sun in the mid and late fall, so it makes sense.  That is, a full Moon is opposite that of the Sun on our celestial dome.
   As for this evening, Saturn, Spica and the Moon make a near-right triangle: if a line is drawn from Spica to Saturn, it is almost perpendicular to the Moon.  The separation of Saturn and Spica is just a little less than 5º.  Between now and late June, Saturn will continue to slow in retrograde motion and go stationary the night of June 24-25th. Between now and then, Saturn creeps up on Spica by another few arc-minutes.

Detailed

   By showing Saturn become gradually closer with Spica, it is worth showing a zoom-in of its celestial path.  Right now, its retrograde motion is just past its maximum rate, from east to west against the stars.  Between now and the stationary date mentioned in the brief, Saturn will slow down.  In binoculars, the view of it and Spica is attractive.  Although looking close together, Spica is 263 light years away, while Saturn is just a little over a light-hour away: light travels approximately 670 million miles an hour, and Saturn is about 900 million miles away.  Also, while the conditions surrounding Saturn are very cold, being far from the Sun, Spica is one of the hotter stars in our galaxy, at over 20,000º(!)
   This second image shows a 15º view of the Moon with Saturn and Spica.

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

Andromeda and neighboring galaxies

Event Date: May 3rd
Time: 5:00 AM

Brief

  Yesterday, I showed the Andromeda Galaxy enlarged, and there are two much smaller galaxies near it, fitting in the same field.  One of them, (M)essier 32, is a dwarf-companion galaxy of the larger M31, while M110 is a satellite galaxy of M31. 
   Before I go further, I will mention that Charles Messier was a French Astronomer who's numerical catalog of 110 "comet-lookalikes" became one of the best known catalogs in the astronomy world.  Through the much weaker telescopes he had then, in comparison to today's, galaxies, nebulae and star clusters looked less clear.  Although some appeared to look like comets, they never moved against the fixed stars, hence figured to be something else.   The image is similar to yesterday's zoom-in of the Andromeda Galaxy, although this time, I labeled M32 and M110.

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

Detailed

   Shaped as ellipses, these two galaxies are simply given that term.  The Andromeda however, is a spiral galaxy, as our Milky Way galaxy is.  More on the Milky Way tomorrow, as I compare it further with the larger Andromeda.  Getting back to M110 and 32, they have interesting characteristics: 32 us believed to have lost stars to 31, and therefore much smaller.  With today's photography taking pictures of 110 in space, including the Hubble, it is observed to have dust clouds.  As a result, it is also called a dwarf spheroid.

Pegasus, Andromeda and close galaxy

Event Date: May 2nd
Time: 5:00 AM

Brief

   The last time that I showed Pegasus the winged horse, it was not completely clear of the horizon while still dark enough to see all of the stars.  Despite the Sun moving a little more towards Pegasus' rising part of the sky each day, the horse rises about four minutes earlier each day; this has helped make at least the square stars, easier to see with the eye alone.  By early summer, these "body" stars will be well placed, high in the sky before dawn, and rising during early fall evening hours, as our nights start to quickly lengthen again.  If your skies are also very clear, while still dark enough, use a telescope to find a deep-sky favorite: the Andromeda Galaxy, located in the namesake constellation near the "V" shape that I talked about a couple of weeks ago.
This first image shows the location of the galaxy, in relation to stars near (And)romeda's head.  Remember that her head star is that often mistaken for one of Pegasus', although it is no longer his "belly" star.

Detailed

 The second image magnifies two of the labeled stars in the first image, and labels a few more.

Using Apheratz (label obstructed above by the M31 marking) as the head/former belly star mentioned in the brief, a naked-eye viewer can follow that star to Pi And, to Mu And, then almost perpendicular to the Galaxy.  The skies for this hour are still of deep twilight, and even if low towards the horizon, these And stars may still visible to see through atmospheric pollution; if not, try in 2-3 weeks.  The galaxy can be seen in deep twilight with a small telescope, and even with the eye alone if no light pollution.  Through a small-field telescope, such as 1º, the core of the galaxy is the only part easily visible.  If viewed under dark enough conditions, more of the galaxy can be viewed.  With an angular size of more than 4 full Moons tangent to each other, being slightly over 2º, seeing the entire galaxy under a dark sky requires a low f-ratio telescope, such as 4 or 5.  Photos of this galaxy are very impressive, using large-sized fields, being the closest bright galaxy to our own.  This final image shows the galaxy via the software imaging, mainly to show its size and the field required to fit it in effectively-- 3º working well.  There are two other smaller galaxies seen near this one.  What are they?  I will answer that tomorrow.

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

Mid-spring Sunset azimuth

Event Date: May 1st
Time: 7:59(.50) PM

Brief
  
   As we reach May-day, we are almost halfway through the spring season.  Starting at this time of year, the Sun starts to rapidly slow in its declination increase to north.  Between the start of June through the solstice, it only creeps up by another couple of degrees.  Until then, as this month [of May] progresses, we can still look forward to days noticeably growing longer, with the Sun setting about about 5 minutes later each week on average.  I mention the rate of change, after emphasizing the rapid change of increase--and length of daylight--between the March equinox late April, up to today.
   The image shows the celestial and ecliptic grids, celestial equator and ecliptic, with the Sun about to set north of west. 

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

Detailed

As we approach summer, the setting azimuth of the Sun is increasing also: west is 270º, and northwest 315º.  The Sun's official setting azimuth as seen from our latitude is almost in between this evening at 290º.  Keep in mind however, that as further north a viewer moves, the closer to northwest the Sun sets; at furthest northern latitudes, the Sun sets close to the direct north azimuth, if not already circumpolar.  The celestial grid acts as a reminder of this, with the different-sized circles.
   One final thing to notice in the image, is the separation change between the ecliptic and celestial equator: it shrinks to the point of them almost being parallel.  Where the ecliptic longitude 90º mark is, very close to the r.a. 6h mark.  The gridline for the two overlap enough to give a distinguishable yellow color.  I talked about the r.a. and ecliptic longitude notation at the very beginning of this series on March equinox day.  For the June solstice coming up, just think mathematically...does it make sense?

Venus reaches greatest brilliancy

Event Date: April 30th
Time: 7:58(.55) PM

Brief

   After several months of catching up with us in orbit, Venus is not quite there yet.  However, it has come close enough to us that we see the most angular surface area.  As I have mentioned a couple times over the last couple of weeks, this lit-area facing us is known as greatest brilliancy.  Remember that this is not the same as Venus being its best apparent magnitude for this part of the cycle, although we are very close to that as well.  To our eyes, it looks as bright as it will for the remainder of the spring.  Using the area of a circle and factoring in percent illuminated, we have an angular area this evening seen at Sunset, of 306.1.  This number will slowly shrink for the next few days, and then more rapidly.  For every time Venus drops in percentage illuminated, that overrides its slower rate of increase for angular size.
   Image one shows a reminder of Venus' altitude at Sunset, while image two shows a 1/4º field of the planet's waning crescent phase--only 27% illuminated with an angular diameter of 38 arc-seconds.

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

Detailed

   Although still impressive, with Venus being as bright as it is, evening twilight duration increasing is means that we have to wait slightly longer each evening o see Venus with the unaided eye.  By the time that we do, it appears a little lower to the horizon than it did the day before.  This will become much more obvious over the next few weeks, and especially when Venus goes retrograde and seemingly "dives" towards the Sun and its glare.  With that said, this is likely the last best week to view Venus at both (a) its most luminous and (b) high enough up to see long into the evening for a long time.  As Venus continues to increase in northern declination, we have nearly 15 hours of it above the horizon, whether day or night!  The declination peek for Venus happens later this week, and I will show the positioning of it in more depth, at that time.

Summer Triangle: low after midnight

Event Date: April 29th
Time: 12:30 AM

Brief     
   At our global coordinates, we will end April tomorrow with the three Summer Triangle stars above the horizon as the clock reaches midnight.  For this evening, I sped the clock ahead by half an hour, so Altair is a little higher.  Vega rises first at 8:36, and Deneb rises second not long after at 9:45.  Being about 7º north of Vega, Deneb spends more time above the horizon.  Both will be seen high in the sky before and during dawn.  Further south and east, Altair does not rise until just before midnight (yesterday into today), and about 30º further south of Vega.
   Here is the image of all three stars, with the celestial grid showing to remind us of the declination of each star.

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

Detailed

   As the celestial grid shows, Deneb is not far from a circumpolar declination, if viewed from our latitude.  If we were not much further north, at least 45º, Deneb would never be seen setting; it would just barely clear the horizon, and spend a few hours very close to it.  Further north, as seen from locations from the western Canadian provinces, Great Britain, Siberia, etc, Deneb would be more visible above the horizon at its lowest.  The further north a person goes, even Vega eventually becomes circumpolar.  Altair would not be that way however, until someone brave enough reached the most northern latitudes nearest to the north pole.

Winter Circle and Pleiades setting

Event Date: April 28th
Time: 9:00 PM

Brief

   During the winter, I mentioned the season-sake "circle" asterism, which involves 6 constellations in our sky.  They are all labeled in image 1 below, along with Venus and the Moon included.  These two solar system neighbors fit in well, as the labeled stars collected, make up one of the brightest asterisms in the sky; all stars included are first magnitude stars, with Sirius the brightest as seen from Earth.  Capella is also one of the brightest, while the others are all either between 0 and +1, or +1 and +2 in magnitude.  As a consistent reminder, either Pollux or Castor can be included in the circle, yet often, not both as a result of their close separation.

Detailed
 
   Image two shows the Pleaides star cluster, which I have also shown a few times since it has been high enough above the horizon.  The cluster is seen in the first image as well, right of the 'Taurus' label, although magnified 20-fold in the second image to a 5º FOV.  With powerful binoculars, this gives a very nice view.  To see it even more spectacularly, use a low f-ratio telescope (3 or 4), which with some common eyepiece focal lengths, gives fields of 2 1/2 to 3º.

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

Mars' recent celestial path

Event Date: April 27th
Time: 8:00 PM

Brief

As I continue the planet position-to-horizon updates, Mars will come next.  Now that the red planet is moving again in prograde motion, it will start to move and an increasing rate from one zodiacal constellation to the next.  As we move further from Mars in our orbit, this illusion of movement is noticeable.  Here is a plot of the celestial path of Mars since it resumed prograde about two weeks ago.  The increment markers are changed to 1 day instead of my usual 10, to show the increase in spacing.  I also magnified Mars and the path so the markers are not so squeezed.

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

Detailed

 Between now and late winter of next year, Mars will also approach perihelion.  As a result of this, despite dimming to an unattractive "spot" in the sky by late this season, we will see Mars stop dimming a few months before conjunction.  This doesn't mean much for viewing it, although since Mars continues to move faster in prograde, it will remain separated enough from the Sun to beable to view easily.  Eventually, as we have seen with the Sun over the last 6 weeks since I started this blog, the evening twilight time will grow, and eventually the Sun will catch up enough with Mars that we will once again lose it from our sight for about four months.  The next opposition of Mars with the Sun, which happened in early March for this year, will be April 8th, 2014.  Until that time, despite the dimming, try to view Mars high in the sky during twilight time, as the planet still rises a little less than four minutes earlier each day.  As it picks up in prograde, this gap between rise times will shrink a little.  By the time that Mars is moving only a little faster than the Sun west to east against the stars, shortly before conjunction, it will set about the same time every evening, after the Sun.

Mercury low in the morning

Event Date: April 26th

Time: 6:00 AM

Brief

  Here is a Mercury position update.  I mentioned last week that as it begins to separate itself from the Sun, it moves far enough south that it remains engulfed in the Sun's glare for the first two or three weeks.  Whereas southern hemisphere viewers see Mercury as well as they will all year in the morning sky, northern hemisphere viewers need to be close enough to the equator to see it easily before greatest elongation.
   I will show its current position this morning, as it continues to gradually brighten in apparent magnitude.  It is currently +0.1 this morning.

Detailed

   Although just past greatest elongation at 26º that puts Mercury far enough south of the Sun that it is only rising 56 minutes before the Sun.  This may sound like alot, until we remember that at this time of year, morning twilight time has increased dramatically over the last two months--by several minutes.  As a result, as soon as Mercury escapes atmospheric pollution and high enough, the Sun's lighting of the sky washes it out.  Binoculars can help find it easily and of course, a telescope while not too light out.  Mercury has been waxing from small crescent shape to gibbous, having passed dichotomy about a week ago, at 50% lit.  Since Mercury is further away and much smaller than Venus, it requires a high enough magnification to observe the dichotomy.  I will show the planet magnified here, as it makes that "swing around" in its orbit, heading to the Sun's far side and superior conjunction in a few weeks.  As it reaches that, it will start to brighten slightly faster.  At the listed time, Mercury is 6º in altitude.

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

Sun & Jupiter celestial path

Event Date: April 25th
Time: 8:00 PM

Brief
  
   We have enjoyed several months of Jupiter as an evening planet, since seeing it rise during later hours in early fall.  However, it is about time to say goodbye to the "king (sized)" planet, as the Sun has been seen moving faster against the stars than Jupiter.  Since a year on Jupiter is 12 Earth-years rounded up, it means that we see the Sun move about twelve times along the ecliptic plane for every one of Jupiter's.  I will plot the celestial paths of each for the last four months; that is about how long it has been since Jupiter has been increasing in prograde motion. to show more of the Sun's path, I hid the horizon in the image.

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

Detailed

Looking at the image, the increment markers for Jupiter separate as Jupiter picks up in motion west to east, while the Sun's are evenly spaced.  Back in December, where it shows Jupiter's markers squeezed together, about twelve of them fit into the gap between the Sun's.  Therefore, it was then that Jupiter was going at about its average rate against the stars.  Since I only have the markers for every 10 days however, there are not enough showing for Jupiter to indicate the fitting.
   Although Jupiter is moving faster than average against the stars in pro-grade motion shortly before conjunction with the Sun, that allows it to be visible and out of the glare for so long before finally becoming engulfed.  When Jupiter re-emerges from the Sun's glare in the late spring, it takes awhile to see it easily; I will show this in further detail late next month.  When it happens this year, the Sun is about as far north as it gets, being close to the summer solstice.  The planet is bright enough to find with optical aid rising then just before the Sun, although not easily seen with the eye and high enough until early July.  It will not be high enough out of atmospheric pollution to see features until later in July.

Venus: waning, yet more "brilliant"

Event Date: April 24th

Time: 8:00 PM

Brief

   Let's get back to the planets after a break of a few days.  Venus is still the main attraction in the sky as it is about a week away from greatest brilliancy.  Do you remember the formula to find out the area of reflected Sunlight to our eyes?  I ask, not because the formula is tricky; as a reminder, the date that Venus reflects the greatest amount is the designated date of greatest brilliancy.  Ten entries ago, I glazed over a link that I included in the text for Lambert's Law.  Without going into detail about it in this entry, letting you read it on your own time, I will mention that greatest brilliancy happens at a smaller phase than maximum brightness. 
   The first image shown here before the calculation and zoom-in, is a reminder of where Venus is in its orbit, and why we are seeing less and less of it illuminated each day; use the orbit thickness as a reminder for that.  The 12% illuminated, waxing crescent Moon about 6º away, is paired nicely with Venus as both set a similar altitude.

Detailed

    Refer back to my entry for April 14th for more information on that, as well as the formula for calculating lit surface area.  For this evening, compared to the 276 arc-seconds (") of area on the 14th, Venus is 290".  As it continues to approach us, its growth in angular size is still overriding its decreasing percentage illuminated.  This continues for awhile longer, yet eventually before inferior conjunction, Venus will wane quickly enough that the area starts to decrease faster.  Even so, its apparent magnitude will only decrease slowly, as it approaches us more quickly.  At the time listed in the images, Venus is a little over 45 million miles from us.  
   This second image with a field of 15', shows the planet with an angular size of 17' (radius) in its current waning crescent phase of 32%.  At magnitude -4.5, and Jupiter now too low towards the Sun's glare, Venus dominates the western sky in comparison to any other star near it.  Many of those stars, just barely visible to the eye alone, are tens of thousands of times dimmer than it in apparent magnitude.

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

Star movement rates near pole

Date: April 23rd
Time: 10:00 PM

Brief

   Yesterday I showed the location of the north celestial pole (n-c-p) with the celestial grid.  By doing so, it indicated one key thing: if stars were placed north of any of the gridlines that cleared the horizon, they would be circumpolar.  That part is obvious when looking at the lines.  What may not be as noticeable, is that the more circumpolar stars seen at a particular latitude, the less a viewer sees of the opposite hemisphere.  As shown a few dates back with constellations such as Scorpious, with the entire constellation clearing the southern horizon at transit, it makes me feel fortunate to beable to do most of my viewing from a mid-northern latitude, when close to home.

Detailed

   For today, I am still looking directly north, yet this time with the altitude/azimuth (alt/az) grid instead of the celestial one.  The altitude grid verifies how high we would be viewing when looking directly at the n-c-p. 

It is also a reminder of how far a star is from cardinal north (azimuth 0º) when it is before or after transit.  The closer a star is to the north axis, as the celestial grid showed in past entries, the less of a variance there is for that star in both azimuth and altitude.  When a star transits, that is when azimuth rate changes the fastest at most latitudes.  When very close to the n-c-p however, and about to transit, the altitude changes at its slowest.  The opposite holds true for both when the star is furthest from transit, changing rate extremes: azimuth changes the least when the star is the same altitude as the n-c-p, which is just under 6 hours before and after transit.
   To further show the following, I will include a second image of the both the alt/az and the celestial grids overlapping with a 2º field.  By doing so, and remembering that the stars follow the celestial gridlines, it can help understand the change of altitude and azimuth rates.  Polaris is the star that we will use for example, for both, being close enough to the n-c-p.

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

North Celestial Pole

Event Date: April 22nd
Time: 10:00 PM

Brief

   Several times so far in the 5 weeks that I have done blog entries, I have used a reference latitude of approximately 38º N.  Not only is this for my home-base observatory at Chabot Space & Science Center, but it is also one for overall, ideal viewing throughout the year; more of that is mentioned in the detailed.  Before that, I will show an image looking directly north.  Labeled are the north celestial pole (n-c-p), which at our latitude, is located at the altitude of precisely the same value.  The same scenario would be the case if we were looking in the direction of the n-c-p from the [global] north pole: 90º in latitude, 90º in altitude, which is straight up at zenith.  Therefore, the next time that you are trying to remember where Polaris is, currently about 41 arc-minutes from the pole, this may help.  Polaris is not only the closest easy-to-see star to the axis, but simply, a reminder of where north is when skies are clear enough to see it.

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

Detailed

   38º, give or take a few, is also a good latitude for other reasons: from here, all zodiacal constellations--the ones that the Sun passes the stars of each year--are easily visible above the horizon at their transit (highest) times; the shortest nights in the summer are still over 9 hours, including about 7 hours of dark enough skies; it is far enough from the global equator that humidity is not a large problem.  The latter scenario is important not only for clear sky-viewing, yet for better astro-photography conditions.  When taking photos, clear conditions are important, but we also want as low humidity as possible, for good transparency and seeing conditions.  The next paragraph further elaborates on these terms and other conditions for our latitude
  Good transparency doesn't only mean very clear skies; this is often because of very little water vapor in the air.  There are some times when skies can be very clear yet very damp, normally following a period of rain and when temperatures are cold; this is often the case before fog comes in, although not always the case.  By "seeing" being excellent, features such as the belts and zones on Jupiter can be contrasted in color much more easily, and we can see, as example, the divisions of the rings on Saturn.  Very importantly, we need dry enough skies so camera optics don't fog up. When it is windy, that leads to poor seeing conditions, causing a wavy turbulence visible in the air.  Of course, if a location is too far north, it means that (1) there are too many bitter cold evenings, with or without precipitation; (2) during late spring and summer months, there are not enough dark hours--if any--at the most extreme latitudes at certain times of year.

Scorpious' claws, head and "stinger"

Event Date: April 21st
Time: 4:00 AM

Brief

For one of my early entries last month, I mentioned Scorpious, and how its number of brightest stars and boundaries have changed since long ago.  Bordering zodiacal constellation Libra is faint overall, and its brightest stars used to belong to Scorpious.  They are labeled as the "claw" stars below.  Zubeneschamali (north) and Zubenelgenubi (south) once represented the claws of the Scorpion.  What happened, and why the change?? Find out here.  In short, if you don't find the change to your satisfaction, blame the Romans:
http://my.execpc.com/60/B3/culp/astronomy/Summer/scorpius.html

A then-and-now image of Scorpious and (then) Libra show, to indicate the change.
The image shows the current boundaries of Scorpious and Libra the way they are today, along with the stick figures.  Both are visible as dawn breaks in the west-southwest, for non-morning types who don't want to wake up before dawn to see them in darker skies.

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

Detailed

To easily see Scorpious, look for some of its brighter stars and the curvy "head", the heart Antares, which I mentioned last month, as a super-red giant star.  One extra star that I will label is a double star called Shaula.  This star marks the stinger at the end of the scorpion's tail, and can be seen much more easily from high elevations with no obstructions.  *If very high, from the window of a plane at night with the cabin lights dimmed, Shaula and the entire constellation can be seen more easily, latitudes south of 45º.  At low and mid-northern latitudes, it is easiest to see the figure out the window more hours of the evening, since it doesn't get as high as it does at southern latitudes.  Try this sometime, if you have a window seat facing south during a moon-free sky...it is extremely cool!

Jupiter, Venus & Pleiades setting

Event Date: April 20th
Time: 8:30 PM *local/6:30 *image 2

Brief

   As we view Venus and Jupiter in their bright glory, setting during evening twilight, the brightest open star cluster in the sky sets about equally separated by both planets, seen in between them: the  Pleiades Star cluster.  I showed the Pleiades earlier this season with darker skies while higher up.  Over the last 30 days, with the Sun setting later and moving north 12º since the equinox, the extra twilight time has meant a longer wait to see the cluster.  Besides that, it is setting about two hours later than it was 4 weeks ago.  As it, or any star of its stars get closer to the Sun under these conditions, it means a fast disappearance over the course of only the few weeks.  We will see Pleiades again in the morning easily starting in late May or early June, depending on how clear the horizon is from hills, houses and/or big trees.

Detailed

Although we have to spend about half of the spring season not seeing the Pleiades, southern hemisphere viewers have to wait a little longer time before seeing it again.  With a declination of 24.2º N, it spends slightly less time above the horizon than the Sun on the first day of southern hemisphere winter: late June through late September.  During the nights in the fall that we see the Pleiades throughout dark, not setting until almost Sunrise time 14+ hours after rising, viewers of similar latitudes south as our northern, only see it for 9 hours.
  The first image shows the celestial graph as seen from Chabot: close to 38º N.  The second shows the cluster with the grid very close to the horizon as the Sun sets.  As I did for an entry last week, I am using a location that is the same numerical latitude as us: Box Hill, Australia, using a time after the Sun sets and the cluster is visible.  With the Sun at similar altitudes below the horizon for each, by means of the shade of nautical-twilight blue, the altitude of the star cluster as well as the planets are less for the southern hemisphere than the northern.  This is because they are north of the Sun, whereas if they were south of the Sun, that hemisphere would have viewers seeing them higher.

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

Jupiter separates from Venus

Event Date: April 19th

Time: 8:00 PM

Brief

   Venus has been setting slightly later each evening for the last several months, as it (1) separated itself from the Sun and (2) the Sun has set later each evening since early December.  If you are big fan of seeing Venus high enough in the sky during twilight and still visible above the horizon shining very brightly after dark, April is the last good month to see both well.

Detailed

Although Venus is past greatest elongation, it has continued to gain northern declination, as it will until May 4th.  By then, at almost 28º, it will be the most north we see Venus for quite some time.  It is almost as far north as the Moon ever gets as well, because of the precession of its [orbit] nodes.  As a result of Venus being these extra degrees north, it still doesn't set until 3 hours, 49 minutes after the Sun, at 11:19 PM.  Despite this, we only see Venus easily above the horizon until about 10:30 in locations with lots of horizon obstruction, and 11:00 if minimal obstruction.  As a reminder, using the celestial grid in the image, Venus curves towards the horizon more gradually as it reaches it, in comparison to when it sets closer to the celestial equator.  Jupiter, about 10º less north follows a similar path, although the curve is slightly sharper.  Notice with the celestial equator itself, the angle with the horizon shown further to the left, is more angular and not so curvy, compared with the line closest to Venus.

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

   Finally, remember the March 13th, close encounter of Venus and Jupiter?  It happened shortly before I started this blog, although if you follow astronomy regularly with a clear sky in your area, there is no way that it could be missed.  In any case, while soon reach conjunction, Jupiter is now 26.5º separated with Venus; more than 10-fold than they were when they were 3º apart on that aforementioned March date.

Mars' celestial path through retrograde

Event Date: April 18th
Time: 8:00 PM

Brief

   I have shown Mars' celestial path for past entries, as it was in retrograde.  This evening's image shows a celestial path of the dates just prior to it going stationary, through this evening, as it starts to go prograde again.  The time-range of the path is a little over 2 1/2 months, starting in late January.  It will pick up speed in this direction, west to east against the stars, as we pull further away from it in orbit.  The image shows this zoomed out, with Leo's stick figure included.  The brightest star Regulus is still in binocular range of Mars at 4.3º, although the two will become further apart faster each day.  The constellation boundary of Leo shows at the bottom left, that just before retrograde, Mars had briefly left the Lion for about three weeks, moving against the stars in Virgo (not shown).

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

Detailed

   At the same time of Mars ending retrograde and beginning prograde, it has also dimmed at a slower rate; during the weeks of (near) opposition, it brightened and faded at its fastest.  At magnitude -0.3, it is still brighter than all except three stars seen from any latitude, and almost as bright as Alpha Centauri, which is too far south to see at this latitude.  Canopus and Sirius, with the latter visible to us during the late winter and early spring evenings, are brighter than Mars most of the time, which can vary depending on Mars' proximity to us and the Sun during opposition certain years.  Between now and late winter, we will see Mars east of the Sun, and the rate of brightening will continue to decrease.  Unfortunately well before its conjunction at about that time, Mars will be too far away to see features easily, and just appear as a orangish "blob" in a telescope.  With the eyes alone, we will see very little of no color starting later this season.

More moon node-talk

Event Date: April 17th
Time: 6:00 AM

Brief

   Yesterday, I showed the Moon, using it as a guide to find Neptune.  As a waning crescent, it is soon to fall into the glare of the Sun a couple days from now, and be too hard to see.  Besides, that, it will be reaching "new" phase, with its lit portion nearly completely turned away from us.  Looking at the image, the Moon is far enough south of the sub-horizon Sun: 12º to be approximate.  The Moon as a 13% waning crescent rises two hours before the Sun, at its given separation. 
In image one, is the Moon low towards the horizon, and its current phase.  Use the Moon to find much dimmer Mercury, which we used to find dimmer Uranus' location with optical aid yesterday.

Detailed

   On occasion at this time of year, at the same phase in about the same part of the sky, that the gap between Sun and Moon rise would be smaller: when the Moon is south of the ecliptic, and therefore, even further south of the Sun.  Because of the "precession of the nodes", the Moon is as much as 5 1/2º north and south of the ecliptic at two different parts of the sky.  Every 18.6 years, the Moon reaches these parts of the sky again at the same ecliptic latitude.  While in between, those extreme points move east to west in full circle; this translates to about 1.6º per month.  Since the Moon reaches the same part of the sky about every 27 days and 8 hours known as its sidereal period, it is either a little more north or a little more south, depending on where the nodes are--where its orbit meets with the ecliptic.  Since we see it north of the ecliptic in image two below, it is approaching descending node; where the ecliptic descends south of the ecliptic east of it. 

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

After the descending node finally reaches this part of the sky in late 2015-early 2016, the Moon's orbit continues to move south of the ecliptic at this point until 2021.  After that, each time that the Moon reaches this latitude, it will slowly become more and more north.Image two has Mercury unlabeled, while the orbit of the Moon, celestial equator and ecliptic are put in.

A little help finding Uranus and Neptune

Date: April 16th
Time: 6:00 AM

Brief

   Our most outer planets are starting to emerge from the Sun, as they move about a degree further from it each day.  The Sun is moving quickly north along the horizon as it rises, meaning slightly extra twilight time and starting a little earlier each morning.  With Uranus at magnitude 5.8, that is about the dimmest that we can see a star or planet under the darkest of skies with the naked eye.  Even under such sky conditions, the glare of twilight means that it will not be until about the time of the Summer solstice that Uranus falls under the following sky-postition characteristics: (1) high enough out of atmospheric pollution, and (2) separated enough from the Sun to see with the eye.  For either, sky conditions would need to be perfectly clear, of even haze.  Before Summer however, enjoy finding it with optical aid.  This morning, two other solar system bodies help us find it and Neptune: Mercury (magnitude +0.5) is 6º away from Uranus, seen to the right of it.  Since Mercury is moving in prograde motion again, it will catch up quickly with Uranus and be 2º from it in a week. 
An even brighter object is near Neptune: the Moon, at 5º away to Neptune's upper left.  In this first image, locations are shown for the Moon and three mentioned planets.

Detailed

   Once finding the Moon in a telescope, it and Neptune are precisely at right-ascension conjunction; they are the same celestial longitude, which makes it easy to slew from to it from the Moon if using an equatorial telescope; unlike an altitude/azimuth scope, an equatorial can be adjusted to a location's latitude, moving on one axis to measure right ascension, and one to measure declination.  Even with a small field of view, such as 3/4º which can still fit the Moon easily, they will still be close enough to conjunction to both fit in the same field, with the Moon centered in the field.
We will see Uranus all night along during the early fall during its next opposition.  Neptune is not visible to the unaided eye, and does not transit as high as Uranus for the next several years.  However, even as seen from a mid-northern latitude, its declination of 11º south means that when we see it transit under dark skies later this season, we will see it doing so at slightly over 40º -- nearly halfway between the horizon and zenith.  Over the next 56 years, Neptune will increase in declination moving more north.  The advantage of this, although still requiring optical aid, means that a powerful enough telescope will view it far enough out of atmospheric pollution to see its blue methane color more easily.
   In this second image, we see the celestial equator and ecliptic shown.  The former two remind us of each planet's declination.

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

Spring Arc during evening

Event Date: April 15th
Time: 9:00 PM

Brief

The Spring Arc, spanning from the northeast to the southeast in twilight-evening sky during this time of year, is easy to recognize if a person knows what stars to look for: those of the Big Dipper's handle, along with Arcturus and Spica.  The handle stars were shown when I featured the Dipper late last month.  Looking at the stars, they form a smaller arc-like shape of their own, which leads to the general direction of Arcturus: the brightest star of Boötes the Heardsman.  The figure continues to Spica, with Saturn (unlabeled) near it this year as a slight distraction; don't confuse the two, as Saturn is still too far in angular separation to fall into the flow of the arc.


Detailed

Despite the common saying of "make an 'arc' to Arcturus", in remembering that the star is part of the asterism, the name of helping us remember that so easily is coincidental.  Instead, Arcturus' name is derived from Greek as bear guardian.  However in Arabic, besides making up the arc, Arcturus and Spica both translate in English to uplifted one(s).

Besides the hyperlinks provided for the translations, see the names and cultural significance section of the Wikipedia article for more meanings of the names.
http://en.wikipedia.org/wiki/Arcturus#cite_note-arabicdict-15

Bottom line, none of them translate to "part of the spring arc"!  That is probably a good thing for a major reason: as a result of stars' proper motions, the spring arc stars used to--and will one day again--form more of a line, or a sharp curve. 
What is proper motion?  it is its angular change in position over time as seen from the center of mass of the solar system.  Find out more here, including rate of motion:
http://csep10.phys.utk.edu/astr162/lect/motion/proper.html

The image below shows the stars of the spring arc, and the Big Dipper stick figure, which reminds us where the handle stars are in relation to the "cup".

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

Venus nearing greatest brilliancy

Event Date: April 14th
Time: 8:00 PM

Brief

   Venus is approaching an important date during its post-greatest eastern elongation (g.e.e.) time in our evening sky.  Although it is gradually coming back towards the Sun and its apparition will become increasingly worse over the next month and a half, it is becoming a more attractive target to look at in a telescope: it is waning during its crescent phase, and increasing in angular size as it does.  While it does so, it is also catching up with us in orbit, and therefore becoming slightly brighter for the next two weeks.  Since it emerged from the Sun last fall, it has brightened by a larger percentage, from the high -3 range to mid -4 on the apparent magnitude scale.  As for the important date, Venus is approaching greatest brilliancy.  This is when we see the greatest surface area of light reflected to our eyes.  It doesn't mean that Venus is at its brightest however, as mentioned in the detailed section.  Before getting to that, here is Venus shown in its orbit, approaching Earth in our own.  Notice how it is now on the thicker, more visible part of the orbit, as we view its orbital path at an angle.  This evening, Venus is approximately 53 million miles from us, after being as far as 93 million miles from us (1 a.u.) as recently as February 16th.

Detailed

I will borrow some interesting text from the wikipedia link, for anyone confusing greatest brilliancy with greatest brightness.  Admittedly, I was one of them, until I read this!
http://en.wikipedia.org/wiki/Aspects_of_Venus
---------
Greatest brilliancy is often confused with "maximum brightness"; although they are related, they are not quite the same thing.  Greatest brilliancy is really a geometric maximum: it occurs when the apparent area of the sunlit part of Venus that we see from Earth is greatest.  Only if the luminance of Venus' apparent surface would be constant (i.e. the same at every point and at every phase) would the greatest brilliancy of Venus coincide with its maximum brightness. However, the reflection of sunlight on Venus more closely follows Lambert's law, which means that the maximum brightness occurs at a somewhat larger phase of Venus than its greatest brilliancy.
---------
   The two numbers to look for in calculating Venus' surface area, are (1) its percent illuminated, and (2) its angular size.  Once its angular size is researched in arcseconds, as software or the internet can also reveal, the formula for calculating the area is the same as that for any other circle: pi (π) multiplied by the radius-squared.  To keep it simple, we will keep pi at 3.14, rather than several decimal places extra.  Since the angular size is measured in diameter however, divide that by 2 first, and then apply the formula.  This evening, with Venus at 30 arc-seconds in diameter, the radius is 15.  The area therefore, is 3.14*15*15= 706.5 square arc-seconds.  Now, with the planet 39% illuminated this evening, multiply this in decimal form with 706.5, which equals 276 area arc-seconds , rounded up.

note: since angular measurements are not square, I redundantly reuse the word 'area' in the previous sentence. 

Until about 6 weeks before inferior conjunction, this area reaches its greatest value and therefore, greatest brilliancy.  As the borrowed text above states however, this often falls dates before or after the greatest magnitude that we see Venus.  With the eye alone, we would not notice, and the overall value in magnitude is still very close.
This second image shows Venus zoomed in, showing the 276 sq. arcs-econd surface area.  Use the numbers above again as a reminder, to understand the image, using a field of view of 8 arc-minutes.

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

Mercury's morning apparition: both hemispheres

Event Date: April 13th
Time: 6:00/6:30 (see detail)

Brief

   Although finding Mercury in the dawn sky now is still very challenging, it is getting slightly easier each week, as the planet brightens.  Whereas it as at perihelion in early March, it is now very close to aphelion, and as a result, brightening slower than average.  Aphelion happens tomorrow evening.  With Mercury coming slowly back towards the Sun, it means that the rate of brightening will slowly increase.  Take a look at Mercury below, now at magnitude +0.6, and notice via its orbit that it is nearing greatest western elongation.

 

Detailed

At this time of year, when Mercury is this far separated from the Sun, it is about as much so as it is all year.  The aphelion is more clear, giving it a current separation of almost 27º.  In the southern hemisphere at similar latitudes, viewers there get a treat that we do not here.  That is, when we see Mercury at its best apparition, similarly to how we have seen Venus over the last month, we only see it that way at perihelion and therefore, it only gets as high as 18º in altitude at locations with the best apparitions.  For southern viewers, they seen Mercury at the aforementioned 27º-- or as much as 28º, depending on how close it is to greatest elongation and the exact week of the spring. 
This 2nd image shows an image of the view from Box Hill Austrailia, which has a southern latitude of precisely the same as our northern one: 37º 49'.  Being in a different part of its time zone, I set the clock forward half an hour ahead, meaning Mercury can be seen even slightly higher without the Sun's glare getting in the way.

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

Never mind right now, that the ecliptic and celestial equator are reversed in direction; I will talk about that at a later date.  For now, just look at Mercury in orbit, reaching greatest elongation.  At our latitude, Mercury barely rises or sets more than 90 minutes before/after its best greatest elongation apparitions.  When further separated from the Sun as shown, Mercury rises or sets more than two hours (120 min) before/after the Sun...lucky dogs!  Some of the best views of Mercury happen just south of our equator, when the rise/set interval is closer to two hours, 30 minutes.

Saturn approaching Spica

Date: April 12th
Time: 9:44(.44) PM

Brief

   Saturn, which is almost at opposition, shines brighter than any of the stars in Virgo, where it is moving east to west in retrograde.  As we have watched it over the last two months, it has more quickly caught up to the hot, white-blue star Spica.  After being about 7º apart in late January and early February, when Saturn was stationary and started retrograde, the planet and star are now only a little 5º apart while still getting closer.  As Saturn ends its retrograde in about another two months, it will spend many weeks slightly under the 5º mark, before finally moving further through Virgo and not catching back up with Spica again for another 28 years.  Saturn's revolution period last about a year later than that, although we subtract a year or so for the back-and-forth time near a star.

Detailed

  Why the strange time listed at the beginning of this entry, and shown in the images?  It has little to do with when Saturn is high enough to see out of atmospheric pollution.  Instead, it marks when Spica and Saturn are exactly at the same altitude for the evening, as seen from our location.  The time for this changes slightly daily, as Saturn (1) rises about four minutes earlier each evening, and (2) changes gradually in declination in relation to Spica.  Look at the azimuth grid here, for an example of that.
 

There is no real significance of waiting for two naked-eye objects to be at the same altitude.  However in the daytime, if it is known, it could help find harder-to-see planets.  For example, a few weeks ago when Jupiter and Venus were near conjunction, Venus would become visible first just before the Sun set, in a telescope.  Jupiter, being dimmer, wasn't quite visible yet.  If a person with a telescope and a high magnification (therefore a small field of view) started on Venus, there was a small window of time for which he or she could move the telescope left and right; such would mean moving quickly from one planet to another without adjusting the telescope in altitude--just azimuth.  As I mentioned early in this series of journals, an altitude/azimuth (alt/az) scope is a good starter-telescope, and the most basic of telescopes are made this way: pivoting on a mount, in two different directions.  As a reminder of some of the most basic Dobsonian telescopes, see this link: http://en.wikipedia.org/wiki/Dobsonian_telescope
Some shown are very basic and not too expensive, while others motor controlled for tracking and therefore, much more costly.  If you are thinking of buying a telescope for a first time, see if that site works! 
As shown in this zoom-out, the planets at the same altitude of 21º 48.784'.

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

Pegasus' or Andromeda's star??

Event Date: April 11th
Time: 5:00 AM

Brief

Our sky is full of asterisms, and some make up simple shapes; we talked about one yesterday, with the Summer Triangle.  A little later, as the sky starts to lighten up, we see another clear the horizon completely: the Great Square of Pegasus.  The square is large, hence the "great" title, at 16ºx13º if measuring the sides anglularly.  It is not as big as the Summer Triangle, which it can be compared to with stick figures in the image.  However, the square is still big enough that in some parts of the sky equal in angular area, as many as three constellations fit.  At this time of year, the square rises in the east-northeast, and becomes high enough to see easily during the twilight sky by month's end.  It has four 2nd-magnitude stars of various distances from us.  Although it is not perfect in square, which would be very coincidental, it is close enough for us to recognize it that way.  The separation between each star is close enough to equal, for us to not call it the great rectangle of Pegasus; that takes too long to say, as it is.

Detailed

  The Great Square's stars' distances range from 99 light years away with Alpheratz, to Algenib's 335 light years away.  The distance of a light year is about 6 trillion miles, or 186,000 miles per second, times about 31.5 million seconds per year.  Notice that I used the word distance and not time measure a light year.  That is, the distance light travels over the course of a year.  Since I will be using the term throughout the entries,  with the shorthand as ly, it is worth keeping that in mind.
   One other thing that I must note, is that although Alpheratz is a star of the square, it is not--I emphasize--a star of Pegasus!  Why?  It is one of a constellation adjacent to Pegasus, marking that character's head, as opposed to the belly of the horse.  See image two, for what I am talking about; that one has the full stick-figure of both Pegasus and Andromeda, the chained maiden (or princess, some call her, as the daughter of King-constellation Cepheus and Queen Cassiopeia).

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

Note: If you click on Andromeda's hyperlink in the previous sentence, the website tells the myth of these characters.
I will mention more on the royal couple tomorrow as I will show both.  Notice below for now, how Andromeda's stick figure seemingly makes a "V" shape outward from head-Alpheratz, to create a female-ish dress--or gown--"skirt shape...which seemingly doesn't have a definite end beyond either her stick figure.
  If you have trouble seeing Andromeda at this hour, with the Sun rising not far east of it, look a little earlier in the morning if the horizon is clear, or try later in the spring with it rising about two hours earlier each month, separating a little more daily from the Sun by angular measurements.