2017 Week 26: (June 25-July 1)

This upcoming week will mark the halfway point of the year.  The double shadow transits of Jupiter's moons are done for the year which offered a great sight over the past 6 weeks.  The waxing crescent Moon appears this weekend to mark Eid al-Fitr for Muslims throughout the world.

Waxing Crescent Moon

The chart below highlights the significant events that can be seen in the sky throughout the week.

Date	Event
June 27	Regulus 0.03°N of Moon
June 30	First Quarter
July 1	Jupiter 3°S of Moon

Unfortunately there are not many exciting things happening throughout the week.  The bright breast bone star of Leo will be tucked in right next to the Moon this Tuesday evening.  Closer to the weekend every astronomer's favourite phase of first quarter will occur on Canada Day eve.  The Moon then moves over to be in conjunction with Jupiter the next day as we celebrate our nation's birthday.

We are still stuck in a rut for twilight over the next few weeks but the dark skies are on their way back in.  The Summer Triangle will be shining over our heads and we can pick out some great open clusters and planetary nebulae.  The Milky Way will make a great visual sight if you can get away from the city far enough to have pristine unpolluted skies.  The Rothney Astrophysical Observatory will host 6 nights of Milky Way observing in July and August.  Information for the July nights is given below.

https://ucalgary.ca/rao/event/2017-07-20/milky-way-nights-july-20-2017

I hope you have the opportunity to come out to see the sky.  Many people born today may never get to see the Milky Way due to the growing light pollution found throughout the world.  I am hoping to get a picture of the Milky Way this year but I'm not sure if my camera is quite up to it!  Good luck observing Jupiter and Saturn in the southern skies this week!

What is Twilight?

Calgary does not have true night between the third week of May and the third week of July.  The best we can manage between those times is astronomical twilight.  What are the different definitions of twilight?

There are three types of twilight defined below.

Civil Twilight
The Sun is located less than 6° below the horizon.  Civil Dawn/Dusk happens when the geometric center of the Sun is exactly at 6° below the horizon.

Nautical Twilight
The Sun is located between 12° and 6° below the horizon.  Nautical Dawn/Dusk happens when the geometric center of the Sun is exactly at 12° below the horizon.

Astronomical Twilight
The Sun is located between 18° and 12° below the horizon.  Astronomical Dawk/Dusk happens when the geometric center of the Sun is exactly 18° below the horizon.

When the Sun is 18° below the horizon it is officially Night.

It is well known that locations near the poles may experience days where there is no twilight and days that are completely night.

Many laws are incorporated in relation to civil twilight regarding driving, flying and even burglary.  Venus is typically visible during this time.  Nautical twilight is generally the time when sailors may use the stars to take measurements for manual navigation.  Once astronomical twilight is over and night arrives you will be able to see as many objects in the sky as your eyes and light pollution permits.  Deep-sky objects are able to be resolved and astronomers are happy.

To determine when these specific types of twilight occur in Calgary the following website is useful:

https://www.timeanddate.com/sun/canada/calgary

In the dead of Winter we get a whopping 12 hours of night.  However, the temperature and snow generally limit the joy of astronomy.  My favourite months for astronomy are March, April, September and October.  They offer a good balance of darkness and tolerable weather.

The image of a waxing crescent Moon and Venus below was taken Fall 2016 during nautical twilight.

Moon and Venus (Nautical Twilight)

2017 Week 25: (June 18-24)

This upcoming week marks the first day of Summer as discussed in the previous post about the solstice.  In the early morning sky before sunrise you will be able to catch Venus shining above everything in the sky except for the Moon.  Venus and the Moon will fit into the same binocular field this upcoming Tuesday so be sure to check it out.

Date	Event
June 20	Venus 2°N of Moon
June 20	Solstice
June 24	Super New Moon

10:24pm on the evening of Tuesday, June 20 will mark the beginning of Summer as the Sun will be observed to start decreasing in declination.  An interesting event happens next Saturday.  There will be a supermoon.  It is not advertised throughout the media because it is a New Moon supermoon.  You will not see a majestic bright rock in the sky, in fact you will not see anything.  However, since the Moon is at perigee (closest position to Earth in its elliptical orbit) at a New Moon the tides will likely be larger than normal.

There are other great sights to amaze you in the sky.  Jupiter can be seen in the south/southeast sky when it gets dark.  Saturn will be seen in the southwest sky and continue to shine throughout most of the Summer.  The great constellation of Hercules will be practically above our heads as it approaches midnight.  With binoculars or a telescope be sure to check out M13, the great globular cluster of Hercules.

M13

The unfortunate part of Summer is that it gets dark very late.  It seems as though twilight rules throughout the night.  As we get deeper into July our dark sky will start coming back and there will be ample opportunity to observe the Summer constellations.

In July and August there will be several evenings of open houses at the Rothney Astrophysical Observatory dedicated to observing the Milky Way.  Keep your eyes posted for more information as the time approaches!

What is the Summer Solstice?

The Solstice kicks off the beginning of summer and is the day with the most sunlight.

Where did the name 'solstice' come from?  It comes from the Latin noun 'Sol' meaning sun and the Latin verb 'sistere' meaning to stand still.  This makes sense as the Sun's motion in declination seems to stop and then change direction.

The Earth's rotational axis is tilted by approximately 23.4° from its orbital plane as it revolves around the Sun.  This causes it to seem like the Sun is changing elevation in the sky.  Around June 20 the Sun will begin its decent in the sky until around December 21 when the December solstice occurs.

Sun

There are a variety of myths associated with the Summer solstice.  It was known as the Midsummer Festival throughout much of the northern hemisphere.  The Church at the time converted this into St. John the Baptist day to commemorate the nativity of John (who was born approximately 6 months before Jesus denoted by Christmas).

The Midsummer Festivals were also about the importance of families.  Mother's Day and Father's Day are celebrated leading up to the Summer solstice.

The Greeks and the Romans held significant festivals on this day and served as a countdown to the Ancient Olympic Games.  It is known that the Maya and Aztec civilizations felt this day was of great importance.  Many of their architecture is aligned with astrological symbolism based on the solstice.  The Druids also placed great significant on the solstice and still gather at Stonehenge to mark the occasion.

If you chose to sleep at this time or read A Midsummer Night's Dream it is up to you.  Perhaps check out some news articles from celebrations around the world and see what different cultures still do to mark the longest day of the year!

2017 Week 24: (June 11-17)

We are approaching the summer solstice making evening observations difficult.  There are a few interesting events happening in the upcoming week.  Saturn will reach opposition at 4am on Thursday June 15.  A planet reaches opposition when it is on the opposite side of the Earth from the Sun.  The planet will be at its largest and brightest as observed from Earth.  The list of astronomical sights for the week is shown below.

Date	Event
June 15	Saturn at Opposition
June 16	Neptune 0.7°N of Moon
June 17	Last Quarter

Unfortunately, Saturn is low on the ecliptic for the next several years and more difficult to see in telescopes from our latitude.  However, Saturn's northern ring plane will be tilted to its maximum extent (26.7°).  This will allow for a great show of the ring divisions through a telescope if the seeing permits.  To see the great ringed gas giant look toward the southeast sky after the Sun has set.  You should see two bright objects, a twinkling red star and, further to the East, Saturn.  If you look at Saturn through household binoculars you may see that it is oblong in shape due to its rings.  The image below is my first try at capturing Saturn.  The seeing was quite poor due to its -22° declination.

Saturn

Neptune will be within the same telescopic field as the Moon on June 16.  It may be difficult to see over the brightness of the Moon and having to observe it very early in the morning.

The Moon will reach its Last Quarter phase this upcoming Saturday.  I always find the Last Quarter fascinating since I do not see it often in dark skies.  It will rise at 2am and be visible in dark skies until the Summer solstice Sun destroys it a few hours later.

Late in the evening look directly above and see the Summer Triangle formed by the bright stars Vega, Altair and Deneb.  Expect warm weather when these are sitting directly above your head!

Explore the Universe - Neptune

Neptune sits nearly 5 billion kilometers away from our comparatively diminutive planet.  Through a moderate sized backyard telescope it looks like an ordinary star.  However, if the seeing is good and you bump up the magnification you can see it has a disk.  It was very early on a summer morning in 2016 that I attempted to find Neptune.  I studied Aquarius in my star charts for at least 15 minutes determining to find λ Aquarii.  Neptune was only a half degree away from this naked eye star.  I did not have a red dot finder working at this time so I relied on a straight through finderscope.  It took 5-10 minutes to find λ Aquarii in my telescope.  I used my 25mm eyepiece with a 62.5' field of view.  I saw a dim grey object that did not twinkle among a few stars.  It was Neptune.  Amazingly I was able to capture it with my cell phone camera and the image is shown below.

Neptune

It may not look like much but it was hard work and determination that produced this blob of light.  Over the course of the next few months I watched as Neptune moved a few arcminutes each day.  It became a daily tradition when the sky was clear I would sketch the location of our furthest planet.  A log of the orbital motion is shown below.

Neptune - Orbital Motion

Neptune is named after the Roman god of the sea and its largest Moon is Triton.  Its radius is nearly 4 times that of Earth and its mass is 17 times.  It takes 164 Earth years to orbit the Sun, so in our lifetime we will only see it traverse half of its orbit.  It is interesting to note that its rotation is comparable to that of Earth.  Neptune rotates once every 16 hours.  Rings were discovered around the planet when I was two years old back in 1984.

2017 Week 23: (June 4-10)

June is now in full swing and the skies get dark very late into the evening.  I was out last night and I could not locate Polaris until after 10:30.  I worked hard on leveling the mount and using my polar alignment scope to align everything to North.  For some reason I had to slew the telescope a little more than I would have thought to find my calibration stars.

This upcoming week does not have anything too exciting.  The next Full Moon will be on Friday and it occurs close to when the Moon is at apogee.  This is sometimes referred to as a 'Micromoon'.  Unlike a 'Supermoon' it is not well advertised on the news.  The difference in size between a 'Supermoon' and a 'Micromoon' is only about 4 arcminutes.  Since Full Moons occur once a month and you cannot see the two Moons together in the sky it is hard for human perception to notice.  Since the Moon orbits in an ellipse there are times when it is closer to the Earth (perigee) and times when it is farther (apogee).

Supermoon vs. Micromoon

The below chart shows the events occurring throughout next week.

Date	Event
June 9	Full Moon (Micromoon)
June 9	Saturn 3°S of Moon
June 9	Jupiter Stationary

Saturn will be just South of the Micromoon on Friday evening.  If you can see the southern sky from your house check it out around 11:30 in the evening.  Saturn is bright at this time of year as it reaches opposition on June 15.

Unfortunately the seeing was bad last night so it was difficult to get a good image of our ringed gas giant friend.  Also, I only have 2 hours of experience with photoshop at the time of writing.

Saturn

An interesting thing happening in the sky on Friday will be with Jupiter.  Jupiter will switch to prograde motion and continue its trek East in the sky compared to the background stars.  Jupiter had been undergoing retrograde motion (moving West compared to the background stars) since February 6.

Jupiter is higher in the ecliptic than Saturn so suffers less from poor seeing.  An image below is from last night.

Jupiter

Enjoy the summer weather and look up to the sky if you are out late at night!