The days are long and the nights are short around the summer solstice that occurred a few days ago at 03:34 PM PDT on June 20th, 2016. How late should one stay up to observe the stars in a dark night sky?
At this time of year, Vancouver resides in a twilight zone where we never reach a fully dark night sky. Instead, we experience different levels of twilight. Twilight occurs when the sun is below the horizon, but there is still light in the sky caused by the refraction and scattering of the sun’s rays in the atmosphere. Astronomers define three different types of twilight depending on how far the sun is below the horizon.
Civil twilight starts when the sun dips below the horizon and ends when the sun is 6 degrees below the horizon. There’s enough light to see, but people turn on their lights to drive a car, and the streetlights are starting to come on.
Nautical twilight begins when civil twilight ends and lasts until the sun is 12 degrees below the horizon. The sky can still be distinguished from the distant horizon when at sea, allowing sailors to take measurements of bright stars (hence the name).
Astronomical twilight ends when the sun moves below 18 degrees from the horizon. Night finally begins and you can observe the stars in a dark sky – assuming that there is no bright moon and there are no clouds are in the way.
But at Vancouver’s northern latitude (a bit above 49º north), the sun does not make it below 18 degrees from the horizon during June and during good chunks of May and July. We don’t experience night, with fully dark skies, during these months but remain in the twilight zone until sunrise the next day.
What can observers do? One option is to travel south – traveling a few hours south to Seattle lets you experience close to 1 ½ hours of night according to timeanddate.com. Another option is to observe bright objects that are visible during twilight such as planets, the moon, or bright double stars.
RASC Vancouver President, Suzanna Nagy, revived the “In Transit” presentation at the June 2016 member’ monthly meeting. “In Transit” is a short presentation of interesting astronomical events that are visible in the current sky.
Three Bright Planets
The Sun is Getting Less Active
Spotless Days Current Stretch: 4 days
2016 total: 4 days (1%)
2015 total: 0 days (0%)
2014 total: 1 day (<1%)
2013 total: 0 days (0%)
2012 total: 0 days (0%)
2011 total: 2 days (<1%)
2010 total: 51 days (14%)
2009 total: 260 days (71%)
Updated 10 Jun 2016
Reported by Adrian Mitescu, RASC Vancouver Secretary
On May 9, RASC Vancouver organized an outreach event for the Mercury transit. Four RASC Vancouver hosts (three council members and one volunteer) welcomed 170-200 people over four hours in the public plaza at 200 Granville St, Vancouver. We had three scopes: two with mylar filters, one with an H-alpha filter, one pair of binoculars with a mylar filter, and eclipse glasses. Several other council members stopped by at various times and provided backup support.
We set up right in front of the office tower in which The Vancouver Sun and The Province newspapers are located. Several reporters came down and interviewed us for two Vancouver Sun articles: one article with video and another article with photos.
Overall, we judge this event to be a success, with many “wow” moments and repeat customers. Some members of the public stopped by multiple times to see Mercury’s progress. From our conversations with those present, many people had never even looked at the sun through eclipse glasses before, much less solar telescopes.
Mars will be well placed for observing this long weekend as it will be at opposition on Sunday, May 22 at 04:10 PDT. Opposition occurs when the Sun and Mars are on exact opposites sides of the Earth. Mars is fully illuminated by the sun during an opposition and briefly rivals Jupiter in brightness during this year’s opposition. Mars reaches opposition every 26 months so the next one is not until 2018. Mars will be relatively large during this opposition, with an apparent diameter of 18.6 arc-seconds, because it is making its closest approach to Earth in 11 years a few days later on May 30th.
Mars is the only planet that reveals much of its surface features. Even a small 100mm telescope will show features such as dark shadings and the bright polar caps. Look towards the south around midnight – Mars will be the bright star-like object in the sky. But observing from Vancouver poses some challenges: Mars will appear no higher than 20 degrees above the horizon so the views may be blurred by turbulence in the atmosphere, and the weather forecast is predicting cloudy skies for the next few nights. Nevertheless, Mars will remain well positioned for observing for a few weeks after opposition so there is time to wait and hope for nights with clear skies and steady seeing.
Image from May 13th, 2016 using a Skywatcher ED100 Pro refractor, a ZWO ASI 224 camera and Antares 3X Barlow.
Scott McGillivray from the Royal Astronomical Society talks about the latest discoveries in space. This week: stargazers celebrate Astronomy Day in Vancouver, Mercury tracks across the sun’s path and researchers discover three earth-like planets.
If last year was any indication, the upcoming Astronomy Day and Science Rendezvous should be a busy one!
Things get underway at 11am and run until 3pm, with a list of activities that include:
Apollo rockets and Moon display
Jim Bernath and his hands-on science displays
Solar system displays, walk, and bean-bag toss
Three craft tables for children (alien figures, alien masks, and phases of the Moon with Oreo cookies)
Solar telescopes (outside the Trottier Observatory, weather-permitting)
Planetary Society display
Vancouver Telescope display
Our featured lecture will be Hubble’s 25 Years Odyssey, presented by Ray Villard of the Space Telescope Science Institute. There will be a 2pm talk for kids and a 7:30pm talk for the general public. Registration is required. Please follow this link for details.
We will also have a series of talks throughout the day. The talks will be in room 3150 on the East Concourse of the Academic Quadrangle.
What’s New in the Search for Exoplanets and Extraterrestrial Life
What’s up in the Global Space Community
The Creation and Formation of the Moon
It’s 2016 – Astronomy is More than Telescopes
The Trottier Observatory will also be open for tours throughout the afternoon.
Scott McGillivray from the Royal Astronomical Society talks about the latest discoveries in space. This week: NASA’s report on the loss of Mars’ atmosphere, Earth’s Aurora Borealis, SETI’s search for ‘Alien Mega Structures’.
Europe and Russia’s cooperation on a Lunar mission.
Additionally – a look at images submitted by viewers, and Howard Trottier’s first image from the SFU’s Trottier Observatory.