Archive for the 'Astronomy' Category

Mercury Rising

This morning, shortly after 6 am, I was outside watching the eastern sky as the stars above faded into the dawn. I was hoping for a rare glimpse of the planet Mercury. I did see it, and the tableau was interesting enough that I’ll be observing again tomorrow morning. Here is my simulation of what I expect to see so you can view the scene for yourself.

Mercury is the closest planet to the Sun, and in our sky it is usually too close to the glare of our star to be seen. We see its orbit almost edge on, so from the Earth, Mercury seems to dash from  one side of the Sun to the other. Sometimes it moves far enough away from the Sun so that it can be glimpsed in the sunset or sunrise.

Mercury at dawn 2016 September 29

Mercury rising on the morning of September 29, 2016
Click to see full size

The  Observer’s Handbook of the Royal Astronomical Society of Canada reports:

[Mercury] moves into the morning sky from the 20th to the 30th [of September 2016], reaching the greatest elongation on the 28th. This is the best morning apparition of the year for observers in the northern latitudes.

This image is a somewhat idealistic simulation. Today I found the sky was much brighter than the simulation, and the star-like objects that were visible in the brilliance of the pre-dawn sky were only Regulus in the constellation of Leo, and the planet Mercury. I recommend that you use binoculars to identify this part of the sky. Note: this is facing due east.

Even lower down than Mercury will be the 28-day-old crescent Moon.

Astronomical Simulation of Mercury Rising 2016sep29, showing the distance from the Sun, the horizon line, and the position of the Moon.

Astronomical Simulation of Mercury Rising on September 29, 2016
click to see full size

Seeing the almost-new Moon, plus Mercury rising just before the Sun is the unusual tableau that will make it worth going out to watch.

At this point, the old Moon is only 15º away from the Sun (which is still below the horizon.) This sighting should be valid for any mid-latitude in the Northern Hemisphere. The local time (British Columbia, Canada) of the simulation is 6:30 am.

Comet to pass very close to Mars

Some people find it scary that there are comets and asteroids out there that might hit a planet. Next week a comet — called Comet Siding Spring or C2013-A1 — will pass within 140,000 km of the planet Mars. Astronomically, that is a close encounter: the distance is about one third the distance from the Earth to our Moon. People have been wondering what the comet will look like from Mars. I thought that it might be equally interesting to see the event from the point-of-view of the Comet. Here is my simulation of the flyby on October 18 and 19. (It looks better in HD over at Vimeo.)

In both versions of the flyby, time is speeded up 3,000 times. While both views track the comet, the first is far enough from the comet that the orbit of the Earth (green) is visible and the geometry of the encounter can be seen. In the second view, the observer is on the surface of the comet facing the position of Mars and its moons, Deimos and Phobos. When the comet is closest to Mars, the disk of Mars would half-fill the field of view in a pair of binoculars. The planet would be an awesome site! No audio. It is quiet out there.

Eclipse 1979 remembered

In 1979 I was the director of the Manitoba Planetarium. Some friends believed that one of the reasons that I took that job was because I knew that on February 26 the Path of Totality of a solar eclipse included the City of Winnipeg. Previously, I’d traveled to see four eclipses. That very chilly morning, with Bill Guest, I was the co-host of CBC’s live coverage of the event. It has been decades since I’ve seen that program. I was pleased to find that it has been uploaded to YouTube. (The features that cut away from the program have been edited out.)

Edited on 2015 Oct 13 to add: Only this year, CBC posted this interview with Solar Magic producer, Earl Barnholden, and the broadcast co-host, Robert Ballantyne: VIDEO From the CBC archives: ‘The great eclipse’ of the sun, 1979

The old Montreal Centre, RASC, observatory

I was watching the charming movie, Helicopter Canada, made in 1966 by the National Film Board to celebrate the upcoming National Centennial.

In a brief scene showing Molson’s Stadium on Mount Royal, at the top of University Street on the McGill campus, I spotted the little observatory of the Montreal Centre of the Royal Astronomical Society of Canada.

The observatory is gone now. It is where I spent many evenings during the mid-sixties. There, I learned astronomy from the wonderful members of the RASC. And that led to a 20-year career in planetariums.
Old Montreal Centre, RASC, observatory on Mount Royal

Edited to add: Searching on the Internet, I found a picture of the 6-inch refractor that was housed in the observatory’s dome. I remember it was an accomplishment for me to be trusted to open the observatory and navigate the sky with that instrument. The image is posted at the site of Geof Gaherty, who in the 60s, was older than me and one of the Montreal Centre’s most accomplished amateur astronomers. (The site was but, since the death of Geof, it no longer exists. Here is a copy of the image that was at that site:) 

The Topham Refractor, Montreal Centre, Royal Astronomical Society of Canada. Date of image unknown, circa 1960.

Topham Refractor, Montreal Centre, RASC. I used it during the 1960s. Sometime later (the story that I heard goes) someone broke into the observatory and took the objective lens) It was never replaced. The picture looks like it was taken in the late 50s.


Reflections on the Dobsonian Telescope

Today I am remembering the great gift of astronomy that came to all of us from John Dobson, the inventor of the Dobsonian telescope. John died yesterday at the age of 98.

During my lifetime, one of the most profound developments in the technology of telescopes was made by John Dobson. In 1968 telescopes for non-professionals were either cheap and crummy, or precision optical and mechanical devices that were either very expensive, or required a sophisticated workshop to construct. Telescopes with a main lens that was more than 8 inches in diameter were almost too heavy for one person to carry, and they were beyond the means of most. Dobson changed all that.

John Dobson had a passion for showing people the sky. He founded the San Francisco Sidewalk Astronomers. And to see some of the great celestial celebrites, he realized observers needed a huge telescope. His discovery, and invention, was that if all you wanted to do was have an awesome nighttime view of galaxies, nebulae, and other wonders, you could strip away most of the technology that professional astronomers must have, and make a telescope with only a big glass lens and a few sheets of plywood. The cost was mainly that lens.

While I call this an advancement in technology, most of what he did was simplify the construction of a telescope, and re-think how it would be used. One of his (many) breakthrough discoveries had to do with the telescope bearings. He found that if the ‘scope moved by Teflon sliding on Formica, the coeficient of sliding friction was the same as the coeficient of starting friction. What that means is that if you have a telescope with no clock drive (to follow the stars), and had to push it by hand to keep the highly magnified target in the eyepiece, with Dobson’s bearings, the telescope would move smoothly and stop smoothly.

In 1985 a group of us build a Dob with a 17-1/2 inch mirror to be able to observe the return of Comet Halley. At the time, it was the largest telescope in Manitoba (in terms of the size of the lens). Here is the story of a group of us having our first glimpse of the Comet Halley. In the months that followed, thousands of people observed the comet with that telescope.

That Dobsonian telescope is now here on Bowen Island.

A group of people on Bowen Island observing Mars with the 17-12 inch Dobsonian telescope

A group of people on Bowen Island observing Mars with the 17-1/2 inch Dobsonian telescope

How to Observe the Solar Eclipse of 2012 May 20

Having travelled to see six total solar eclipses, a partial or annular eclipse is merely interesting. Nevertheless, observing some motion in the dance of the Sun, Moon and Earth still does thrill. After an amazing stretch of clear weather, rain and cloud has moved in to blanket the Salish Sea, so we will not be able to witness today’s eclipse. Below are some great sites that are promising to live-stream the event on the Internet. First, here is my computer simulation of the eclipse at 6 PM PDT. I was surprised to find that the Sun and Moon will be very close to the Pleiades during the event — of course those stars would not be visible even if the sky were clear.

Simulation: The Moon eclipsing the Sun near the the Pleiades at 6 PM 2012-05-20

Simulation: From the Salish Sea,
The Moon eclipsing the Sun near the the Pleiades at 6 PM PDT 2012-05-20

The web version of Sky and Telescope Magazine has published a list of sites where you may watch the annular solar eclipse online. <<Click link to open Sky & Telescope page.

Some of these sites may not be paying for a large bandwidth for streaming, so it if the connection  you choose seems slow, try one of the others.

Standard warning and fine print: if you can observe this eclipse, be advised that there is no time today when it is safe to look directly at the Sun. There are methods for safe observing, but you risk instant blindness if you don’t know them. If you are using optics, you could damage your equipment as well. 

Early Summer Star Maps

A star map - The sky at dusk - July 1 2011

The sky at dusk - July 1 2011

Summer arrives as I am writing this post. In this part of British Columbia we can expect the summer drought to begin soon. It means lots of sunny days and clear skies at night. This is when many people look up and begin to wonder about all those stars. I’ve made the following maps for Canada Day, July 1, but most of these stars will be visible for weeks.

Some of the most recognizable star-patterns in this part of the sky are not the constellations. High in the eastern sky, three bright stars from three separate constellations make up the Summer Triangle: Vega, Deneb, and Altair.

The Big Dipper is not a constellation (it is part of the Big Bear), but it is so well known that it is the major guide to most of the bright stars in this region. The two stars at the end of the bowl are sometimes called the Pointer Stars because a line between them extended across the sky leads to Polaris. It is useful to know about Polaris: if you look towards Polaris you are facing within 1-degree of true North.

In the other direction, follow the arc of the handle of the Dipper down to Arcturus and spike on down to Spica.

Constellation star map - midnight July 1 2011

Constellation star map - midnight, July 1, 2011

Here is a detailed constellation map for later in the evening when the sky is darker.

These maps are thumbs… click to see full size. You are welcome to print them for your personal use (not for publication).

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