AstroNotes March 2020

Editor’s Message . Ottawa Skies . The Antikythera Mechanism . Jim Thompson . Monthly Challenge Objects . Submitted Images . Estelle’s Pick of the Month . Announcements . Members in the News . Carp Star Parties . FLO Star Parties . Next Meeting . Centre Information







Download PDF version: 


The Newsletter of the Ottawa Centre, RASC

Volume 59 – No. 3 – March 2020

Editor’s Message

Well for all you winter weary watcher of the sky, we have made it to March: the season of robins, crocuses, galaxies and Messier Marathons. The weather is starting to warm up nicely and it is now safe to venture outside after dark without too much fear of freezing before you have your equipment setup and aligned. On Friday, March 20 we will be having our monthly Members Star Party at the Fred Lossing Observatory (FLO). This is the perfect weekend to catch all the Messier objects in the sky in one night. It is also the perfect night to sweep the winter dust from your telescope and join us for a good night of observing. If you have attended one of our FLO Star Parties, you know how much fun they are. If you haven’t, come find out what you have been missing.

This month we have an interesting article from Richard Taylor on the Alethiometer. Oh, wait a minute, that’s in the book I’m reading Julia. Richard’s article is on the Antikythera Mechanism, an ancient astronomical artifact found in Greece 120 years ago. Read how this amazing item worked at predicting lunar and planetary positions over 2,000 year ago!

In our ongoing series of member profiles, this month we feature Jim Thompson. Over the past few months Jim has given the meeting a couple of presentations on astronomical filter that we will be reproducing in the April AstroNotes.

As always, I hope you enjoy this issue and if you have any comments, criticisms or contributions, please share them with me.


Clear skies


Ottawa Skies

By Dave Chisholm

Full super moon on March 9 – known as the Full Worm Moon, Full Crow Moon, Full Sap Moon…

Comet PanSTARRS C/2017 T2 will be visible in the evening skies. Its perihelion is on May 8th at which point it should be magnitude 8.


Rise/Set 06:07/17:00 -> 06:04/16:59

March 24 – Greatest Western Elongation

Look for the planet in the eastern sky just before sunrise.


Visible early evening.

Rise/Set 08:12/21:44 -> 08:18/23:42

March 24 - Greatest Eastern Elongation (At highest point above the horizon.)


Visible just before sunrise.

Rise/Set 03:50/12:20 -> 04:08/13:04


Visible just before sunrise.

Rise/Set 04:25/13:10 -> 03:43/12:35


Visible before sunrise.

Rise/Set 04:54/13:53 -> 04:04/13:08


Visible first part of the night.

Rise/Set 08:38/22:18 -> 07:44/21:27


Not visible.

Rise/Set 07:04/18:16 -> 06:08/17:24


The Antikythera Mechanism

By Richard Taylor

You have probably heard of Ptolemy’s model of the solar system in which the Earth was the center with the Sun, Moon and planets orbiting around it in a complicated system of circles and epicycles. What a relief that Copernicus threw that away and gave us a much simpler Sun-centered solar system! Nice, but not true. Copernicus moved the center, but couldn’t let go of the perfect circle, so his model included epicycles, too. It wasn’t until Kepler re-examined it all and came up with the idea of ellipses and non-uniform speed that we finally had an accurate model of planetary motion.

As a high school Physics teacher, I often recounted this bit of history as a lead-in to a unit of study about gravity and orbits. But two things puzzled me about the old models:

  • How, exactly, could a circle and an epicycle produce a motion that closely matched the actual motion of the planets?

  • How did the ancient astronomers actually do the calculations?

The answers to these puzzles were revealed to me last October on a trip to Greece and particularly a visit to the National Archaeological Museum and the Kotsanas Museum of Ancient Greek Technology in Athens. The answer to the second puzzle comes first: the ancient Greek astronomers apparently had access to a considerable level of technology, including sophisticated mechanical calculators made with bronze gear systems. Sadly, almost all of those calculators have been lost to corrosion or were melted down to make weapons. The writings that described them were burned, or lost, or were translated so many times that their original meaning was obscured.

In 1900, some sponge fishers working off the coast of the island of Anitkythera discovered the wreck of a ship that seems to have gone down around 70 BC. Over the next few years, many important artifacts were brought to the surface. The salvage included some bits and pieces of heavily corroded bronze.

For most of the 20th century, these remains were ignored by archaeologists and historians because they were too difficult to interpret, other than seeing that it was a gear-based device for calculating astronomical cycles. Even x-ray examination in the 1970s and 1990s didn’t help much. Neither did Erich von Däniken suggesting in his 1968 book Chariots of the Gods, that it was evidence of aliens visiting the Earth and giving humans some of their technology. Finally, the technology of this century (high resolution CT scans) allowed researchers to examine the gears and inscribings in sufficient detail to reconstruct the device.

The results are mind-boggling. The Greeks of 2000 years ago had a level of technology, mathematics and astronomy that was unmatched for about 1500 years afterwards. Rather than blaming aliens, I think it is more useful to contemplate how intelligent and resourceful humans can be, and also how destructive and close-minded humans can be. When we look around at our current level of science and technology, we sometimes are tempted to think that we (current humans) are more intelligent than humans of the past. We glorify “progress” and sometimes even “evolution” as being a linear process of improvements through time. But as I learn more about history, I am continually having my nose rubbed in the opposite. The most intelligent people of the past were at least as intelligent as people today and came up with some truly amazing ideas and inventions using far fewer resources than we have now. But progress has never been linear. Instead, there has been an ongoing war between people generating better ideas and technology and people who destroy and refuse to accept ideas that contradict their beliefs. It frightens me that current events show that this war is far from over. Just think how puzzling it will be to future archaeologists when they dredge up a single, heavily corroded smart phone two thousand years from now!

So, what did the Antikythera machine actually compute? Well, the more it is investigated, the more is learned about ancient Greek astronomy. Their observations of the Sun, the Moon and the planets must have included records over very long periods of time, because they knew about some cycles that only repeat after a very long time. For example, the Antikythera machine had a wheel and pointer that would have predicted eclipses based on the Exeligmos cycle which is equivalent to three of the more commonly known Saros cycles. The Exeligmos cycle predicts that solar and lunar eclipses will repeat AT THE SAME LOCATION, every 19,756 days (just over 54 years.) The gearing of the machine uses this value of the period; our current understanding of this period is that it is 19755.96 days. It should be obvious that astronomers wouldn’t notice such a lengthy cycle without having access to detailed and accurate records of observations for several repetitions of the cycle.

Another example of what the Antikythera machine calculated is the other thing that has puzzled me about ancient astronomy: how epicycles simulate the motion of the moon and planets. I was very happy to be able to buy at one of the museums a plastic model of one part of the Antikythera machine that demonstrates some of this.

Thanks to the work of Kepler and Newton, we now know that orbits are generally elliptical and that orbiting bodies move slower when farther from the central body and faster when closer. This was a very difficult idea to come up with because the orbits of most celestial objects are almost circular, and the changing distances are extremely difficult to observe and measure. We hear a lot of hype these days about “super moons” when the full moon coincides with the moon’s perigee, but most astronomers know that there’s very little difference in the visual appearance of a full moon and perigee and a full moon at apogee.

However, the varying speed of the moon in its orbit was definitely observed by the ancient Greeks and they came up with a mechanism that could describe and predict it with pretty high accuracy. I’m a great fan of Lego, particularly the subset known as Technics, so I’ve been playing with gears and gear ratios for a long time. When gears with different sizes and numbers of teeth interact, they will turn at different speeds with a ratio that depends on the ratio of the number of teeth. Gears that are connected with a common axle turn at the same speed even when they have different numbers of teeth. Clocks include sets of gears to make a combined gear ratio of 1:60 so that, for example, the minute hand and the hour hand can rotate with this ratio of speeds. But with all of these gear ratios, the gears each turn at a constant rate, not a rate that changes as they go around. How could a varying speed be modelled?

The trick is to mount two gears on top of each other but with their axles slightly displaced from each other, and to get one gear to turn the other using a pin mounted on one gear that slides in a slot on the other gear. When the pin is close to the axle of the second gear, it pushes that gear at a faster angular rate than when it is far from the second gear’s axle. This is the mechanical equivalent of Kepler’s idea: closer faster, farther slower. In my souvenir model, the gears are made of transparent plastic so that you can see one gear through the other, and both gears are linked to other gears with the same number of teeth but including “moon pointers” that help to compare a constant speed moon with a varying speed moon. You can see how this works on my YouTube video:  The darker spot on the smaller gear represents an imaginary moon rotating at a constant angular speed. The brighter spot on the end of the pointer represents the real moon rotating at a varying angular speed. Look at the pin and slot mechanism on the other two gears that are driving the moon gears. Notice how the brighter moon speeds up when the pin is at a small radius and it slows down when the pin is at a larger radius.

Not shown on this model is a second non-uniformity of the moon’s motion: slow precession of the moon’s orbit. This was also known to the Greeks and modelled by placing the previously demonstrated mechanism on a larger, slowly rotating platform.

This picture from the National Archaeological Museum in Athens shows a larger portion of a reconstructed machine, including the rotating platform and the gear and slot mechanism.

As mentioned earlier, the existence of this mechanism provides evidence that both the astronomical and the technical knowledge of the ancient Greeks were extensive and impressive. However, detailed study of the parts show that this is NOT evidence of some super-human intelligence nor technology. For example, there are non-uniformities in the degree markings on the scales that indicate that they were inscribed by successive division of arcs “by eye”. The complexity of the work shows that there must have been considerable infrastructure in bronze-making and gear making, but the use of triangular teeth shows that they had not discovered the best geometry for efficient transfer of movement. The meshing errors were almost certainly larger than the mathematical errors in the gear ratios. There are also some places where the CT scans show parts that were broken and subsequently repaired.

So, what happened to this astronomical and technical knowledge between then and now? There was a long hiatus in European history during which there was little progress in these areas. Much of the knowledge was lost - books and documents were burnt, bronze was valuable for making cannons. However, some of the ideas were preserved in the Arabic world. As we know from the plethora of Arabic names for celestial objects, this was where astronomical observation and documentation continued. There is also evidence of an on-going tradition of mechanical clock making in the Arabic countries.

The internal workings of a water-clock. From ‘The Book of Archimedes on the Construction of Water-Clocks’ in Arabic.’s-most-fantastic-clocks

Now that we do have a good understanding of the Antikythera Mechanism, numerous modern craftspeople have built copies of it. If you are interested in metal crafting, there is an excellent series of videos about how a brass model is being built.


The Antikythera Mechanism Research Project, <>

Wikipedia contributors. "Antikythera mechanism." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 29 Feb. 2020. <>

Museum of Ancient Greek Technology, Kostas Kotsanas <>

Marchant, Jo, “Decoding the Antikythera Mechanism, the First Computer” Smithsonian Magazine, Feb. 2015. <>

de Solla Price, Derek J., “An Ancient Greek Computer”, Scientific American, June 1959

Jim Thompson

We asked Jim Thompson to tell us a little about himself and his passion for amateur astronomy as part of our on-going series of biographies of members.

Here is how he answered our questions:

Could you give our readers a little bit of info about your background?

I was born and raised in the Belleville, ON area. I moved to Ottawa in 1989 to attend Carleton University, from which I earned a B.Eng. (Aerospace) in '94 and an M.Eng. (Aerospace) in '96. My specialty was Propulsion and Aerodynamics.

Immediately after finishing my graduate studies, I landed a job at a small engineering company in Ottawa called W.R. Davis Engineering Limited. The company has worked hard over the past 30 years to position itself as the world leader in engine exhaust infrared signature suppression, with application to ships and aircraft. In the last few years we have applied our stealth technology to the offshore petroleum industry in order to solve problems with engine exhaust management. I am presently the manager of the Aero/thermal and Performance Group at DAVIS, with a team of five engineers reporting to me.

I live in central Ottawa with my wife and two kids.

How did you get into amateur astronomy?

Growing up I was exposed to a lot of outdoor pursuits: camping, fishing, hiking, boating, dirt bikes, snowmobiles, etc. Having spent so much time outside as a kid it is no surprise that I acquired an interest in astronomy at a young age. I spent many a summer night through the late 1970's lying in a field at Four Loons campground on Weslemkoon Lake, staring up into a pristine dark sky. My interest in astronomy continued through high school, as did my interest in math and science in general. A number of my school projects had an astronomy focus, including a Grade 11 science fair project where I laid out a manned mission to Saturn on a spaceship powered by a tokamak-style fusion reactor.

What excited you about it?

As a young boy, and even through high school, I was a very quiet shy kid. Astronomy was a pursuit that was well suited for a socially awkward boy who preferred to be by himself. I imagine that for everyone there is some particular event that really cemented their love of astronomy. For me it was the NASA Voyager missions. I can still remember the excitement of visiting my grandparents back in the '80s, eager to see if their monthly issue of National Geographic magazine had arrived yet. The Voyager mission images published in that magazine were amazing to me; these were pictures of other worlds, worlds that I had seen with my own eyes through my small 60mm telescope. I still get excited when I see the latest batch of images downloaded from the many robotic missions that are ongoing today.

What excites you still today?

If one has any sort of curiosity about the world around them, it is hard to not be excited about astronomy. The pace at which new discoveries are being made has not slowed since the Apollo or Voyager eras. Some discoveries are fundamentally changing our understanding of how the universe works and our place in it. On a more personal level, I am excited when I have an opportunity to share my little bit of knowledge and experience with somebody else. Whether I am sharing a view through my telescope with my kids or talking with fellow RASC members about my latest observing session, the sensation of seeing the light in a person's eyes switch on is a great feeling.

What aspects of the hobby have particularly held your interest?

Being an engineer, I have a keen interest in the technical side of the hobby (i.e. the gadgets). My engineering background makes it very difficult to look at a new piece of equipment and not think to myself: "well, how does that work". I am especially interested in applying my skills to answering technical questions on behalf of the larger amateur astronomy community. This is what led to my extensive experience with astronomical filters, and astro-video cameras. I have published numerous test reports and magazine articles on these subjects over the years. Right now, for example, I am writing up an extensive test report comparing various brands of multi narrowband filters.

What kinds of observing do you do?

The bulk of my observing is done using a camera, a technique called Electronically Assisted Astronomy. I have given a talk at a monthly RASC meeting on the topic. I don't have a lot of free time, so when I observe I am limited primarily to doing it from my backyard in the Alta Vista part of Ottawa. Instead of limiting myself to visually observing only the objects that can be seen through the light pollution, I have embraced the use of a video camera in order to remove these restrictions. I can essentially observe whatever I want, any time of year, from the comfort of my rec room. I also like EAA in outreach applications such as on Astronomy Day or when I go camping with my kids' scouting group. It is so much more effective to have the kids looking at an object together on a screen than individually through an eyepiece.

What connections has the hobby made to the rest of your life?

There have been a few fleeting connections to my work, mostly relating to optics. The biggest connection to the rest of my life though is through the friendships that I have made as a result of the hobby. My membership in local astronomy groups like RASC and the OAOG has introduced me to a fascinating group of people that I would not have met otherwise.

What advice would you give to novice amateur astronomers?

Probably the best thing you can do is get out and meet people with the same interests as you. Like I already mentioned, there are many fascinating people in our local amateur astronomy community. You will not find a better source of knowledge on the topic, so make an effort to get out to events and meet some of these people. Another piece of advice I have is to be patient. You should not expect to be an expert after only a couple months or a year in the hobby. Part of the enjoyment in the hobby is encountering new problems, and with the assistance of your fellow amateurs, solving those problems. The hobby has many different aspects and specialties to choose from, so if one avenue is not working for you, try something else.

Monthly Challenge Objects

By Oscar Echeverri

Submitted Images

Comet ATLAS C2019 Y4 near M97 and M108 by Paul Klauninger

Estelle’s Pick of the Month


Please note that Howard Simkover will again be presenting to the Ottawa Field Naturalists Club.  The topic for the March 10 presentation will be "Distant Worlds of the Solar System - Pluto and the Search for Planet X". A summary of the presentation is attached.

If you wish to attend, the OFNC meetings are held at the KW Neatby Building, 960 Carling (free admission and open to the public;

Distant Worlds of the Solar System - Pluto and the Search for Planet X For thousands of years, humanity was aware of five bright planets in the night sky. But in the 18th and 19th Centuries, astronomers found two additional planets beyond Saturn - Uranus and Neptune. After Neptune's discovery in 1846, astronomers wondered if there were other planets hiding in the far-flung depths of the outer solar system. Perhaps there was a "Planet X" out there? Success came in 1930 when a 24-year-old astronomer who grew up on a farm in Kansas discovered the 9th planet, Pluto. Pluto has always held a unique fascination for us. Many people were bitterly disappointed when in 2006 it was downgraded to a 'dwarf planet'. In July 2015 NASA's New Horizons spacecraft flashed through the Plutonian system, taking incredibly detailed photographs of this distant world and its retinue of moons, revealing their astonishing beauty and complexity. Howard Simkover, who has produced shows for the Montreal Planetarium, will speak about Pluto and the search for planets in the outer solar system.

International Astronomy Day is coming!! Make your calendars.


  • Saturday, May 2


  • Saturday, September 26

Members in the News

Congratulations First Prize Winner of the Photo Contest!

Congratulations to Jim Thompson for winning first prize in our First Annual Photo Contest! Jim used Omega Filters to capture three images of our vast galaxy in his very own backyard in Ottawa, Canada, and Casper, Wyoming. Scroll down to see Jim's three entries!

#1 Sun-CaK captured using a 98mm apochromatic refractor with 4x Barlow lens for a total focal length of 2470mm, and a ZWO ASI290MM planetary imaging camera. The image is a stack of the best 200 frames from a capture of 3000 using an Omega Optical Calcium-II K (393.4nm) bandpass filter with one Angstrom bandwidth.

Entry #2- Solar Eclipse captured using a 135mm camera lens with aperture set to f/4, and a ZWO ASI290MM planetary imaging camera. Each image in the composite is a stack of the best 20 frames from the capture of 100. Filter used is an Omega Optical Calcium-II K (393.4nm) bandpass filter with one Angstrom bandwidth.

Entry #3 The object pictured is NGC6992, part of the Eastern Veil Nebula, a supernova remnant in the constellation Cygnus. Captured using a 10" Ritchey-Chretien telescope reduced to f/6.5, and a ZWO ASI294MC deep-sky imaging camera. The image is a live stack of 38 x 10sec unprocessed frames. Filter used was a combination of a commercially available light pollution filter stacked with a custom Omega Optical blue and deep-red blocking filter. The end result stacking the two filters was a dual narrow passband filter with passbands at Hydrogen Beta (486nm)/Oxygen III (501nm), and Hydrogen-Alpha (656nm).

Carp Star Parties

  • Here is the schedule for our Public Star Parties for the summer. Thanks Paul.

    • Friday, May 22

    • Friday June 19

    • Friday, July 17

    • Friday August 15

    • Friday, September 12

    • Saturday, October 10

FLO Star Party Dates for 2020

  • Our Ottawa Centre’s Members’ Star Parties at the FLO will continue this summer. If you haven’t attended before, be sure to mark at least one of these dates on your calendar. You are welcome to bring family members or a guest. The GO/NO GO call will be made on the Centre mailing list, about noon the day of the star party


  • Saturday January 25 – Waxing Crescent Moon, 1.1% illumination NO GO

  • Friday February 21 – Waning Crescent Moon, 2.8% illumination - GO

  • Friday March 20 – Waning Crescent Moon, 10.8% illumination

  • Saturday April 25 – Waxing Crescent Moon, 7.3% illumination

  • Saturday May 23 – Waxing Crescent Moon, 1.4% illumination

  • Saturday June 20 – Day before New Moon, 0.2% illumination

Next Meeting

7:30 PM Friday April 3, 2020 at the Canada Aviation and Space Museum (directions). Note there is a $4.00 parking fee for museum parking. The meeting runs until 9:30 pm

PLUS: all our regular meeting features: Ottawa Skies, 10-minute Astronomy News Update, Observation Reports and, of course, the beloved Door Prizes!

All RASC monthly meetings are free and open to members and non-members alike. Refreshments will be available, and this will be a wonderful opportunity to meet new friends who share a common interest and chat in a relaxed, stimulating and fun environment. Please join us!

Centre Information

To subscribe (or unsubscribe) to our members-only discussion list ( ) please contact .

The Ottawa Centre 2020 Council

President: Mike Moghadam (
Vice President: Stephen Nourse
Secretary: Chris Teron (
Treasurer: David Parfett (
Centre Meeting Chair: Dave Chisholm (
Councillors: Carmen Rush, Gerry Shewan, Jim Sofia
National Council Representatives: Karen Finstad, OPEN
Past President: Tim Cole

2020 Appointed Positions

Membership: Art Fraser
Star Parties: Paul Sadler
Fred Lossing Observatory: Rick Scholes (
Light Pollution Abatement: OPEN
Public Outreach Coordinator: Jean-Sebastien (JS) Gaudet
Hospitality: Art & Anne Fraser
Stan Mott Astronomy Library: Estelle Rother
Ted Bean Telescope Library: Darren Weatherall
Webmaster: Mick Wilson (
AstroNotes Editors: Gordon Webster & Douglas Fleming (