Hogg and Seager at RASC 2020 GA

RASC General Assembly June 5 to 7 2020 Executive Plaza Hotel Coquiltam BC

Two Canadian women astronomers are featured prominently at the Hogg Memorial Lecture that is part of the RASC 2020 General Assembly in Vancouver. The Hogg Lecture is named in recognition of the lifelong contributions of Dr. Helen Sawyer Hogg towards increasing public awareness and appreciation of the Universe. It is held annually alternating between the RASC General Assembly in even-numbered years and CASCA’s conference in odd-numbered years. Dr. Sara Seager is delivering this year’s Hogg Lecture during the RASC 2020 GA on June 6th, 7:00 pm at Simon Fraser University. The lecture is free and open to the public – register now.

Dr. Helen Sawyer Hogg

Dr. Hogg was a notable woman of science in a time when many universities would not grant scientific degrees to women. As an astronomer, she is recognized for pioneering research into globular clusters and variable stars.

Helen Sawyer Hogg at Telescope
Helen Sawyer Hogg. beside her beloved David Dunlap 74-inch telescope in Toronto

Hogg did graduate work at the Harvard Observatory where she worked with Dr. Harlow Shapley measuring the size and brightness of globular clusters and publishing several papers. Hogg received her master’s and doctoral degrees from Radcliffe College because, at that time, Harvard refused to award graduate degrees in science to women.

In 1931, she and her husband Frank set out in their Model A Ford for Victoria BC and the Dominion Astrophysical Observatory where a position awaited Frank. There was no opening at the DAO for Helen, but the Director gave her the use of the 72-inch telescope to further her research. The couple moved to Toronto’s “new” Dunlop Observatory in 1935 where Hogg continued her study of variable stars in globular clusters.

Her successful professional career was matched by her generous community activities, many of them reflecting her efforts to ensure that

“The Stars Belong to Everyone”

Helen Sawyer Hogg

which is the title of one of her popular books and adopted as the theme of the 2020 GA. She prepared a weekly astronomy column for The Toronto Star for 30 years, starred in an astronomy TV show, and wrote numerous articles for the Journal of the RASC. She was the first woman president of the physical sciences section of the Royal Society of Canada, as well as the first female president of the Royal Canadian Institute, and a national RASC president.

Helen Sawyer Hogg Plaque
Canada Museum of Science and Technology, plaque to Dr. Helen Sawyer Hogg.

Dr. Hogg was promoted to a Companion of the Order of Canada in 1976 and posthumously inducted into the Canadian Science and Engineering Hall of Fame. RASC included her among 15 eminent astronomers that were named as Honorary RASC Members.

Dr. Sara Seager

The Hogg lecture at the 2020 General Assembly will be given by Dr. Sara Seager. She is a planetary scientist and astrophysicist at the Massachusetts Institute of Technology. Dr. Seager has pioneered research in the field of exoplanet atmospheres and now, like an astronomical Indiana Jones, is on a quest seeking the field’s holy grail, another Earth-like planet, searching for life by way of exoplanet atmospheric biosignature gases.

Seager’s research has introduced many new ideas to the field of exoplanet characterization, including work that led to the first detection of an exoplanet atmosphere. She was part of a team that co-discovered the first detection of light emitted from an exoplanet and the first spectrum of an exoplanet.

The light blue region depicts the “conventional” habitable zone for planets
Image credit: Sara Seager, Science 03 May 2013: Vol. 340, Issue 6132

Seager’s research now focuses on theoretical models of atmospheres and interiors of all kinds of exoplanets as well as novel space science missions.

Her Hogg lecture on Mapping the Nearest Stars for Habitable Worlds is free and open to the public.

She is the author of two textbooks and has been recognized for her research by Popular Science, Discover Magazine, Nature, and TIME Magazine. Seager was awarded a MacArthur Fellowship in 2013.

Professor Sara Seager was born and grew up in Toronto, Canada. Among her first memories is a trip to a “star party” with her father, to see the moon through a telescope—spectacular! Professor Seager graduated from Jarvis Collegiate Institute, a 200-year old public high school known for its science education. During high school she was astounded to learn that one could be an astrophysicist for a living, only to be deterred by her father, who believed the best career was as a doctor or lawyer.

Seager graduated with a BSc in the Math and Physics Specialist Program at the University of Toronto. Like Hogg, she did graduate work at Harvard where her realization of the surprising diversity of exoplanets has led to Seager’s maxim, “For exoplanets, anything is possible under the laws of physics and chemistry.”

Enjoy the Leap Day While You Can

Today, February 29th 2020, is a leap day with an extra 24 hours added to the calendar. The extra day is added to keep our calendar aligned with the seasons. The need for a Leap Day is a result of the physics with the Earth rotating on its axis while simultaneously revolving around the Sun. Physics also explains why the need for leap years will eventually disappear!

Image Credit: timeanddate.com

Our calendar year is designed to match the seasons, which occur because of the axial tilt of the Earth. At the June solstice, the northern hemisphere is tilted towards the sun but it is tilted away from the Sun at the December solstice. Neither hemisphere is tilted towards or away from the Sun at the equinoxes.

Solar Day vs Sidereal Day
The Solar Day vs Sidereal Day
Image credit: www.solarsystemscope.com/

But the Earth is also simultaneously spinning on its own axis, with a period of 24 hours that make up our cycle of days and nights. The 24-hour solar day is the time it takes between successive “noons” – the time when the Sun reaches its highest point in the sky as seen from Earth. The solar day is about 4 minutes longer than the time the Earth to rotate by 360 degrees (called the sidereal day) because the Earth is moving around Sun during each day.

The calendar was originally intended to start at the Spring Equinox with a calendar year measuring the time it takes for the Earth to revolve around the Sun and make it to the next Spring Equinox.

The calendar year is the period of our orbit around the Sun but it does not match up with the whole number of 365 solar days – it takes a bit of an extra day for the Earth to get back to the same position with respect to the Sun.

The calendar year is 365.24219 solar days.

Image Credit: www.ctvnews.ca

The extra 0.24219 days is close to 0.25 or ¼ of a day so adding an extra day every 4 years keeps the seasons and the calendar synchronized. It is a bit more complicated because the extra 0.24219 is not exactly ¼ and the Gregorian Calendar accounts for this with its leap year rule:

A year is a leap year if it is evenly divisible by four,
but years that are divisible by 100 are not leap years,
unless they are also divisible by 400.

For example, 2020 is a leap year, the years 1700, 1800, and 1900 are not leap years, but the years 1600 and 2000 are.

In the long term, changes in the Earth’s rotation rate need to be taken into account. The Earth’s rotation rate is slowing down, mostly due to the tidal forces and friction between the Earth and Moon. The day gets about 1.4 milliseconds, or 1.4 thousandths of a second, longer roughly every 100 years. A leap second is occasionally applied to accommodate for this slowdown in the Earth’s rotation and other irregularities. If you can wait around for about another four million years then the day will have lengthen by about 56 seconds. That is enough so that a calendar year will have exactly 365 solar days and we won’t need a leap year!

So enjoy the leap day while you can and a Happy Birthday any leaplings born on Feb 29th.

Celebrate 40+ Years of the Canada-France-Hawaii Telescope

Canada-France-Hawaii Telesocpe located atop the summit of Mauna Kea, Hawaii

Come celebrate 40+ years of operations at the Canada-France-Hawaii Telescope (CFHT) at our Paul Sykes Memorial Lecture. 2019 marked the 40th anniversary of the Canada-France-Hawaii Telescope. Hear stories of the science, staff, and their adventures over those 40 years along with plans for the future.

Speaker: Mary Beth Laychak, CFHT Director of Strategic Communications
Title: 40 Years of Astronomy at the Top of the World

When: Friday, February 21, 2020 from 7:30 PM to 9:30 PM
Where: Saywell Hall, Room SWH10081, SFU Burnaby Campus

The event is free and open to the public! Our meetup event has additional details, directions, and a map.

Framed CFHT posters will be available for sale as special merchandise. The posters are from Dynamic Structures, a BC company located in Port Coquitlam, who did important engineering work in constructing the CFH telescope and enclosure – find out more at the RASC 2020 General Assembly in June where David Halliday, president of Dynamic Structures, is one the speakers.

Mary Beth Laychak, Director of Strategic Communications at the CFHT.
Mary Beth Laychak is the Director of Strategic Communications at the CFHT

Mary Beth has an undergraduate degree in astronomy and astrophysics from Penn State University and a masters degree in educational technology from San Diego State. Her passions include astronomy, sharing astronomy with the public, astronomy based crafts, and running.

The Canada-France-Hawaii Telescope is a joint facility of the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The 3.6m telescope is located on the summit ridge of Mauna Kea, a 4200 meter, dormant volcano on the Big Island of Hawaii.

Inside the CFHT Observatory Enclosure. Image credit: National Research Council of Canada

CFHT crucially supported seminal observations:

  • The discovery of Dark Energy,
  • The first detections of cosmic gravitational lenses that paved the way to mapping dark matter across the universe, and
  • Tracking the first interstellar asteroid (Oumuamua) as it sped through our solar system

The CFHT remains at the forefront of astronomy thanks to the quality of its site, its state-of-the-art instrumentation, and the dedication of its staff. CFHT’s annual publications rate now exceeds 200 papers per year and has never been higher. The same can be said for CFHT’s #2 worldwide ranking for overall “science impact” in astronomy

The Annual Paul Skyes Memorial Lectures

These lectures honour Paul Sykes. Paul actively pursued his interest in astronomy, attending conferences and joining RASC, where he became a Life Member. Paul Sykes passed away in October 2005 at the age of 87 and left the Vancouver Centre a generous gift.

Paul Sykes was born in Hummelston, Pennsylvania USA in 1918. He acquired his interest in astronomy at an early age. During his teens he published his own monthly astronomical column and gave at least one lecture.

He was an officer in the United States Air Force, served in the Pacific during WWII attaining the rank of Captain. He was awarded a Presidential Unit Citation, the U.S. Air Medal, the Oak Leaf and Cluster and the Bronze Star. Following the war he attended UBC earning a degree in Physics in 1948. He rejoined the United States Air Force and attended the Oak Ridge School of Reactor Technology, studying nuclear physics. He worked on the NERVA Project, a nuclear rocket development effort and rose to the rank of Major.

Paul was appointed a lecturer and administrator in Physics at UBC and remained there until retirement in 1983.

Two Women’s Contributions to Measuring Distances

Today is an appropriate day to celebrate the significant discoveries of Henrietta Swan Leavitt and Sandra Faber in measuring distances in the Universe as Feb 11th is recognized by the United Nations as its International Day of Women and Girls in Science.

Many amateur astronomers know of the significance of Henrietta Swan Leavitt’s discovery of the period-luminosity relationship in Cepheid Variable stars; the longer the period of a Cepheid, the more luminous it is. Edwin Hubble used this relationship with his observations of Cepheid Variable stars in the Andromeda Galaxy (M31) to estimate that the Andromeda Galaxy lies at a distance of 1.5 million light-years; thus resolving the Great Debate with Harlow Shapley conceding that spiral “nebulae” (what we now call galaxies) are located outside our milky way.

Plot prepared by Leavitt in 1912. Period on the x-axis and brightness on the y- axis for 25 Cepheids in the Small Magellanic Cloud (SMC). The relation also holds for luminosity because all stars in the SMC are at about the same distance from Earth.

The luminosity of a star is the total amount of light it emits from its surface. On the other hand, how bright a star appears depends on its luminosity and its distance from the observer because the light spreads out over a greater surface area, in accordance with the inverse square law.

Leavitt’s work was critical because once the luminosity is known, the brightness  from Earth can be measured and the distance estimated from the inverse square law.

Image Credit: Australian Telescope National Facility – CSIRO

Later in the 1970s, Sandra Faber found another luminosity relationship. Faber was following up on some of her thesis work that looked at absorption lines — those of calcium, sodium, or magnesium in the visible portion of a galaxy’s spectrum — when she spotted some evidence this relationship.

“Well, as I was taking the data, I could not help but notice that the more luminous galaxies had broader lines.” 

Sandra Faber interview in 2019

Further data analysis revealed a pretty good empirical relation between the luminosity and the velocity dispersion of stars near the centre of elliptical galaxies. This relationship became known as the Faber-Jackson relation after the work was published in a paper authored by Faber and Robert Jackson, her research assistant at the time. For any visible elliptical galaxy, the velocity dispersion can be measured from the width of the absorption lines and its luminosity estimated using the Faber-Jackson relation. The distance to the galaxy can then be calculated using the inverse-square law applied to its luminosity and its observed brightness from Earth.

Velocity dispersion (y-axis) plotted against absolute magnitude (x-axis) for a sample of elliptical galaxies, with the Faber–Jackson relation shown in blue. Image Credit: Wikipedia

Faber refined these methods as the head of a group, known as the Seven Samurai, on a project to measure distances and velocities of a sample of elliptical galaxies. The project failed to validate its original hypotheses on more accurate versions of the Faber-Jackson relationship but it did establish distances to 400 galaxies. Using these distances, they made a map of ellipticals around us and noticed that the recessional speeds were not exactly as predicted from a simple uniform Hubble law (due to the expansion of the Universe). Faber recalled, David Burnstein, one of he seven samurai remarking

“Look at this. There’s a whole region in Centaurus, and it’s moving at 1000 kilometres a second”

Dave Burstein remark, recollection by Faber in 2019,

Instead, large patches of the Universe were moving away from us too quickly or too slowly! This work culminated at a small meeting of cosmological experts in Hawaii in January 1986. The samurai sliced up the standard theories of the time, by announcing that the universe was expanding lopsidedly. A vast region of space 500 million light-years in diameter, containing hundreds of thousands of galaxies, was being drawn toward a huge concentration of mass later dubbed the Great Attractor. One attendee at the meeting said “In 20 years of science reporting, I have never seen such pandemonium at a scientific meeting”.

Faber has done significant research in other areas and has been recognized with numerous awards. Earlier this year in Jan 2020, the Royal Astronomical Society awarded her its Gold Medal in Astronomy. The award recognizes Faber “for her outstanding research on the formation, structure and evolution of galaxies, and for her contributions to the optical design of the Keck Telescopes and other novel astronomical instruments.”

2019 Nobel Prize Awarded to Canadian-born James Peebles

I was feeling a bit guilty not knowing much about James Peebles’ work and the discoveries that led him being awarded 1/2 of the 2019 Nobel Prize in physics. After all, he was born in St. Boniface, Manitoba (now part of Winnipeg) and obtained his undergraduate degree at the University of Manitoba (my Alma Matter). Peebles was awarded the prize for contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos. Peebles is a theoretical cosmologist whose work involves the study of the largest-scale structures and dynamics of the universe with fundamental questions about its origin, structure, evolution, and ultimate fate.

Fortunately, Dr. Joanna Woo presented a great summary of his work at Simon Fraser University’s celebration of the 2019 Nobel prizes at Science World last Wednesday. Dr. Woo is an astrophysicist who has recently joined the faculty at SFU. She is also the new Director of the Trottier Observatory. Her presentation, that described how Peebles’ theoretical work made predictions confirmed by three Nobel prize worthy observational discoveries, really highlighted the significance of Peebles’ theoretical research. The next three sections are my short summary.

Cosmic Microwave Background (CMB) Radiation

Peebles and his colleges developed theoretical models that started at the big bang and ran the clock forward to predict the temperature that the initial background radiation would have cooled to, predicting a present temperature of around 10° K. Penzias and Wilson from Bell labs won the 1978 Nobel Prize for their detection of the CMB at a temperature of about 3.5° K. Although both groups published their results in same issue of Astrophysical Journal Letters, only Penzias and Wilson received the Nobel Prize for the discovery of the CMB.

Fluctuations in the CMB

Peebles realized that the young universe must have had fluctuations in density in order for galaxies, stars, and planets to form. His theoretical models predicted the impact that these fluctuations had on the cosmic microwave background. These predictions were confirmed, with the help of the NASA COBE mission in 1989, with the discovery and measurement of small variations in the CMB temperature in different directions. John C. Mather and George F. Smoot were awarded the 2006 Nobel Prize for these discoveries that confirmed Peebles’ theory

Proportions of Matter, Dark Matter, and Dark Energy in the Univese

Peebles contributed to reviving Einstein’s cosmological constant, which has been renamed to Dark Energy, in models that predicted the composition of the Universe to be 5% ordinary matter, 26% Dark Matter, and 69% Dark Energy. Dark energy remained just a theory for years, until the universe’s accelerating expansion was discovered in 1998, resulting in the 2011 Nobel Prize for Saul Perlmutter, Brian Schmidt and Adam Riess. More recent studies, such as NASA’s Wilkinson Microwave Anistropy Probe and Europe’s Planck spacecraft have refined the proportions and led David Spergel, a cosmologist who worked on these missions, to remark “Jim Peebles is right”!

Other Half of the 2019 Nobel Prize in Physics

The other 1/2 of the 2019 Nobel went to Michel Mayor and Didier Queloz for the discovery of the first exoplanet orbiting a solar-type star. They discovered the exoplanet 51 Pegasi b using the radial velocity method.  This method, also known as Doppler spectroscopy, measures a star’s wobble velocity which can be evidence for an orbiting planet. Another Canadian connection here is that the radial velocity method was pioneered by G. Walker, B. Campbell and S. Yang from the University of British Columbia. The star 51 Pegasi is a solar-like star but the exoplanet is not Earth-like. It is more like a small Jupiter that orbits its star about every four days and is much closer to its star than Mercury is to the Sun

More Noble Prize Celebrations

Simon Fraser University celebrates the newly awarded Nobel Prize winners in chemistry, physics and medicine/physiology each year. This year’s celebration included two more talks from SFU faculty:

  • “The Energy Revolution” by Dr. Stephen Campbell, doctorate in semiconductor electrochemistry, CTO at Nano One
  • “Controlling the burn – how life senses adapt to changes in oxygen availability” by Dr. David Vocadlo, Canada Research Chair in Chemical Biology, Department of Chemistry

Looking forward to next year’s celebration.

Volunteer with RASC Vancouver in 2020

Aldergrove Meteor Watch Event Photo
RASC Vancouver at the Aldergrove Park Meteor Watch

Why not make a resolution to volunteer with RASC Vancouver in 2020? There are RASC events scheduled throughout the year, and all over the Lower Mainland, that need volunteers. And this year, we need additional volunteers for the RASC 2020 General Assembly we are hosting June 5-7.

Expertise in astronomy is not required, we would be happy to have you help in any capacity. Make a on-line request to join our volunteers email list or contact our events coordinator, Hayley Miller, either at a members’ monthly meeting, or via an email to [email protected]  

Note that You must be a member in good standing to volunteer at a public RASC event due to liability and insurance concerns.

For me, the satisfaction in volunteering comes from the joy in hearing “Wow” when someone looks through my scope to see the Moon’s craters or Saturn’s rings for the first time at a RASC Star Party, the connections made when handing out a SkyNews magazine or Star Finder to someone who comments that they love he night sky, and the sense of community developed in working with other RASC volunteers to educate and inspire awe of the Universe.

You can contribute in many ways. RASC Volunteers have taken on tasks like the following:

  • Spending a few hours handing out star finders or other RASC Literature
  • Chatting with guests at our events about anything astronomy related
  • Welcoming guests and directing them to activities at our Astronomy Day event
  • Giving an educational talk or workshop at a library, to a scouts or guides group, or at a school
  • Arranging travel and logistics for speakers at our Monthly Meetings
  • Leading hands-on astronomy activities at an event
  • Doing public relations or helping with our social media
  • Bringing a telescope to a public star party to let the public have a look at what is up in the sky
  • Writing an article for our NOVA newsletter or our website
  • Advocating for Light Pollution Abatement with local governments
  • Organizing and running an event in your community

Don’t forget that there are other volunteer opportunities at the RASC 2020 General Assembly (and a gentle reminder that early-bird pricing for GA registrations ends in a couple of weeks on Feb 15th).

Help with Pacific Northwest First Nations Astronomy

You can find your way around the indigenous constellations with a new planisphere available from the RASC e-store. It includes constellation wheels that show Ojibwe, D(L)akota, and Cree star maps. A separate constellation guidebook, with the Ojibwe constellations is also available. These are great but the Ojibwe, D(L)akota, and Cree territories are located in the prairies and eastern Canada rather than out here on the west coast of BC.

RASC Vancouver would like to learn more about the sky lore, constellations, and astronomical knowledge of the First Nation peoples of the Pacific Northwest to show off at the RASC 2020 General Assembly on June 5th-7th 2020. What were their sky stories? Did they see and name patterns of stars similar to Western constellations?

Little information on the astronomical knowledge of Pacific Northwest First Nation peoples is available. If you know anything, have contact with anyone knowledgeable about this or would just like to help with some research then please send us an email to [email protected] -vancouver.com.

The Coastal Salish are a cultural group that inhabit the land around Metro Vancouver, extending down to into Washington, and north of Comox on Vancouver Island.

Coast Salish Territories
Image Credit: University of Victoria Legacy Art Galleries

Other linguistic and cultural groups including the Haida, Tsimshian, Nuxalk (Bella Coola), Northern Wakashan, Kwakwakw’wakw (Kwakuitl), and Nuu-chah-nulth (Nootka) reside further north along the Pacific Northwest coast.

Living around the Salish Sea and next to the Pacific Ocean, one would think these peoples would be sea-faring folk that navigated using the stars. The mild climate and abundant natural resources made possible the rise of a complex culture – they had time and energy to devote to the development of fine arts and crafts and to religious and social ceremonies – but what about astronomy?

Several First Nations peoples have sky lore related to “the Big Dipper”. The Mi’kmaq, who lived in southeast Canada, saw the Big Dipper handle stars as hunters chasing a Celestial Bear. The Iroquois had a similar legend. The Ntlakyapamuk, or Thompson peoples in the southern British Columbia Interior also saw three hunters but they were chasing a grizzly bear. It is interesting that the Ancient Greeks also saw a Great Bear, Ursa Major, in this pattern of stars.

Three brothers Chase the Celestial Bear
Image Credit: McMaster University

Other First Nations peoples in BC had different sky lore for the Big Dipper.

diving loons as seen by the Klamath peoples (in the British Columbia plateau region). To the Tahltan peoples in northwestern British Columbia, the stars of the Big Dipper were the Grandfather Stars. Grandfather Stars told the Thaltan people that as long as he continued to go around the northern sky, everything would be well.

Frank Dempsey, Aboriginal Canadian Sky Lore of the Big Dipper,
JRASC April / avril 2008 Volume/volume 102 Number/numéro 2

Are you a Stellarium user? If so then you can change the sky culture to something other than the default Western culture.

Screenshot Chnage Sky Culture in Stellarium
Changing the Sky Culture in Stellarium

such as the colourful Ojibwe sky culture.

Ojibwe Sky Culture in Stellarium
Stellarium with Ojibwe Sky Culture

A Recap of Some Exoplanet News

Here is a recap of some Exoplanets news that came to my attention last week – four science stories and one music video.

Orbits of all three known planets in the TOI 700 system. 
Image credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA)

First, NASA announced that Tess, the Transiting Exoplanet Survey Satellite, has discovered its first Earth-size planet in its star’s habitable zone. TOI 700 d orbits a red dwarf star that is relatively quiet – no flares were detected in 11 months of TESS data. The star is located just over 100 light-years away in the southern constellation Dorado. It has about 40% of the Sun’s mass and size and about half its surface temperature. Three planets have been detected but only the outermost is in the habitable zone where water can remain liquid on its surface.

Anna Hughes, a PhD candidate at UBC, spoke at the January RASC Vancouver monthly meeting about Magnetic Fields Around Dwarf Stars. Some types of magnetic fields are associated with active stars that can throw bursts of radiation and charged particles at orbiting planets, potentially sterilizing them. She explained her work in studying magnetic fields around ultra-cool dwarf stars and their impact on the potential habitability of surrounding exoplanets. Ultra-cool dwarfs were not expected to have magnetic fields because they are completely convective, without the shearing between different layers that generates magnetic fields in larger stars. Using large arrays of radio telescopes, Hughes studied several ultra-cool dwarf stars where the presence of magnetic fields has recently been detected. One of the system she studied was Trappist-1, a system with seven confirmed exoplanets, three of which are in the habitable zone.

Cool fact: ultra-cool dwarf stars have not yet experienced death. Their lifetimes are expected to exceed several hundred billion years which is longer than age of the universe.

A high-school student discovered a new exoplanet three days after starting his internship at NASA. NASA confirmed the work of Wolf Cukier, that was submitting in a paper announcing the discovery of TOI 1338 b at the 235th American Astronomical Society meeting. It is a binary system and Cukier saw a signal that that was first thought to be a stellar eclipse. Instead, it turned out to be a planet orbiting two stars.

Artash Nath, a Grade 8 Student from Toronto, posted a message to the RASC mail list about his project with a free module using Python and a Jupyter Notebook that allows anyone to get started with machine learning on a dataset of transit light curves to predict the exoplanet planet-star radius ratio. An online tutorial is available from his Github account www.github.com/Artash-N.

On a lighter note, a older video on exoplanets created by Montrealer, Tim Blais from A Capella Science, got my attention by fitting “Pegasi 51-b” and “Spectral Class G” into the rhyme and rhythm of his “Whole New Worlds” video.

Plate Solving 2 – Automated Alignment

The Plate Solving 1 article described how Plate Solving software uses pattern matching to determine the stars and other objects that appear in an image. Plate Solving provides additional benefits when used with a computer connected mount – including accurate gotos with automated alignment.

The usual setup routine for using a goto mount is to first roughly polar align mount so that the mount’s polar axis is pointing at true north. This is often done with a small polar scope attached on the mount. An alignment process with the following steps is then repeated on several stars:

  • Select an alignment star that is visible from a list provided by the mount
  • Slew to the selected star
  • Use the hand-controller to center the selected star in the finder and eyepiece.

Plate solving can automate the alignment process. It requires a computer that controls the mount’s movements and can take images through the scope or finderscope. Many astronomy apps such as Stellarium, Carte du Ceil, or KStars are capable controlling a variety of mounts from vendors such as Celestron, Meade, iOptron, or Skywatcher. The process starts by selecting a target star or object in the App – then the computer takes over:

  • The computer tells the mount to slew to the target.
  • An image is taken through the scope and downloaded to the computer.
  • The computer uses Plate Solving to determine that region of the sky that the scope is actually pointing to.
  • The computer issues a sync command to update the mount’s alignment model to where the scope is pointing.
  • If the scope is not pointing at the target then the computer again tells the mount to slew to the target and the above steps are repeated

I automate alignment with my Celestron CGEM mount, Edge HD 8 scope, and a small Raspberry PI computer. The computer controls the mount and is also connected to a ZWO ASI178 camera on a piggy-backed 60 mm ZWO guidescope. The Raspberry PI is velcro’d to the mount and runs the Stellarmate OS but I connect to it remotely from a Macbook laptop running the KStars astronomy app over a wireless connection.

KStars displays a map of the sky for my location and time. I normally start by selecting a bright star relatively close to Polaris – making sure to pick one that is above 45 degrees in the North or North-East to avoid being block by the hedges or house in my front-yard. I then using KStars to have the mount “goto” to the target – in the image below my target was the bright star Mirfak in Perseus.

Screenshot of Kstars goto with Celestron CGEM mount.
Initial Goto the star Mirfak with KStars connected to a Celestron CGEM Mount

The EKOS alignment module in KStars handles the automated alignment procedure and plate solving.

EKOS Alignment Module Screenshot
Plate Solving Settings for EKOS Alignment Module

The main settings that I use are are highlighted with orange oval boxes in the screenshot above.

  • Select the “Slew to target” radio button to repeat a slew to the target if, after plate solving, the scope is not actually pointing at the target.
  • Set the Scope selection to “Guidescope” because I do automated alignment and plate solving using my guidescope.
  • Select “ZWO ASI178” in the CCD drop-down as that is the camera I have attached to the guidescope.
  • Set “Exp: 2 sec” to use a short 2 seconds exposure time. I occasionally increase this if not enough stars are visible.
  • Set “Bin: 4×4” so binning is used to combine pixels and decrease the size of the images.

Then I just click the “Capture and Solve” button. After an image is taken and plate solving is done, the image and results of plate solving, including the RA (right ascension) and Dec (declination), is displayed on the left hand side. On this night, plate solving succeeded despite the presence of the significant cloud cover seen in the image.

EKOS Screenshot after Successful Plate Solve and Alignment
EKOS Screenshot after Successful Plate Solve and Alignment

I use automated plate solving with my guidescope when doing visual observing – it turns my guidescope into an automated electronic finderscope that is faster and more accurate than doing a manual alignment.

When imaging, I extend the procedure to do plate solving with my primary scope and a Nikon DSLR camera. One great feature in KStars is that it shows the camera FOV on the sky map with its rotation after plate solving. That makes is easier to rotate the camera and compose the image so that it includes additional interesting objects.

Screenshot of Kstars with FOV plus rotation after Plate Solving
Field of View plus Rotation shown in KStars

Try it out – for technolophiles, doing automated alignment with plate solving with inexpensive hardware and free software is pretty cool stuff.