Part of the fun of amateur astronomy is getting caught up in “rabbit holes”. You see something on Facebook, that gets you looking up articles in the popular press, and then into academic publications, and they lead you in a different direction and everything is so fascinating and time just rushes by…
The Moon aligned with Ogden Point breakwater – Randy Enkin photo
My current example is looking into the timing of craters on the moon – when they enter and exit the umbra or full shade of the Earth. It was an important way to figure out the time, and therefore one’s longitude, before reliable clocks were made. In the 18th century, astronomers recognized that there is a problem (La Hire, Tabulae Astronomicae, Paris 1707); the earth’s shadow is over 100 km bigger than expected. The anomaly is bigger than can be explained easily with the atmosphere. One would think this is a simple geometric problem that is fully understood, but it is still under study!
Amateur astronomers are helping collect the necessary data. Sky and Telescope publishes predicted times for when the shadow is expected to cross 24 prominent craters, and they request people to email in their observed times. Upcoming May 26, 2021, eclipse online info. Up to 2011, their database includes 22,539 observations by 764 different people. If the sky is clear between 02:52 and 05:48 on Wednesday May 26, I hope to add my name to the list!
The point is, we are a community of interesting and interested people. We set challenges for ourselves. Some are simple; some are very difficult. Get your telescope to track better. Process an image to show more detail. Understand black holes a bit more. Learn another myth of a constellation. And then we get together (virtually, these days) and support each other in these pursuits.
VIdeo frame of ISS taken through an 8″ Dobsonian by Nathan
ISS photo – Nathan Hellner-Mestelman
Used a iPhone mount using a 30-min video slow motion through a 5mm eyepiece, 2.5x Barlow and 8″ Dob (1,200mm f/l), so about 600x magnification, 2-3 arc secs
Astronomy Day on May 15th – Randy Enkin & Lauri Roche
We were so fortunate to have a clear sky for this online event
Reviewed all the presenters and thanked everyone
Spectroscopy – Tom Field
Intro by David Lee
70-80% of astronomical research is done with spectroscopy
Rspec-Astro.com – spectroscopy software for amateur astronomers
Bunsen invented his burner to burn elements to see their component spectra
Emission and absorption lines in spectrum
“The Computers” Annie Jump Cannon – they created categories for spectral plate analysis
Equipment to use for capturing spectrum
Star Analyser Grating – US$195
Other adapters and gear available
A slit instead of a grating, which yields more resolution, but costs more and requires better technique
Compared spectra of 8 different stars – Torsten Hansen
Doing science
Graph the results
Spectroscopy is more immune to light pollution than traditional astrophotography, so urban observing works
Wolf-Rayet stars (WR140) – shows this late-stage star with carbon-rich spectra
Spectra can be measured of: planets, comets, meteors, the Sun, Supernova, stars
Measuring Doppler Shift, or is it red/blue shift?
Extended objects like nebulae need a slit instead of a grating
Black Hole? no, but the accretion disk emits light
Calculating red shift
Spectroscopy can reinforce other observational skills
Distance between sensor and grating needs to be precisely setup
Emission versus absorption lines
Can use other grating, since RSpec can calibrate to other grating resolutions. RSpec grating uses 100 lines/mm which is easy to use, and yields brighter spectra.
Calibrate on a known star, then study other objects
Notices
There is no Astro Cafe next Monday due to the Victoria Day holiday. The next Astro Cafe is scheduled for May 31st.
If anyone would like to lead a citizen science group, please contact David Lee
A celebration of International Astronomy Day in Victoria, BC, Canada was held on May 15, 2021 as a virtual online event, sponsored by the Friends of the DAO and RASC Victoria Centre. Hundreds of people attended this live-streamed 4-hour event through both Zoom and Youtube.
Live Solar Viewing from the DAO with David Lee, Sid Sidhu & Chris Purse
Guest Presentation – “Fossils in our Galaxy” by Dr. Kim Venn, a specialist at UVic in observational stellar spectroscopy, and the chemo-dynamical analysis of stars in the Galaxy and its nearby dwarf satellites. Stars contain a fossil record of the chemistry of the Universe at the time and place where they were born. Stars formed early in the universe contain very low amounts of elements heavier than Helium, and astronomers call these stars ‘metal-poor’. They are the fossils of ancient star formation in the galaxy. By studying the most metal-poor of these stars, we can read that fossil record to learn about the origin of the elements and formation of the Galaxy. Dr. Venn discussed the recent results on the metal-poor galaxy, including newly discovered streams in the halo, very metal-poor stars found in the Galactic Centre, and metal-poor stars in the Galactic disk that orbit in the opposite direction.
University of Victoria Telescope Tour with Karun Thanjavur
Ask an Astronomer (or two) with Jason Beaman and Nathan Hellner-Mestelman, hosted by Amy Archer
Astrophotography Gallery with Marjie Welchframe, David Lee and friends featuring music from Vox Humana, Jeff Enns (composer)
Planetaruim Show from the CU – Draco & Hercules – Aaron Bannister & the constellation blanket
Live Stream from the Plaskett Telescope, the Centre of the Universe (CU) and other locations featuring David Lee, Dan Posey, Dave Payne, and Brock Johnston – the RASC Electronic Assisted Astronomy Group and hosted by Ruhee Janmohamed
