Our Night Sky

As I mentioned on the main The Great Courses page, I like this show pretty well, and would recommend it as a good introduction to the stargazing and amateur astronomy. Luckily this, pretty good, course is available on both Kanopy and Hoopla from my library, so it's pretty easy to watch on you computer, iOS device, and probably Roku and other platforms.

Our Night Sky - Professor Edward M. Murphy, Ph.D. - University of Virginia

This is the general description of the course/series.

For thousands of years, the star-filled sky has been a source of wonder, discovery, entertainment, and instruction. Ancient people from nearly every continent and culture wove exciting stories about the mythological figures they saw in the heavens. People also used the sun, moon, and stars for time-keeping and navigation. And careful observers throughout Europe, the Middle East, Asia, and elsewhere kept precise astronomical records, eventually paving the way for the Scientific Revolution and its remarkable discoveries about the nature of the universe.

Episode 1 The Constellations and Their Stars

This episode is really just laying out the syllabus for the course, an true overview. He then discusses, in broad terms, the origins of Constellations, and the difference between a constellation (a pattern of stars in the sky, like Ursa Major) and an asterism (the Big Dipper). He then tells us about Ptolemy’s 48 classical constellations, and the Almagest (his book and star catalog of 1,028 stars, Arabic for “the greatest” from 150 AD). Of course Ptolemy saw a geocentric theory of the universe, with the Earth in the center which dominated for 1,400 years.

Next he tells us about the Greek astronomer Eudoxus (390-340BC) and how he learned about the constellations from the Egyptians before writing his Enoptron (Murrow) and Phenomena (appearances), which was later referenced by Aratus (315-245 BC) - as the original was lost to history. Next, the tells us because there were no constellations created within 36 degrees of the south celestial pole, the developers must have lived at about 36 degrees of latitude. This is south of the Greek mainland and north of the Egyptian mainland. He uses this to deduce that the original Samaritan and Babylonian cultures developed the Zodiac and the constellations.

Next he tells us about other star catalogs, and brightness and color, with blue stars being comparatively hotter than red/orange stars. The are classed by letters O-30K/B-20K/A-10K/F-7K/G-6K/K-4K/M-3K (Oh Be a Fine Girl, KISS Me). Each of these class have 0-9 sub classes.

He closes with distances, introducing the astronomical unit (AU), the distance of the Earth from the Sun, 1AU (150M km) and light years (5.88 trillion miles). He tells us that Voyager 1 is 19 light hours away (in 2019). Alpha Centauri, the nearest star system to us, is 4.4 light years away. Finally he tells us about sky charts and planispheres.

Begin your study of the night sky by investigating the origin of the constellations—the traditional groupings of stars that mostly date to antiquity. The well-known constellation Orion illustrates the fascinating mix of beauty, mythology, and scientific knowledge to be found wherever you look in the heavens.

Episode 2 Seeing and Navigating the Sky

This episode is another good overview, starting with what twilight means. During Civil Twilight (right after sunset), we’re told you can still read outside without artificial lighting and only the brightest stars and planets are visible. Next is nautical twilight you can see most of the celestial objects needed for navigation, but you can still see the horizon to take their altitudes. Finally is Astronomical twilight, where there is not enough light to see the horizon clearly, and the sun no longer illuminates the sky and the faintest objects are visible. Then he explains that twilight lasts longer the higher your latitude. For example, at the equator astronomical twilight ends 1 hour and 12 minutes after sunset, at higher latitudes it can last over 2 hours. We’re told that if you live in a dark sky area you can see up to 6,000 stars are bright enough to be send at night, but only about 1/2 are above the horizon. Next light pollution is explained as stray light leaking into space, and wasting energy not illuminating what we intended to see, and what a ‘full-cutoff’ light fixture is. Then we learn about night vision adaptation and red flashlights, and averted vision.

Next we move on to start brightness, including apparent brightness and actual energy output (luminosity). Then we’re introduced to the inverse square law, and how light intensity drops off as the square of the distance away. The magnitude scale is then described, as defined by Hipparchus in the 2nd century BC - the brightest stars were first magnitude, and the faintest he could see were 6th magnitude. The magnitude system has been redefined so that a difference in 5 magnitude is exactly 100 times in brightness. A 1 magnitude difference is about 2.5 times, 2 magnitudes is 6x and 3 is 16x. Polaris is a 2.0, the naked eye limit is 6, binoculars are 10, and an 8” telescope in dark skies can do 14. Limiting magnitude is the dimmest star magnitude that you can see in your typical skies. A good dark sky site can see as low as magnitude 6, a typical urban site can only do as dim as magnitude 4. A city area might be as high as 3, with only about 50 stars visible.

Next we learn about sky distances and the “celestial sphere”. We learn that we can estimate distances with our hands, with a finger being about 1 degree at arms length, fist being about 10 degrees, and your outstretched thumb-to-oustreteched pinky is about 20 degrees. The sun and moon are about 1/2 degree across, and the belt in Orion is about 3 degrees, and Rigel to Betelgeuse is about 18.5 degrees. Most people can only see about 1 arc minute resolution in the sky, and 1 arc second is about the size of a quarter at a distance of 3.1 miles away. Zenith is directly overhead.

The naked eye is a powerful instrument—if you know how to use it. Learn the best times and conditions for observing, how to identify the positions and magnitudes of stars and planets, how the sky changes over the course of a night, how to use astronomical maps such as a planisphere, and more.

Episode 3 Using Binoculars and Backyard Telescopes

This episode was fine, and I would watch it (and did) as part of the series, but not quite as interesting as Episode 2.

here are many choices when selecting binoculars or a telescope. Learn what to look for in light-gathering power, optical design, magnification, mounts, and other features. Professor Murphy also suggests several tips for getting the best observing experience out of your equipment.

Episode 4 Observing the Moon and the Sun

I always find the pyramids interesting, and this was no exception. I was interested in his take on the shafts pointing to the stars since I'd read a book on this previously, and was surprised to find that these shafts were not as regular as I had imagined and that one could not actually site the stars from inside of the tomb as I had previously believed.

Charting the motions and changes of the sun and moon may be humankind's oldest astronomical activity. Discover how both objects offer rich opportunities for study. Also learn the precautions to take when observing the sun, which is the only star that can be seen up close and in detail.

Episode 5 Observing the Planets with a Telescope

Similar to the pyramids, I've always had a fasciantion with the Anasazi, and was disappointed to hear that the sun-dagger had been damaged by tourism. It's still a place that is on my bucket list to see if I ever get the chance.

The rings of Saturn, the bands of Jupiter, the phases of Venus, the polar caps of Mars—these and other planetary features are visible through a small telescope. Learn when viewing opportunities arise for each of the planets and what sights await the dedicated observer." and…

Episode 6 Meteor Showers, Comets, Eclipses, and More

Interesting, but to me, not as interesting as some of the other episodes.

Explore a variety of special phenomena that are among the wonders of the sky. Some, like bright meteors, aurora, and many comets, are largely unpredictable. Others, like eclipses and annual meteor showers, occur at well-known times—although it may require a special trip to see them.

Episode 7 The Northern Sky and the North Celestial Pole

An above-average episode for me, as I was unaware that primitive man used the iron from meteors to prior to developing the technology to actual produce iron.

Embarking on the second half of the course in which you systematically tour the entire sky, study two constellations that are continuously in view from the Northern Hemisphere: Ursa Major and Cassiopeia. Also explore the slowly shifting position of true north in the sky.

Episode 8 The Fall Sky

Again, interesting, but not as much as some of the others. It's really hard to image seeing an eclipse or comet and not know what it was, but on some level I can accept that if you didn't know it would be frightening.

Navigate your way around the autumn sky from the Northern Hemisphere, discovering how the classical myth of Andromeda ties together the stories of the nearby constellations of Cassiopeia, Perseus, Cepheus, Pegasus, and Cetus. The sights include the Andromeda galaxy, the nearest large galaxy to our own.

Episode 9 The Winter Sky

Another pretty good episode, partly just because I appreciate it that not all men of science immediately discount anything of faith or in the Bible. Much like in Cosmos, there are excellent descriptions of the faithful aiding our understanding of the stars.

Continuing your focus on the constellations of the Northern Hemisphere, survey the magnificent winter sky, dominated by Orion. "Star hop" around the region, which includes a wealth of interesting stars, globular clusters, nebulae, and other features, especially the Orion Nebula—the finest nebula in the northern sky—and the Pleiades and Hyades star clusters in Taurus.

Episode 10 The Spring Sky

Pretty good, but constellation history is covered everywhere, so a lot of this wasn't really new to me.

The spring sky opens the view into intergalactic space perpendicular to the plane of the Milky Way. Among the objects visible are the immensely rich galaxy clusters in Virgo and Coma Berenices, which are many millions of light-years distant and can be seen with small and moderate telescopes.

Episode 11 The Summer Sky

Pretty good, but again, like Episode 10, much of this is covered elsewhere so it feels less valuable, though it's exclusion would also seem strange. Worth watching.

Arching high overhead in the summer sky is the Milky Way, which is the plane of our galaxy seen from the inside. Tour this densely packed region of stars of all types, from dusty regions of star birth to the exquisite shells of dying stars. Here, a useful orienting feature is the Summer Triangle.

Episode 12 The Southern Sky and the Milky Way

Astrology. What more is there to say? It is historically important, and it's interesting that they don't deal with precession, but otherwise? Meh.

In this final lecture, travel to the Southern Hemisphere for sky views inaccessible from northern latitudes. Discover the famous Southern Cross, the Large and Small Magellanic Clouds, and a spectacular panorama of the Milky Way—along with new myths and stories that add a human dimension to our marvelous night sky.