Lunar Maria

António Cidadão, of Oeiras, Portugal, many years ago produced a wonderful set of images showing the location of each mare on the Moon. His website has not been updated since 1999 and the contact email address provided there is no longer valid, and even after a thorough Google search I can find no way to contact him to ask permission to link images here to his site. Even worse, because his hosting site is not secure (http: instead of https:), WordPress does not allow me to link directly to his images so I had to put copies into my media library. Please know that the images shown below are all copyrighted by António Cidadão.

Each image shows north is up and west is to the left. This is direction of increasing longitude and therefore west on the Moon, but in our sky, east is to the left. In other words, these annotated images of the Moon are correctly oriented as they would appear to the unaided eye in the sky in the northern hemisphere. In the rest of this article, we will use the moon-centric east-west convention that Cidadão indicates in his image diagrams.

Let’s take a look at each of the lunar maria from moon-west to moon-east. Their fanciful names were mostly given (and codified in 1651) by the Italian astronomer Giovanni Battista Riccioli (1598-1671). Riccioli chose names related to weather, as it was then believed that the Moon, the closest celestial body to the Earth, exerted an influence on the Earth’s weather. This is perhaps not at all surprising given that the phenomenon of tides had been known since antiquity.

Most of the nearside west portion of the Moon is covered by a mare that is so large that it is given a unique designation: Oceanus for “ocean”.

Oceanus Procellarum, the “Ocean of Storms”

Oceanus Procellarum contains the famously bright crater Aristarchus and the associated Aristarchus Plateau. In the image above you will notice what appears to be a tiny mare close to the limb of the Moon west of the southern part of Oceanus Procellarum. This is the lava-flooded crater Grimaldi.

Mare Orientale, the “Eastern Sea”

South of Grimaldi and straddling the lunar limb is Mare Orientale. It is difficult to see because most of it is on the lunar farside, though libration can sometimes bring its oblique visage into view. The name Orientale, meaning “eastern”, describes its location on the eastward-facing limb of the Moon as seen from Earth, rather than its westward direction as seen from the surface of the Moon.

Mare Humorum, the “Sea of Moisture”

Mare Humorum is located just south of Oceanus Procellarum. It is round and inviting, though no spacecraft has ever landed there.

Mare Nubium, the “Sea of Clouds”

Mare Nubium is east of Mare Humorum. The large crater Bullialdus flanks the western edge of Mare Nubium, and Rupes Recta (the “Straight Wall”) flanks its eastern edge.

Mare Cognitum, the “Sea That Has Become Known”

Mare Cognitum lies between Mare Nubium and Oceanus Procellarum. It was named in 1964 after the Ranger 7 probe took the first U.S. close-up pictures of the Moon’s surface prior to crashing there.

Mare Insularum, the “Sea of Islands”

Mare Insularum is north of Mare Cognitum. Its current name was bestowed upon it in 1976 by lunar geologist Don Wilhelms (1930-). The crater Kepler on its western edge separates Mare Insularum from Oceanus Procellarum. The crater Copernicus is on the northeast side of its western lobe.

Mare Vaporum, the “Sea of Vapors”

Mare Vaporum is the mare closest to the center of the Moon’s nearside. The bright crater Manilius lies towards its northeastern edge and the volcanic crater Hyginus and its associated rille (Rima Hyginus) are immediately to its south.

Mare Imbrium, the “Sea of Rains”

Mare Imbrium was created 3.9 billion years ago when an asteroid some 150 miles across crashed into the Moon. This ancient feature is so large that it forms the right eye of the “Man in the Moon” we see when looking at a full or nearly full moon with our unaided eyes.

Mare Frigoris, the “Sea of Cold”

Mare Frigoris lies north and northeast of Mare Imbrium. The dark crater between them is Plato. It is the mare closest to the north pole of the Moon.

Mare Serenitatis, the “Sea of Serenity”

Now we begin our tour of the eastern hemisphere of the Moon’s nearside. Mare Serenitatis has the distinction of being the landing site of the last human mission to the Moon, Apollo 17, in 1972. It was also the landing site of the Soviet unmanned spacecraft Luna 21 just one month later.

Mare Tranquillitatis, the “Sea of Tranquility”

Mare Tranquillitatis is perhaps the most famous of the lunar maria, as it was there that humans first set foot on the surface of the Moon in 1969. The Apollo 11 landing site is located near its southwest corner.

Mare Nectaris, the “Sea of Nectar”

Mare Nectaris lies south of Mare Tranquillitatis. This small, isolated, and nearly circular mare sports a prominent crater, Theophilus, at its northwest corner.

Mare Fecunditatis, the “Sea of Fertility”

East of Mare Nectaris lies Mare Fecunditatis. Superposed upon Mare Fecunditatis is the striking crater pair Messier and Messier A with two prominent rays evocative of a comet’s tail. Named after the famous French comet hunter Charles Messier (1730-1817), these craters and their associated rays were formed from a grazing impact from the east.

Mare Crisium, the “Sea of Crises”

Mare Crisium is a round and isolated mare that makes it easy to remember why it is called the “Sea of Crises”. The Soviet Luna 24 unmanned sample return mission landed there in 1976. The six ounces of lunar materials it brought back to Earth are the last lunar samples scientists have received.

Mare Anguis, the “Serpent Sea”

Mare Anguis lies just northeast of Mare Crisium and is called the “Serpent Sea” for its serpentine shape rather than the more fanciful name “Sea of Serpents” referred to by some science fiction authors.

Mare Undarum, the “Sea of Waves”

Mare Undarum lies southeast of Mare Crisium. Its uneven texture and lack of uniform smoothness appears to justify its name as “the sea of waves”.

Mare Spumans, the “Foaming Sea”

Mare Spumans lies south of Mare Undarum and east of Mare Fecunditatis. The bright crater Petit on the western side of this tiny mare evinces a bit of foam on “the foaming sea”.

Mare Australe, the “Southern Sea”

Mare Australe hugs the southeastern limb of the lunar nearside. Though obliquely viewed from Earth and wrapping around to the lunar farside, favorable libration makes it visible in its entirety on occasion.

Mare Smythii, “Smyth’s Sea”

Mare Smythii on the eastern limb of the Moon is one of two lunar maria named after people. The lucky honoree is English hydrographer and astronomer William Henry Smyth (1788-1865). The lunar equator passes through Mare Smythii.

Mare Marginis, the “Sea of the Edge”

Mare Marginis lies east of Mare Crisium, right along the lunar limb. The crater Goddard on the northeast side of Mare Marginis exhibits bright deposits on its northeastern side. This crater and its associated deposits can only be seen from Earth during favorable librations.

Mare Humboldtianum, the “Sea of Alexander von Humboldt”

Mare Humboldtianum lies along the northeastern limb of the Moon and is the other lunar mare named after a person. The German astronomer Johann Heinrich von Mädler (1794-1874) named this feature after German geographer and explorer Alexander von Humboldt (1769-1859).

This completes our tour of the 21 maria on the nearside of the Moon.

References

António Cidadão’s Home-Page of Lunar and Planetary Observation and CCD Imaging, Moon-“Light” Atlas.  Retrieved 22 April 2020.
http://www.astrosurf.com/cidadao/moonlight_mare_oceanus.htm

Ewen A. Whitaker, Mapping and Naming the Moon: A History of Lunar Cartography and Nomenclature (Cambridge University Press, 2003).

Shadows Cast by Starlight

Henry Norris Russell (1877-1957) received his Ph.D. at Princeton in 1899 at just 21 years of age. Three years later—in 1902 when he was 24 years old and years before his discovery of the color-luminosity relationship now known as the Hertzsprung-Russell (H-R) diagram—Russell had an interesting article published in the journal Popular Astronomy that shows him already to be a meticulous and perspicacious observational astronomer. This article, completed 118 years ago this day, is reprinted below.


SHADOWS CAST BY STARLIGHT.

HENRY NORRIS RUSSELL.

FOR POPULAR ASTRONOMY.

It has long been known that Venus casts a distinct shadow; and the same thing has sometimes been observed in Jupiter’s case. More recently, it has been stated in the daily press* that shadows cast by Sirius have been seen at the Harvard Observatory in Jamaica, though it was then said that they could probably be seen only where the air is exceptionally clear.

The writer began to investigate this subject, quite independently, last November, and has found that the shadows cast by a number of the brighter fixed stars can be seen without difficulty under ordinary circumstances, provided proper precautions are taken to exclude extraneous light, and to secure the maximum sensitiveness of the observer’s eyes.

* Interview with Professor W.H. Pickering, New York Tribune, Jan. 18, 1902.

The most convenient method of observation is as follows: Choose a window from which the star is visible, while as little light as possible enters from terrestrial sources. Darken the room completely, with the exception of this window. Open the window, and screen down its aperture to an area of a square foot or less. Hold a large piece of white paper in the path of the star’s rays, as far from the opening as possible. The image of the opening will then appear on the paper.

It cannot, however, be well seen until the observer has spent at least ten minutes in the dark, (to rest his eyes from the glare of ordinary lights). The paper should be held within a foot or so of the eyes, as the faint patch of starlight is most easily visible when its apparent area is large. The shadow of any convenient object may now be made to fall on the screen, and may be observed. By holding the object near the window and noticing that its shadow is still sharp, the observer may convince himself that the light which casts the shadow really comes from the star.

By the method above described, the writer has succeeded in distinguishing shadows cast by the following stars, (which are here arranged in order of brightness):

Mag.Mag.
α Canis Majoris (Sirius)– 1.4ζ Orionis1.9
α Bootis (Arcturus)0.0β Tauri1.9
α Aurigae (Capella)0.2γ Geminorum2.0
β Orionis (Rigel)0.3β Canis Majoris2.0
α Canis Minoris (Procyon)0.5α Hydrae2.0
α Orionis* (Betelgeuse)0.8?α Arietis2.0
α Tauri (Aldebaran)1.0κ Orionis2.2
β Geminorum (Pollux)1.1β Leonis2.2
α Virginis (Spica)1.2γ Leonis2.2
α Leonis (Regulus)1.4δ Orionis2.4
ε Canis Majoris1.5η Canis Majoris2.4
α Geminorum (Castor)1.6ζ Argus2.5
ε Orionis1.8α Ceti2.7
δ Canis Majoris1.915 Argus2.9
γ Orionis1.9

* Variable

The groups of stars comprised in the Pleiades and the sword of Orion also cast perceptible shadows. With a wide open window the belt of Orion should be added to this class.

Most of the observations on which this list is based were made at Princeton on February 7th, and 8th, and March 6th, 1902. The first of these nights is recorded as not remarkably clear, the others as very clear. Whenever there was any doubt of the reality of an observed patch of starlight, it was located at least three times, and it was verified each time that the star was really visible from the spot where its light had been located. Many more stars might have been added to the 29 in the foregoing list, had not unfriendly street lamps confined the observations to less than half the sky.

As many of the stars observed were at a low altitude, it may be concluded that a star of the 3rd magnitude, if near the zenith, would cast a perceptible shadow.

In attempting to get a shadow from these faint stars, the opening of the window should be narrowed to a width of a few inches, so as to cut off as much as possible of the diffused light of the sky. Care should be taken not to look at the sky while observing, as it is bright enough to dazzle the eyes for some little time.

By observing these precautions, the writer has been able to detect shadows cast by Sirius, Arcturus and Capella on moonlight nights,—in the case of Sirius, even when the Moon shone into the room.

The actual brightness of the screen, even when illuminated by Sirius, is very small in comparison with that of the “dark” background of the sky, as seen by the naked eye. White paper reflects about 80 per cent of the incident light. From photometric considerations, a disk of this material 1° in apparent diameter, illuminated perpendicularly by Sirius, should send us about 1/16,000 as much light as the star.

But, according to Professor Newcomb’s determination*, an area of sky 1° in diameter, remote from the Milky Way, sends us 9/10 as much light as a 5th magnitude star, or about 1/400 of the light of Sirius. Hence the sky is about 40 times as bright, area for area, as the paper illuminated by Sirius. The illumination of the paper by a 1st magnitude star is about 1/400 as bright, and by a 3d magnitude star less than 1/2000 as bright, area for area, as the “dark” background of the sky.

* Astrophysical Journal, December 1901.

This faint light, as might be anticipated, shows no perceptible color. The light of the white stars β and γ Orionis and the red star α Orionis does not differ sensibly in quality; but the light of the red star appears much fainter than the star’s brightness, as directly seen, would lead one to anticipate. On the screen, the light of α Orionis is much fainter than that of β, and only a little brighter than that of γ, while by direct vision α is much nearer to β than to γ in brightness. As β is 1 ½ magnitudes brighter than γ, it appears that, as measured by the intensity of its light on a screen, α Orionis is at least half a magnitude, perhaps a whole magnitude, fainter than when compared with the neighboring white stars by direct vision.

Such a result might have been anticipated à priori, since, in the ease of such faint lights as are here dealt with, the eye is sensitive to the green part of the spectrum alone, and this is relatively brighter in the spectrum of a white star than of a red one.

A much more interesting example of the accordance of theoretical prediction with observation is afforded by another phenomenon discovered by the writer, which is not hard to observe.

A surface illuminated by a planet—Venus for example—appears uniformly and evenly bright, but in the case of a fixed star, there are marked variations in brightness, so that the screen appears covered with moving dark markings.

This was predicted many years ago by Professor Young, in discussing the twinkling of the stars. He says*: “If the light of a star were strong enough, a white surface illuminated by it would look like the sandy bottom of a shallow, rippling pool of water illuminated by sunlight, with light and dark mottlings which move with the ripples on the surface. So, as we look toward the star, and the mottlings due to the irregularities of the air move by us, we see the star alternately bright and faint; in other words, it twinkles.”

General Astronomy, page 538 (edition of 1898).

It would be difficult to give a better description of the observed phenomenon than the one contained in the first part of the above quotation. It need only be added that the dark markings are much more conspicuous than the bright ones. This agrees with the fact that a star more frequently seems to lose light while twinkling than to gain it.

Sirius is the only star whose light is bright enough to make these light and dark mottlings visible without great difficulty, though the writer has seen them in the light of Rigel and Procyon. With Sirius they have been seen every time the star’s light has been observed on a moonless night. They are much more conspicuous when the star is twinkling violently than on nights when the air is steady. In the latter case there are only faint irregular mottlings, whose motion produces a flickering effect. More usually there appear also ill-defined dark bands, two or three inches wide. These are never quite straight nor parallel but usually show a preference for one or two directions, sometimes dividing the screen into irregular polygons. On some nights they merely seem to oscillate, but on others they have a progressive motion, which may be at any angle with their own direction. The rate of motion is very variable, but is greatest on windy nights,—another evidence of the atmospheric origin of the bands.

The best nights for observing these bands occur when the stars are twinkling strongly, and there is not much wind. The directions given above for observing shadows should be somewhat modified in this case.

If the room is not at the same temperature as the outer air, the window should be kept closed, as otherwise most of what is seen will be due to the air-currents near it. It is also desirable to have an area of star-light at least a foot square to see the bands in, so that a good sized part of the window should be left clear.

If Sirius is unavailable, Arcturus and Vega are probably the best stars in whose light to attempt to see the bands.

PRINCETON, N. J., March 24, 1902.

Happy Birthday, AAAA!

The first meeting of the Ames Area Amateur Astronomers (AAAA) took place 40 years ago today: Saturday, June 2, 1979. Central Junior High Earth Science teacher Jack Troeger and Welch Junior High Earth Science Teacher Ron Bredeson held the first meeting in Jack’s classroom in the building that is now the Ames City Hall. This was a great start to a great astronomy club. Here’s to the next 40 years!

And, we just passed another important milestone in AAAA history. The grand opening of the original McFarland Park Observatory took place 35 years ago on Memorial Day, Monday, May 28, 1984. Back then, the pavement ended at the intersection of Dayton Rd. & County Road E-29, northeast of Ames, Iowa, and it was gravel the rest of the way.

The first McFarland Park Observatory with its second telescope, a 12.5-inch Newtonian & Cassegrain telescope. The first telescope was a 13.1-inch Coulter Odyssey Dobsonian.
Observatory manager Jim Doggett and AAAA president David Oesper inside the original McFarland Park Observatory. Lower right photo is Julie Oesper and Katie Dilks watching the spectacular aurora borealis display the evening of November 8, 1991.

The AAAA purchased a backyard-observatory silo-top dome from Glen Hankins in Nevada on Saturday, September 27, 1980, and then-Ranger (and later Story County Conservation Director) Steve Lekwa of McFarland Park was instrumental in allowing the AAAA to build its observatory at its present site at McFarland Park. The much-improved replacement roll-off-roof observatory, named after club members and benefactors Bertrand & Mary Adams, was completed in 2000. The only part of the original observatory structure that remains is the telescope pier!

Scintillating Stars But Not Planets

Aristotle (384 BC – 322 BC) may have been the first person to write that stars twinkle but planets don’t, though our understanding of twinkling has evolved since he explained that “The planets are near, so that the visual ray reaches them in its full vigour, but when it comes to the fixed stars it is quivering because of the distance and its excessive extension.”

John Stedman (1744-1797), a controversial and complicated figure to be sure, writes the following dialog between teacher and student in The Study of Astronomy, Adapted to the capacities of youth (1796):

PUPIL.  How is the twinkling of the stars in a clear night accounted for?

TUTOR.   It arises from the continual agitation of the air or atmosphere through which we view them; the particles of air being always in motion, will cause a twinkling in any distant luminous body, which shines with a strong light.

PUPIL.  Then, I suppose, the planets not being luminous, is the reason why they do not twinkle.

TUTOR.   Most certainly.  The feeble light with which they shine is not sufficient to cause such an appearance.

Still not quite right, but closer to our current understanding. Our modern term for “twinkling” is atmospheric scintillation, which is changes in a star’s brightness caused by curved wavefronts focusing or defocusing starlight.

Scintillation is caused by refractive index variations (due to differences in pressure, temperature, and humidity) of “pockets” of air passing in front of the light path between star and observer at a typical height of about 5 miles. These pockets are typically about 3 inches across, so from the naked eye observer’s standpoint, they subtend an angle of about 2 arcseconds.

The largest angular diameters of stars are on the order of 50 milliarcseconds1 (R Doradus, Betelgeuse, and Mira), and only seventeen stars have an an angular diameter larger than 1 milliarcsecond. So, it is easy to see how cells of air on the order of 2 arcseconds across moving across the light path could cause the stars to flicker and flash as seen with the unaided eye.

The five planets that are easily visible to the unaided eye (Mercury, Venus, Mars, Jupiter, and Saturn) have angular diameters that range from 3.5 arcseconds (Mars, at its most distant) up to 66 arcseconds (Venus, at its closest). Since the disk of a planet subtends multiple air cells, the different refractive indexes tend to cancel each other out, and the planet shines with a steady light.

From my own experience watching meteors many nights with my friend Paul Martsching, our reclining lawn chairs just a few feet apart, I have sometimes seen a principal star briefly brighten by two magnitudes or more, with Paul seeing no change in the star’s brightness, and vice versa.


Stedman’s dialogue next turns to the distances to the nearest stars.

PUPIL.  Have the stars then light in themselves?

TUTOR.   They undoubtedly shine with their own native light, or we should not see even the nearest of them: the distance being so immensely great, that if a cannon-ball were to travel from it to the sun, with the same velocity with which it left the cannon, it would be more than 1 million, 868 thousand years, before it reached it.

He adds a footnote:

The distance of Syrius is 18,717,442,690,526 miles.  A cannon-ball going at the rate of 1143 miles an hour, would only reach the sun in about 1,868,307 years, 88 days.

Where Stedman comes up with the velocity of a cannon-ball is unclear, but the Earth’s rotational speed at the equator is 1,040 mph, close to Stedman’s cannon-ball velocity of 1,143 mph. He states the distance to the brightest star Sirius—probably then thought to be the nearest star—is 18,717,442,690,526 miles or 3.18 light years, a bit short of the actual value of 8.60 light years. The first measurements of stellar parallax lie 42 years in the future when Stedman’s book was published.

1 1 milliarcsecond (1 mas) = 0.001 arcsecond

References
Aristotle, De Caelo, Book 2, chap.8, par. 290a, 18
Crumey, A., 2014, MNRAS, 442, 2600
Dravins, D., Lindegren, L., Mezey, E., Young, A. T., 1997a, PASP, 109, 173
Ellison, M. A., & Seddon, H., 1952, MNRAS, 112, 73
Stedman, J., 1796, The Study of Astronomy, Adapted to the capacities of youth

Rhapsody in Blue

American composer George Gershwin left us much too soon at the young age of 38. He died of a brain tumor in 1937, and eight years after his death a somewhat fictionalized movie about his life was released in 1945, Rhapsody in Blue.

One remarkable aspect of this movie is a number of people who knew Gershwin were in the movie as themselves: Oscar Levant, Paul Whiteman (who premiered Rhapsody in Blue), Hazel Scott, Anne Brown, Al Jolson, George White, and Elsa Maxwell. It is a love letter to this remarkable composer and musician.

Robert Alda (father of Alan Alda) turns in a great performance as George Gershwin, as does Joan Leslie as his fictionalized love interest Julie Adams.

Robert Alda as George Gershwin and Joan Leslie as Julie Adams in Rhapsody in Blue (1945)

Strong performances were also turned in by Morris Carnovsky as George Gershwin’s father, Albert Bassermann as his fictionalized teacher Professor Franck (perhaps patterned in part after both Charles Hambitzer and Rubin Goldmark), and Herbert Rudley as Ira Gershwin.

And then there’s the wonderful music of George Gershwin throughout the film, including much of An American in Paris, a personal favorite of mine. I’ll bet you’ll hear familiar songs that you didn’t even know were written by Gershwin!

I loved this movie. Unfortunately, it is not available through either Netflix or Amazon streaming, but you can purchase a high-quality DVD for $12.99 from Warner Brothers.

https://www.wbshop.com/products/rhapsody-in-blue

If you don’t know much about George Gershwin, this movie is a good starting point. After you watch it, I guarantee you’ll want to learn more about the real George Gershwin and his music. Enjoy!

Les Misérables

There have been many film adaptations of Victor Hugo’s timeless novel, Les Misérables, but after watching the 1935 film starring Fredric March and Charles Laughton last night, I am in no rush to see any of the others. It is, quite simply, perfect.

This movie says more in one hour and forty-eight minutes than most other movies (especially more recent ones) say in two or three hours. A riveting tale of unjust laws, poverty, inhumanity, cruelty, compassion, love, mercy, doubt, and morality, this is one of the most moving and inspiring movies I have ever seen. And just as relevant for us to today as it was in 1935 and when Victor Hugo wrote the book, first published in 1862.

We need movies like this to remind us (and in such complex and jaded times as these we do need constant reminding) that idealism can help each of us navigate through life, and—no matter what burdens we bear—to make the world a better place. Not a single minute in this movie is wasted, so artfully is each and every scene of the movie constructed. If you tire of (and are horrified by) the seemingly endless stream of dystopian prognostications in recent years, this movie is the perfect antidote. There is an alternative to a ruined world, and that change begins with you and me right now.

https://dvd.netflix.com/Movie/Les-Miserables/70073445

https://www.amazon.com/Miserables-Richard-Boleslawski/dp/B076LJ6Y7V/

All of the film adaptations of Les Misérables, including this one, have a number of departures from the original novel by Victor Hugo. Behind every great movie there is usually an even greater book, and I have been remiss in never having read Hugo’s classic. That deficiency will be rectified soon.

Desiderata

The word desideratum has been a part of the English language since at least 1651, according to the Oxford English Dictionary, which provides this definition:

Something for which a desire or longing is felt; something wanting and required or desired.

This word comes from the Latin dēsīderātum “thing desired”, and its plural is desiderata.

The French astronomer Auguste Charlois (1864-1910) discovered the asteroid 344 Desiderata on 15 Nov 1892 at the Nice Observatory, in southeastern France near the border with Italy. Like most of his 99 asteroid discoveries between 1887 and 1904, it is named to honor a woman. In this case, that would be Désirée Clary (1777-1860), French woman who became Queen Desideria of Sweden.

On 25 Feb 2019, I recorded 14.1-magnitude 344 Desiderata passing in front of the 14.6-magnitude star UCAC4 639-020401 in the constellation Auriga. Right before the event, star and asteroid formed a 13.6-magnitude blended image, and when the asteroid covered up the star, the brightness dipped 0.5 magnitude to the brightness of the asteroid alone. This great cover-up event lasted 16.8 seconds. Here’s a light curve of the event as a function of time.

Light curve of asteroid 344 Desiderata passing in front of UCAC4 639-020401 in Auriga

That dip to the right (after) the asteroid covered up the star suggests that a smaller satellite of the asteroid might have also passed in front of the star. Alas, it is only noise. We can tell this by looking at the light curve of a nearby comparison star at the same time.

Wind gust caused a dip in brightness of both stars at the same time after the main occultation event
A view of just the comparison star clearly showing the dip in brightness from a wind gust

Here is the smoothed and fitted light curve of the asteroid occultation event.

Asteroid occultation of the star UCAC4 639-020401 by the asteroid 344 Desiderata on 25 Feb 2019


Max Ehrmann (1872-1945) wrote a prose poem Desiderata (Latin: “things desired”) in 1927 that has since become well known, and for good reason.

Desiderata

Go placidly amid the noise and the haste, and remember what peace there may be in silence.  As far as possible, without surrender, be on good terms with all persons.

Speak your truth quietly and clearly; and listen to others, even to the dull and the ignorant; they too have their story.

Avoid loud and aggressive persons; they are vexatious to the spirit. If you compare yourself with others, you may become vain or bitter, for always there will be greater and lesser persons than yourself.

Enjoy your achievements as well as your plans. Keep interested in your own career, however humble; it is a real possession in the changing fortunes of time.

Exercise caution in your business affairs, for the world is full of trickery. But let this not blind you to what virtue there is; many persons strive for high ideals, and everywhere life is full of heroism.

Be yourself. Especially do not feign affection. Neither be cynical about love; for in the face of all aridity and disenchantment, it is as perennial as the grass.

Take kindly the counsel of the years, gracefully surrendering the things of youth.

Nurture strength of spirit to shield you in sudden misfortune. But do not distress yourself with dark imaginings. Many fears are born of fatigue and loneliness.

Beyond a wholesome discipline, be gentle with yourself. You are a child of the universe no less than the trees and the stars; you have a right to be here.

And whether or not it is clear to you, no doubt the universe is unfolding as it should. Therefore be at peace with God, whatever you conceive Him to be. And whatever your labors and aspirations, in the noisy confusion of life, keep peace in your soul. With all its sham, drudgery and broken dreams, it is still a beautiful world. Be cheerful. Strive to be happy.

Thank the Sumerians

Over five thousand years ago, the Sumerians in the area now known as southern Iraq appear to have been the first to develop a penchant for the numbers 12, 24, 60 and 360.

It is easy to see why. 12 is the first number that is evenly divisible by six smaller numbers:

12 = 1×12, 2×6, 3×4 .

24 is the first number that is evenly divisible by eight smaller numbers:

24 = 1×24, 2×12, 3×8, 4×6 .

60 is the first number than is evenly divisible by twelve smaller numbers:

60 = 1×60, 2×30, 3×20, 4×15, 5×12, 6×10 .

And 360 is the first number that is evenly divisible by twenty-four smaller numbers:

360 = 1×360, 2×180, 3×120, 4×90, 5×72, 6×60, 8×45, 9×40, 10×36, 12×30, 15×24, 18×20 .

And 360 in a happy coincidence is just 1.4% short of the number of days in a year.

We have 12 hours in the morning, 12 hours in the evening.

We have 24 hours in a day.

We have 60 seconds in a minute, and 60 minutes in an hour.

We have 60 arcseconds in an arcminute, 60 arcminutes in a degree, and 360 degrees in a circle.


The current equatorial coordinates for the star Vega are

α2019.1 = 18h 37m 33s
δ2019.1 = +38° 47′ 58″

Due to precession, the right ascension (α) of Vega is currently increasing by 1s (one second of time) every 37 days, and its declination (δ) is currently decreasing by 1″ (one arcsecond) every 5 days.

With right ascension, the 360° in a circle is divided into 24 hours, therefore 1h is equal to (360°/24h) = 15°. Since there are 60 minutes in an hour and 60 seconds in a minute, and 60 arcminutes in a degree and 60 arcseconds in an arcminute, it follows that 1m = 15′ and 1s = 15″.

Increasingly, you will see right ascension and declination given in decimal, rather than sexagesimal, units. For Vega, currently, this would be

α2019.1 = 18.62583h
δ2019.1 = +38.7994°

Or, both in degrees

α2019.1 = 279.3875°
δ2019.1 = +38.7994°

Or even radians

α2019.1 = 4.876232 rad
δ2019.1 = 0.677178 rad

Even though the latter three forms lend themselves well to computation, I still prefer the old sexagesimal form for “display” purposes, and when entering coordinates for “go to” at the telescope.

There is something aesthetically appealing about three sets of two-digit numbers, and, I think, this form is more easily remembered from one moment to the next.

For the same reason, we still use the sexagesimal form for timekeeping. For example, as I write this the current time is 12:25:14 a.m. which is a more attractive (and memorable) way to write the time than saying it is 12.4206 a.m. (unless you are doing computations).

That’s quite an achievement, developing something that is still in common use 5,000 years later.

Thank the Sumerians!

Historical Astronomy Magazines Online and DVD

Excellent astronomy magazines have come and gone throughout the past several hundred years, and the time has come to start digitizing microfilm, microfiche, or printed copies of all these magazines and journals, and make them available at an affordable price to individuals and institutions on DVD and via the Internet.  First on my list? Popular Astronomy, which was published from 1893 until 1951 at Carleton College in Northfield, Minnesota, a worthy predecessor to Sky & Telescope.

Some of the volumes of Popular Astronomy are available online, thanks to the HathiTrust Digital Library:

Volume 1, 1893
Volume 2, 1894
Volume 3, 1895
Volume 4, 1896
Volume 5, 1897
Volume 6, 1898
Volume 7, 1899
Volume 8, 1900
Volume 9, 1901
Volume 10, 1902
Volume 11, 1903
Volume 12, 1904
Volume 13, 1905
Volume 14, 1906
Volume 15, 1907
Volume 16, 1908
Volume 17, 1909
Volume 18, 1910
Volume 19, 1911
Volume 20, 1912
Volume 21, 1913
Volume 22, 1914
Volume 23, 1915
Volume 24, 1916
Volume 25, 1917
Volume 26, 1918
Volume 27, 1919
Volume 28, 1920
Volume 29, 1921
Volume 30, 1922
Volume 31, 1923
Volume 32, 1924
Volume 33, 1925
Volume 34, 1926
Volume 35, 1927
Volume 36, 1928
Volume 37, 1929
Volume 38, 1930
Volume 39, 1931
Volume 40, 1932
Volume 41, 1933
Volume 42, 1934
Volume 43, 1935
Volume 44, 1936
Volume 45, 1937
Volume 46, 1938
Volume 47, 1939
Volume 48, 1940
Volume 49, 1941
Volume 50, 1942
Volume 51, 1943
Volume 52, 1944
Volume 53, 1945
Volume 54, 1946
Volume 55, 1947
Volume 56, 1948
Volume 57, 1949
Volume 58, 1950
Volume 59, 1951

Project Gutenberg

Over 56,000 historical books and other documents, most published prior to 1923, are available online for downloading or browsing at Project Gutenberg (http://www.gutenberg.org), with more being added all the time. A quick search of the term “astronomy” yields the following:

The Discovery of a World in the Moone: Or, A Discovrse Tending To Prove That ‘Tis Probable There May Be Another Habitable World In That Planet (1638)
John Wilkins (1614-1672)

The Study of Astronomy, Adapted to the capacities of youth (1796)
John Gabriel Stedman (1744-1797)

The Martyrs of Science, or, The lives of Galileo, Tycho Brahe, and Kepler (1841)
David Brewster (1781-1868)

Lectures on Astronomy (1854)
The Wit and Humor of America, Volume V. (1911)
George Horatio Derby (1823-1861), writing under the name of John Phoenix
Marshall Pinckney Wilder (1859-1915), editor

Letters on Astronomy: In which the Elements of the Science are Familiarly Explained in Connection with Biographical Sketches of the Most Eminent Astronomers (1855)
Denison Olmsted (1791-1859)

The Uses of Astronomy: An Oration Delivered at Albany on the 28th of July, 1856 (1856)
Edward Everett (1794-1865)

Cosmos: A Sketch of the Physical Description of the Universe, Vol. 1 (1858)
Alexander von Humboldt (1769-1859)

Curiosities of Science, Past and Present: A Book for Old and Young (1858)
John Timbs (1801-1875)

Astronomy for Young Australians (1866)
James Bonwick (1817-1906)

Meteoric astronomy: A treatise on shooting-stars, fire-balls, and aerolites (1867)
Daniel Kirkwood (1814-1895)

Popular Books on Natural Science: For Practical Use in Every Household, for Readers of All Classes (1869)
Aaron David Bernstein (1812-1884)

Half-hours with the Telescope: Being a Popular Guide to the Use of the Telescope as a Means of Amusement and Instruction (1873)
Richard Anthony Proctor (1837-1888)

Astronomical Myths: Based on Flammarions’s “History of the Heavens” (1877)
John Frederick Blake (1839-1906)
Camille Flammarion (1842-1925)

New and Original Theories of the Great Physical Forces (1878)
Henry Raymond Rogers (1822-1901)

Recreations in Astronomy: With Directions for Practical Experiments and Telescopic Work (1879)
Henry White Warren (1831-1912)

The Sidereal Messenger of Galileo Galilei and a Part of the Preface to Kepler’s Dioptrics Containing the Original Account of Galileo’s Astronomical Discoveries (1880)
Galileo Galilei (1564-1642)
Johannes Kepler (1571-1630)
Edward Stafford Carlos ((1842–1927), translator

Sir William Herschel: His Life and Works (1880)
Edward Singleton Holden (1846-1914)

Popular Scientific Recreations in Natural Philosophy, Astronomy, Geology, Chemistry, etc., etc., etc. (1881)
Gaston Tissandier (1843-1899)

Publications of the Astronomical Society of the Pacific, Volume 1 (1889)
Astronomical Society of the Pacific (1889-)

A Textbook of General Astronomy for Colleges and Scientific Schools (1889)
Charles Augustus Young (1834-1908)

Time and Tide: A Romance of the Moon (1889)
Robert Stawell Ball (1840-1913)

Astronomy with an Opera-glass: A Popular Introduction to the Study of the Starry Heavens with the Simplest of Optical Instruments (1890)
Garrett Putman Serviss (1851-1929)

Pioneers of Science (1893)
Sir Oliver Joseph Lodge (1851-1940)

Great Astronomers (1895)
Robert Stawell Ball (1840-1913)

The Astronomy of Milton’s ‘Paradise Lost’ (1896)
Thomas Nathaniel Orchard, M.D.

Myths and Marvels of Astronomy (1896)
Richard Anthony Proctor (1837-1888)

The Story of Eclipses (1899)
George Frederick Chambers (1841-1915)

The Tides and Kindred Phenomena in the Solar System: The Substance of Lectures Delivered in 1897 at the Lowell Institute, Boston, Massachusetts (1899)
Sir George Howard Darwin (1845-1912)

The Royal Observatory, Greenwich: A Glance at Its History and Work (1900)
Edward Walter Maunder (1851-1928)

The Story of the Heavens (1900)
Robert Stawell Ball (1840-1913)

Other Worlds: Their Nature, Possibilities and Habitability in the Light of the Latest Discoveries (1901)
Garrett Putman Serviss (1851-1929)

Pleasures of the telescope: An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers (1901)
Garrett Putman Serviss (1851-1929)

A Text-Book of Astronomy (1903)
George Cary Comstock (1855-1934)

Astronomical Discovery (1904)
Herbert Hall Turner (1861-1930)

A New Astronomy (1906)
David Peck Todd (1855-1939)

New Theories in Astronomy (1906)
William Stirling (1822-1900)

Side-Lights on Astronomy and Kindred Fields of Popular Science (1906)
Simon Newcomb (1835-1909)

The Children’s Book of Stars (1907)
Geraldine Edith Mitton (1868-1955)

Mathematical Geography (1907)
Willis Ernest Johnson (1869-1951)

Astronomical Instruments and Accessories (1908)
William Gaertner and Company (1896-)
now Gaertner Scientific Corporation

The Astronomy of the Bible: An Elementary Commentary on the Astronomical References of Holy Scripture (1908)
Edward Walter Maunder (1851-1928)

A Popular History of Astronomy During the Nineteenth Century, Fourth Edition (1908)
Agnes Mary Clerke (1842-1907)

Astronomical Curiosities: Facts and Fallacies (1909)
John Ellard Gore (1845-1910)

The Future of Astronomy (1909)
Edward Charles Pickering (1846-1919)

History of Astronomy (1909)
George Forbes (1849-1936)

Astronomy for Amateurs (1910)
Camille Flammarion (1842-1925)

Astronomy of To-day: A Popular Introduction in Non-Technical Language (1910)
Cecil Goodrich Julius Dolmage (1870-1908)

The World’s Greatest Books — Volume 15 — Science (1910)
Arthur Mee (1875-1943), editor
Sir John Alexander Hammerton (1871-1949), editor

The Science of the Stars (1912)
Edward Walter Maunder (1851-1928)

Are the Planets Inhabited? (1913)
Edward Walter Maunder (1851-1928)

Woman in Science: With an Introductory Chapter on Woman’s Long Struggle for Things of the Mind (1913)
John Augustine Zahm (1851-1921), writing under the name H. J. Mozans

A Field Book of the Stars (1914)
William Tyler Olcott (1873-1936)

An Introduction to Astronomy (1916)
Forest Ray Moulton (1872-1952)

Scientific Papers by Sir George Howard Darwin. Volume V. Supplementary Volume (1916)
Sir George Howard Darwin (1845-1912)
Ernest William Brown (1866-1938), contributor
Sir Francis Darwin (1848-1925), contributor

The gradual acceptance of the Copernican theory of the universe (1917)
Dorothy Stimson (1890-1988)

Astronomical Lore in Chaucer (1919)
Florence Marie Grimm

Lectures on Stellar Statistics (1921)
Carl Vilhelm Ludwig Charlier (1862-1934)

The Star People (1921)
Gaylord Johnson

Terrestrial and Celestial Globes Volume 1: Their History and Construction Including a Consideration of their Value as Aids in the Study of Geography and Astronomy (1921)
Edward Luther Stevenson (1858-1944)

Terrestrial and Celestial Globes Volume 2: Their History and Construction Including a Consideration of their Value as Aids in the Study of Geography and Astronomy (1921)
Edward Luther Stevenson (1858-1944)

Astronomy for Young Folks (1922)
Isabel Martin Lewis (1881-1966)

Astronomy: The Science of the Heavenly Bodies (1922)
David Peck Todd (1855-1939)

The New Heavens (1922)
George Ellery Hale (1868-1938)

Watchers of the Sky (1922)
Alfred Noyes (1880-1958)

Biography of Percival Lowell (1935)
Abbott Lawrence Lowell (1856-1943)