Cumberland Times-News

Bob Doyle - Astronomy

February 16, 2013

Almanacs are useful, especially Banneker’s

If one could time travel back two centuries, you would be sure to find two books in most rural households — the Bible and an Almanac. Back then farmers used an almanac to tell them the moon’s phases (lighted shapes).

It is was widely thought that one should plant crops that appear above the ground (corn, wheat, tomatoes) during the growing or waxing phases of the moon. The moon seems to grow in lighted width for about two week (from new moon to full moon) in the evening sky.

Conversely, those plants that grow under the soil (potatoes, turnips and carrots) would thrive if they were planted during the shrinking or waning phases of the moon.

The moon seems to shrink for about two weeks (full moon to new moon), where it is best seen in the sky after midnight. While scientific research has failed to back up these practices, these ideas caused farmers to spread out their planting over a month.

With this being Black History Month, the almanacs by Benjamin Banneker make for a wonderful story.

Benjamin was the son of Molly Welsh and an African man named Banakaa. Molly was an English indentured servant who came to America to serve out her seven years of labor.

She then became a free person and bought a farm of her own. She also bought an African slave named Banakaa to help her with the farm. Molly and her worker fell in love and Benjamin was born several decades before the American Revolution.

Molly taught Benjamin to read the Bible. Benjamin was an eager learner and he borrowed math books from nearby farm families. Benjamin continued to work the farm for decades as well as learning astronomical mathematics.

Benjamin produced an almanac for several years in the 1790s that was recognized by noted Americans.

As for current almanacs, there are a number of small almanacs that cost from $5 to $7. They are known for their weather predictions on a day by day issue.

But the best part of these small almanacs are their tables of sunrise, sunset, moon rise or set (usually one during a given night). The almanac I bought for $5 gives sunrise, sunset and the night moon event for latitude 40 degrees North and longitude 75 degrees West.

To convert these times for Cumberland, you just add 15 minutes. Then the almanac times are within a minute or two of what is printed in the AccuWeather forecast each day in the Cumberland Times-News.

Of the larger and more expensive almanacs, my favorite is The World Almanac (about $13). You will not find times of sunrise, sunset, moon rise/set (during the night) there.

But there is a lengthy list of celestial events for 2013, which includes the moon-planet encounters. There are also tables of the rising times and setting times of the bright planets for every 10 days.

Another excellent section are up to date summaries of all the planets (both the eight regular planets and the five dwarf planets). This section won’t quickly go out of date as celestial events, planet rising/setting times which change from year to year.

The treatment of major space exploration focuses on the names of the missions and their findings is very useful.

The Time Almanac, done in association with Encyclopedia Britannica costs $1 more than the World Almanac. In its Nature, Science, Medicine and Technology portion, there is a very nice treatment of Calendars, including the Jewish and Chinese calendars (both tied to the lunar cycle).

The list of Astronomical Phenomena for 2013 lists not only the date but the hour (in English time, five hours ahead of our standard time).

The sections on the planets is also fine, but doesn’t include the dwarf planets like Pluto. There is a very nice treatment of the history of manned spaceflight in the Time Almanac.

One of the best things about the two large almanacs above is that one of them is likely in the reference section of a public library.

SKY SIGHTS AHEAD: Tomorrow night the half full evening moon will appear below the bright planet Jupiter. If you have binoculars and lie on a tarp, you can comfortably see the larger lunar craters and spot one or two of the big moons of Jupiter.

The moon and Jupiter will also be in the same part of the sky tonight and Tuesday night.

The planet Saturn is rising in the East just before midnight. The best time to see Saturn’s rings with a telescope will be in the southern dawn sky when Saturn will be about half way up in the sky.

To the right of Saturn is the bright, twinkling star Spica (of Virgo). Saturn, comparable in brightness to Spica will shine steadily.

Bob Doyle invites any readers comments and questions. E-mail him at rdoyle@frostburg.edu . He is available as a speaker on his column topics.

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