Berthoud Weekly Surveyor | Covering all the angles in the Garden Spot

Community’s eclipse party tradition continued at Pioneer Museum

August 24, 2017 | Local News

By Mark French

The Surveyor

Berthoud’s first “eclipse party” took place at banker John Bunyan’s backyard observatory in July 1915. On August 21 the Berthoud Historical Society continued that tradition with a three-hour eclipse viewing party at the Little Thompson Valley Pioneer Museum.

The solar eclipse viewing event the Berthoud Historical Society held at the Little Thompson Valley Pioneer Museum on Aug. 21, 2017, was not the first such event to be held in Berthoud. The first “eclipse party” took place at John Bunyan’s backyard observatory at 601 Eighth St. on the evening of July 15, 1935. Following the celestial celebration the Berthoud Bulletin reported, “John Bunyan had a number of guests at his observatory for several phases of eclipse. The night was ideal for observation.”

Mention of Bunyan’s astronomical observations was made in the local newspaper with great frequency in the 1930s and 1940s. The Denver Post also got into the act in May 1935 when it featured photographs of Bunyan’s observatory and the astronomer with one of his telescopes. The photographs’ caption read: “Money isn’t everything to John Bunyan of Berthoud, Colorado, even though he is a banker. He’s a banker by day, an astronomer by night. Study of the heavenly bodies held such a fascination for Bunyan that he built at the rear of his home an astronomical observatory which is probably the most completely equipped of its size in the United States. When he wishes to make observations, sections of the roof over the main room is rolled to one side on a track, as shown here, and the telescope is raised. Below Bunyan is showed at his 10-inch Cassegrainian telescope.”

In July 1935 Bunyan wrote an article for the Berthoud Bulletin that provided readers of the newspaper with details about an upcoming lunar eclipse. Bunyan wrote, “There will be a total eclipse of the moon the evening of July 15, which will almost be central and the period of totality will be an hour and forty minutes.

“Following are the times of the several phases of the eclipse, Mountain Standard Time: Moon enters penumbra July 15 at 7:15 p.m.; Moon enters umbra 8:12; Total eclipse begins at 9:09; Middle of eclipse 9:59; Total eclipse ends 10:50; Moon leaves umbra 11:47; Moon leaves penumbra July 18, 12:43 a.m.

“Because the diameter of the sun is much larger than the diameter of the earth, the earth casts a conical shadow into space that is always opposite the sun. At the distance of the moon from earth the diameter of this shadow is about 5,700 miles. If the plane of the moon’s orbit around the earth were coincident with the plane of the earth’s orbit around the sun there would be an eclipse of the moon at every full moon. However, the plane of the moon’s orbit is inclined a little over 5 degrees to the plane of the earth’s orbit so that usually the earth’s shadow passes either above or below the moon, so that the moon is not ordinarily eclipsed.

“The points where the earth’s orbit and the moon’s orbit intersect are called the moon’s nodes and this time the moon is very close to one of its nodes when it is full. As a result the moon will pass very nearly through the center of the earth’s shadow and inasmuch as the moon moves in its orbit about one moon breadth per hour it will be wholly in the shadow for about an hour and forty minutes. Even when totally eclipsed, the moon can be seen as a dull copper colored object due to the sun’s rays being bent or refracted by passing through the earth’s atmosphere.  JOHN BUNYAN.”

Even though Monday’s celestial event was a solar rather than lunar eclipse, the Berthoud Historical Society continued the community’s decades-old “eclipse party” tradition with a three-hour viewing at the Little Thompson Valley Pioneer Museum. BHS Museum director, Karen Lloyd D’Onofrio, estimated 50 people of all ages participated in the event that included the construction of pin-holes cameras (child’s craft activity), eclipse viewing through safety glasses, and opportunities to examine Bunyan’s original Brashear telescope in a replicate of his observatory.


For more information on free stargazing nights at the Bunyan Observatory, call the Little Thompson Valley Pioneer Museum at 970-532-2147.


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