Tag: NASA

Posted in From The Editor's Desk, Science

Bonus: “Maunder Minimum”, Cartography, and Hevelius

Posted on by Book Doctor Dara

Earlier this evening, I blogged about Cartography and the Moon, 1647 and Johannes Hevelius (1611-1687). While doing the research, I came across this image of Hevelius’ earliest drawing of sunspots. Since it wasn’t “Moon” related, my son, Jason ( check out his blog, “Jason’s Blog- Work in Progress”), said I should post it as a bonus feature. So, here it is!

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AN EARLY DRAWING of the Sun and sunspots by Johannes Hevelius. Here Hevelius shows the path and changes in sunspots that crossed the disk of the Sun between May 22 and May 31 in 1643 as they were seen in Danzig. – NASA

So, what is the “Maunder Minimum“? ” The number of sunspots observed on the solar surface varies fairly regularly, with an average period of 11-years. However, if we look at the variation of the sunspot number with time, we find that for a period of about 70 years, from A.D. 1645 to 1715, practically no sunspots have been observed. In other words, during this time the solar cycle has been interrupted. This period of time is called the Maunder Minimum.“[1]

Did You Know?

In 1679 the English astronomer Edmond Halley visited Hevelius and compared the use of a sextant having telescopic sights with Hevelius’ sextant with open sights. Hevelius showed that he could determine stellar positions about as accurately without a telescope as Halley could with one.

[1] https://www.cora.nwra.com/~werne/eos/text/maunder.html

 

Editor’s Note: Featured image The Photosphere and Sun-spots is by S.P. Lngley | The Photosphere and Sun-spots | Popular Science Monthly, vol. 5 (September 1874)

Posted in From The Editor's Desk, Science

Cartography and the Moon, 1647

Posted on by Book Doctor Dara

This Old Map…

In 1647, Polish astronomer Johannes Hevelius published the Selenographia sive Lunae Descriptio (Selenography or the description of the moon). [Ed Note: Selenography is named after the Greek moon goddess Selene[1].]

Hevelius
Johannes Hevelius – via Encyclopedia Brittanica

Historian of astronomy Albert Van Helden explains:

In Selenographia he presented engravings of every conceivable phase of the Moon as well as three large plates of the full Moon: one of the ways the full Moon actually appeared through the telescope, one the way a maker of terrestrial maps might represent it (using the conventions of geographers), and one a composite map of all lunar features illuminated (impossibly) from the same side.[2]

 

MPC1-vintage-map-moon

Hevelius’ lunar map  influences astronomy, cartography, and navigation to this day by introducing us to longitudinal lines, necessary during the Age of Discovery when navigators had to figure out the difference between their local time and a distant reference point (the moon). They needed “a composite view that pictured the Moon in a way it never appeared in reality but was accurate in its placement of individual features,” Van Helden writes.[3]

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Selenographia. Observations of the Moon.

Did you know?

A large crater on the western edge of the Ocean of Storms is named after Hevelius?

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Hevelius Crater – NASA

 

Editor Note: If you enjoyed this Cartography post, check out the first in the series, Cartography and World Building.   Let me know what else you’d like to see…

[1] https://www.greekmythology.com/Titans/Selene/selene.html

[2] https://cnx.org/contents/t7AGYlN-@4/The-Moon

[3] https://cnx.org/contents/t7AGYlN-@4/The-Moon