We present the results of measuring the geocentric lunar distance using whatwe propose is the simplest method to achieve a precise result. Although lunardistance has been systematically measured to a precision of few millimetersusing powerful lasers and retroreflectors installed on the moon by the Apollomissions, the method devised and applied here can be readily used bynonscientist citizens (e.g. amateur astronomers or students) and it requiresonly a good digital camera. After launching a citizen science project calledthe Aristarchus Campaign, intended to involve astronomy enthusiasts inscientific measurement of the Lunar Eclipse of 15 April 2014, we compiled andmeasured a series of pictures obtained by one of us (J.C. Figueroa). Thesemeasurements allowed us to estimate the lunar distance to a precision of 3%. Wedescribe here how to perform the measurements and the method to calculate fromthem the geocentric lunar distance using only the pictures time stamps and aprecise measurement of the instantaneous lunar apparent diameter. Our aim hereis not to provide any improved measurement of a well-known astronomicalquantity, but rather to demonstrate how the public could be engaged inscientific endeavors and how using simple instrumentation and readily availabletechnological devices such as smartphones and digital cameras, any person canmeasure the local Universe as ancient astronomers did.

The simplest method to measure the geocentric lunar distance: a case of citizen science

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