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

TL;DR

This paper introduces a simple, citizen-friendly method for measuring the geocentric lunar distance using digital images, enabling amateurs to participate in astronomical measurements with minimal equipment.

Contribution

It presents a novel, accessible approach for non-scientists to measure lunar distance accurately using common digital devices and citizen science campaigns.

Findings

Achieved 3% precision in lunar distance measurement

Demonstrated feasibility of using smartphones and digital cameras for astronomical measurements

Engaged the public in scientific data collection and analysis

Abstract

We present the results of measuring the geocentric lunar distance using what we propose is the simplest method to achieve a precise result. Although lunar distance has been systematically measured to a precision of few millimeters using powerful lasers and retroreflectors installed on the moon by the Apollo missions, the method devised and applied here can be readily used by nonscientist citizens (e.g. amateur astronomers or students) and it requires only a good digital camera. After launching a citizen science project called the Aristarchus Campaign, intended to involve astronomy enthusiasts in scientific measurement of the Lunar Eclipse of 15 April 2014, we compiled and measured a series of pictures obtained by one of us (J.C. Figueroa). These measurements allowed us to estimate the lunar distance to a precision of 3%. We describe here how to perform the measurements and the method to calculate from them the geocentric lunar distance using only the pictures time stamps and a precise measurement of the instantaneous lunar apparent diameter. Our aim here is not to provide any improved measurement of a well-known astronomical quantity, but rather to demonstrate how the public could be engaged in scientific endeavors and how using simple instrumentation and readily available technological devices such as smartphones and digital cameras, any person can measure the local Universe as ancient astronomers did.