Measuring Danjon index and umbral magnitude of a partial lunar eclipse (July 16, 2019)

TL;DR

This paper measures the Danjon index and umbral magnitude during the partial lunar eclipse of July 16, 2019, using observational comparisons with planetary light and compares results with historical eclipse data.

Contribution

It introduces a method to estimate the Danjon index and umbral magnitude from observational data during a partial lunar eclipse.

Findings

Estimated Danjon index for the 2019 eclipse.

Compared lunar eclipse luminosity with planetary light.

Published data on previous total lunar eclipses.

Abstract

The partial lunar eclipse of July 16, 2019, left the lower part of the Moon illuminated at its maximum phase in Padova (Italy). Occulting it behind far buildings it was possible to compare the light of Jupiter and Saturn de-focused to the same diameter of the Moon with the light from the umbra. The luminosity of the eclipsed Moon as well as the Danjon index have been estimated and compared with ephemerides. January 21, 2019, July 27, 2019 and September 28, 2015 total lunar eclipses data are also published.