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Precise solar limb measurement with your smartphone: the October 14 eclipse!

Presentation #110.14 in the session Data Analysis Techniques Posters.

Published onSep 18, 2023
Precise solar limb measurement with your smartphone: the October 14 eclipse!

Funded by a NASA HITS award, we are developing a new smartphone app that aims to achieve the most precise timing of the appearance/disappearance of the Diamond Ring/Baily’s Bead phenonena at an eclipse’s 2nd and 3rd contacts. The app will work on both IOS and Android platforms, will not require any special preparation. It will return its data to a NASA portal automatically. We intend to recruit as large a number as possible of citizen observers for the total eclipse, by circulating the app broadly and for free as a part of NASA’s eclipse organization for the April 8, 2024 total eclipse. Thanks to geolocation and precise timing of the observations from GPS at each smartphone, the data obtained from many points along the eclipse track will be used, in conjunction with the exquisitely-detailed lunar topography databases from NASA’s LRO and JAXA’s Kaguya missions, to define the solar limb precisely. How round is the Sun?

This app development takes advantage of experience in the 2017-2024 Eclipse Megamovie program ( and is based on software developed in 2017 at Ideum, coincidentally located in the path of the 2023 annular eclipse (October 14). The path links Eugene, OR, Albuquerque (NM), and San Antonio (TX) in the US. Although the new app is under development and will not be offered to the public at large, we would like SPD participants to help test it even though such an eclipse is of course not ideal for the science objectives. We plan for broad participation via NASA support in 2024.

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