This is a variant on an experiment that I described a few years ago – https://heartontheleft.wordpress.com/2008/06/11/was-eratosthenes-correct-a-multi-class-science-project/

Source: The Great KENTUCKY Eclipse of August 21, 2017: Measuring the Moon’s Distance – The Catholic Astronomer