Daytime Seeing and Solar Limb Positions

TL;DR

This paper introduces a novel method for measuring atmospheric seeing during solar transits by analyzing the temporal dispersion of limb contact times with a grid, supported by numerical calculations and observational data.

Contribution

It proposes a new technique to quantify atmospheric seeing from drift-scan solar observations using grid contact timing and Fourier analysis.

Findings

Seeing affects the timing of solar limb contacts during drift scans.

Asymmetry in seeing effects at the start and end of transits is observed.

The method is validated with data from observatories in Locarno and Paris.

Abstract

A method to measure the seeing from video made during drift-scan solar transits is proposed. The limb of the Sun is projected over a regular grid evenly spaced. The temporal dispersion of the time intervals among the contacts between solar limb and grid's rows is proportional to the atmospheric seeing. Seeing effects on the position of the inflexion point of the limb's luminosity profile are calculated numerically with Fast Fourier Transform. Observational examples from Locarno and Paris Observatories are presented to show the asymmetric contributions of the seeing at the beginning and the end of each drift-scan transit.