Differential measurement of atmospheric refraction with a telescope with double fields of view

TL;DR

This paper introduces a novel differential measurement method using a double field of view telescope to accurately measure atmospheric refraction at low angles of elevation, demonstrated through experimental observations and prototype development.

Contribution

It proposes a new differential measurement approach with a double field of view telescope for atmospheric refraction at low elevation angles, validated by experimental results.

Findings

Measured atmospheric refraction at 78.8° zenith distance: 240.23" ± 0.27"

Feasibility of differential measurement method confirmed

Prototype limitations identified for future improvements

Abstract

For the sake of complete theoretical research of atmospheric refraction, the atmospheric refraction under the condition of lower angles of elevation is still worthy to be analyzed and explored. In some engineering applications, the objects with larger zenith distance must be observed sometimes. Carrying out observational research of the atmospheric refraction at lower angles of elevation has an important significance. It has been considered difficult to measure the atmospheric refraction at lower angles of elevation. A new idea for determining atmospheric refraction by utilizing differential measurement with double fields of view is proposed. Taking the observational principle of HIPPARCOS satellite as a reference, a schematic prototype with double fields of view was developed. In August of 2013, experimental observations were carried out and the atmospheric refractions at lower angles of elevation can be obtained by the schematic prototype. The measured value of the atmospheric refraction at the zenith distance of 78.8 degree is $240.23"\pm0.27"$, and the feasibility of differential measurement of atmospheric refraction with double fields of view was justified. The limitations of the schematic prototype such as inadequate ability of gathering light, lack of accurate meteorological data recording and lower automatic level of observation and data processing were also pointed out, which need to be improved in subsequent work.