Measurements of Tilt Anisoplanatism at the Firepond Facility
Abstract
Tilt anisoplanatism is the atmosphere-induced differential tilt seen by a common telescope observing two light sources separated by a very small angle. This report summarizes the results of tilt anisoplanatism measurements made at the Firepond Facility in Westford, Massachusetts. Two very precise visible quad trackers were used to simultaneously track each component of selected binary stars whose angular separations were in the range of 47 to 107 microrad. While the report describes the tracking hardware and its characterization, the major contribution of this work is quantifying the tilt anisoplanatism under a variety of seeing conditions. The measurements showed that the magnitude of tilt anisoplanatism can be on the order of 1 microrad rms for a 1.2-m telescope, a value several times larger than previously believed. The frequency distribution of the differential tilt is extremely variable, but most of the jitter strength lies below 30 Hz, with almost negligible contributions above 100 Hz. Calculations of the tilt anisoplanatism magnitude were made using the SLC and Hufnagel-Valley turbulence models. The calculations are in general agreement with the measurements, but accurate predictions require precise atmospheric measurements as inputs to the models. Keywords; Tilt anisoplanatism; Quad trackers; Binary stars; Atmospheric measurements; Frequency distribution; Jitter.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 18, 1988
- Accession Number
- ADA202681
Entities
People
- J. A. Daley Jr.
- J. J. Alves
- M. D. Zimmerman
- R. N. Capes Jr.
- R. Teoste
Organizations
- Massachusetts Institute of Technology