Atmospheric
This surface is used to simulate the effects of refraction through the Earth's atmosphere when viewing a star or point source. The atmosphere has a small but non-zero dispersion which introduces a tilt term to the incoming wavefront which depends upon wavelength. OpticStudio uses a model based upon those described in the following publications:
P. K. Seidelmann, Ed., "Refraction - Numerical Integration", Section 3.281, Explanatory Supplement to the Astronomical Almanac, pp. 141-143, University Science Books, Mill Valley, 1992.
C. Y. Hohenkerk and A. T. Sinclair, NAO Technical Note 63, Royal Greenwich Observatory Science and Engineering Research Council, 1985.
Six parameters are supplied to the model: The observed zenith angle of the source in degrees, the height of the observer above sea level in meters, the ambient temperature at the observer in Kelvin, the atmospheric pressure at the observer in millibars, the relative humidity (a number between 0.0 and 1.0), and the latitude of the observer in degrees.
OpticStudio computes the atmospheric refraction angle in radians for all defined wavelengths, then subtracts from all wavelengths the amount of refraction at the primary wavelength; thereby using the primary wavelength as a reference. To disable the referencing to the primary wavelength, set the "Absolute ?" flag to 1. Atmospheric refraction manifests itself as a small tilt in the OPD fan plot, or a slight chief ray offset similar to lateral color in the ray fan plot. All refraction is assumed to occur in the y direction only.
This surface models color separation. To model atmospheric turbulence, use the Grid Phase surface with an externally provided data file. For information on the Grid Phase surface, see " Grid Phase ".
PARAMETER DEFINITIONS FOR ATMOSPHERIC REFRACTION SURFACES
| Parameter # | Definition |
| 1 | Zenith |
| 2 | Height |
| 3 | Temperature |
| 4 | Pressure |
| 5 | Humidity |
| 6 | Latitude |
| 7 | Absolute |
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