Distortion at the Prime Focus of the Shane Telescope with the
Epps Atmospheric Dispersion Compensator
In 1994 June the Shane prime focus Atmospheric Dispersion Corrector
(ADC) was used to expose several plates. The plates were held in a
test rig intended to match the future position of the MOS plate.
Burt Jones produced a plate solution that included a radial polynomial
distortion. The text of his writeup is given below.
Minor rewriting has been done to replace subscripts and Greek letters
with TeX-like representations suitable for HTML2 WWW browsers.
P.F. Corrector Plate Distortions from Burt Jones
Set up standard coordinates x_t, y_t using
Then positions of stars in mm in Focal Plate will be
plate center as tangent point
refracted coordinates for field center and star positions
scale of 12.3230 "/mm
x = x_t + alpha * (x_t - x_0) * r^2 + beta * (x_t - x_0) * r^4
y = y_t + alpha * (y_t - y_0) * r^2 + beta * (y_t - y_0) * r^4
r^2 = (x_t - x_0)^2 + (y_t - y_0)^2
alpha = 4.489E-7 mm^-2
beta = 1.731E-12 mm^-4
x_0 = 6.399 mm
y_0 = -0.215 mm
Further discussion with Burt Jones suggests that some of this transformation
may not be suitable for use with the MOS. Some good references are
Murray, MNRAS 154, 429 (1971)
Herbig & Jones, AJ 86(8), 1232 (1981)
Back to the MOS home page.
Steve Allen <email@example.com>