# CCD Field of View on the 18" Telescope

Diameter of the Telescope = 18 inches
Focal Length of the Telescope = 160 inches (157 inches according to Computer Aided Astrometry)
f/# = 8.888
Note: North is to the left and east is up on the FITS images.
In the case of CCD imaging one often talks about how much sky that fits in
one pixel. The image scale, w, can be expressed as:
w = 2F tan(d/2)
which can be approximated by:
w = (Fd)/k
Where
F = Focal length of the instrument
d = Angular size of the object
k = Proportionatility constant (k=206265 gives d in arc-seconds)
If we want to calculate the angular size of one pixel in the sky:
d = (w/F)*206265 , d in arc seconds
For the SFASU 18-inch using the Photometrics, Ltd. Star-1 camera, we have
F = 160 inches = 4.064 m
w = 23 micron square pixels = 23 X 10^-6 m
d = (23 X 10^-6)*206265/4.064 = 1.167 arcsec/pixel
Since the chip has 576 X 384 pixels, our FOV is
11.2 arcmin X 7.47 arcmin
**Parameters for Computer Aided Astrometry**
Focal Length = 3.9878 meters
Aperture = 0.4572 meters
23 by 23 microns