# CCD Field of View on the 18" Telescope

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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

```