Filter and Aperture Wheels
The filter wheel and the aperture wheel each have 15 positions, one of
which is "dark" in each wheel. Aperture diameters range from 0.01" to
0.50", plus one "open" position (a 1" hole). Specific sizes and
projected values on the sky at the 42" f/8 are as follows (projected
aperture sizes are about 4x smaller at the 72"):
1 = 0.010 in diam 6.1"
2 = 0.020 in diam 12.1"
3 = 0.039 in diam 23.7"
4 = 0.062 in diam 37.6"
5 = 0.078 in diam 47.4"
6 = 0.100 in diam 60.7"
7 = 0.125 in diam 75.9"
8 = 0.156 in diam 94.7"
9 = 0.203 in diam 123.2"
10 = 0.250 in diam 151.8"
11 = 0.328 in diam 199.1"
12 = 0.400 in diam 242.8"
13 = 0.500 in diam 303.5"
14 = 1.000 in diam 607.1"
15 = DARK