standard error in parallax measurement (in 
angular units), 
standard error in parallax measurement (in 
linear units), 
standard errors in pointing to targeted points 
on the negative (in angular units), 
standard error in pointing to targeted points on 
the negative (in linear units), and 
conversion factor between radians and arc-angular 
units. 
Obviously, 
(16) 
(17) 
It might be of interest to note that equations 10, 11, and 
12 differ slightly from the equations derived by Zeller (Baschlin 
and Zeller, 1934, pp. 209-222) for the same purpose, inasmuch as