On Wed, 26 Jun 2002, Terry Simpson wrote: > ... > Mirror image numerals are essential for using a compass with a mirror or > prism (which inverts the numbers). Are you aware of this?
Indeed, my 1918 Military Compass has a prism-lens combination which restores and magnifies the mirror-image numbers on a scale having least divisions of one degree. The other scale for direct viewing only has least divisions of five degrees. There is little chance of reading the wrong scale directly, or indirectly through the prism-lens. My previous statement on this matter was confusing. My fault. My later 1940s (?) Military Compass has only a simple lens for magnifying the numbers in mils on a scale of 20 mils least divisions (1.125 degrees) The same lens also magnifies the direct scale in degrees having least divisions of 5 degrees. This compass was made by W. & L. E. Gurley of Troy, N.Y., USA. Mechtly described: > >Two artillery observers, triangulating on a target, ... Terry replied: > Or more commonly: just one observer. How did you determine *range*, Terry, from one point of observation? Did you use a range finding laser device? Mechtly continued: > > The usual compensation for error is to fire several rounds for > > confirmation > > of target location, and then many rounds for destructive effect. > > Yes. I have done this with a prismatic compass. Terry, what are the particulars of a NATO (or UK) Military Compass. It appears to combine aspects of both the 1918 and Gurley compasses I have described above. Is there *only* a mil scale, or is there also a degree scale? What are the least divisions? Can both be read through the prism? Gene.
