My students get 20 lashes of a wet noodle for failure to give the dimensions of each numeric in the calculation. The numbers are meaningless if we do not know the dimension they are specifying. If we assume a different one from the originators unspecified intent, we get ridiculous results. In my lab procedure manuals, I insist that each simplified calculation coefficient be accompanied by a full expansion of all of the factors and their dimensions that it is derived from. Rob has given us an excellent example of the confusion resulting from assuming rather than specifying explicitly the dimensions. Rod Willard >Ted Molczan correctly wrote that the maximum length of the tether could be > 360 * 4 / (2 * PI * 1019) = 0.225 deg >When I put 550 >in the above equation I get my earlier spurious value!!! The other >calculations were done using kilometers for ALL distances! >Apologies, Rob McNaught >rmn@aaocbn2.aao.gov.au