RE: Laser arrow, 91vrdf video
=SUM(60*(2/((1/FComing)+(1/FGoing))))
Here is the Excel spreadsheet formula I wrote with information from HighPlains awhile back.
Frequency coming is the difference in frequency between two lines at the top and and FGoing is the difference in frequency of the same two lines at the bottom. I usually do it accross 5 lines and then divide by 5 for a better resolution. You need the program to do this.