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Bob,

Gary replied before I could. But in reality, the formula for computing the delta Ho correction is trivial and perfect for the simple cheap scientific calculators we generally talk about. You only need something with the cosine function.  Gary did the work by calculating the delta Ho's for knots 1 to ?? perhaps 12 but with this simple formula, you have every speed, time and relative Zn bearing possible. From Kaplan's paper, it is: 

delta Ho - correction (in minutes) added or subtracted from Ho or Hc to advance or retard the LOP to the 't' time specified. Essentially you are computing a new circle of position (larger if you your course is away, smaller if towards the GP).

s - speed in knots

t - time in minutes

Zn - azimuth to body in degrees

C - course in degrees

Zn-C is the relative bearing. If you look in HO249 inside cover (ignore the high speeds like 500 knots) each table row for the 4 min table has two Rel.Zn bearings. One is clockwise the other is counter clockwise and both produce the same result.

Once I saw how this worked, I couldn't believe I had not heard of this sooner. It is so slick and virtually eliminated the need to to graphic advances or retards of LOP to have common times to find a running fix.

I appreciate Gary's having brought MOO up.  And then there is motion of the body (MOB) that that's yet another topic.

Try this on some plots you have already done and see if you get the same result using MOO that you got with advancing/retarding LOPs.

Ed