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 Gary LaPook wrote:
>
> I get the calculated slope for Vega for the movement of the body (change in 
LHA) for the five minute period from 1628 to 1633 to be -58.6' doing the 
sight reduction and -58.35' by using the MOB table from H.O. 249. This table 
show -11.7' per minute of time at latitude 35� and azimuth 288� and -11.5' at 
latitude 35� and azimuth 290�. For latitude 30� the values are -12.4' and 
-12.2' respectively. Doing some simple interpolation makes the slope for the 
movement of the body -11.67' per minute of time and -58.35' for the 5 minute 
time period.

Yep, you're right.  There is another way to calculate it:
Delta H = 15 x cos latitude x sin azimuth
Where Delta H = rate of change in arc minute per minute of time

Using that formula (x5) gives - 58.3

> The adjustment for the movement of the ship is plus 1.1' minutes. If you use 
my table you can take the value for 7 knots and relative bearing of 20� 
(ZN-TR, 289-270 = 19, ~ 20) which is .5' and double it to find the correction 
to be + 1.0'. You can also do the same thing using the MOO table from H.O. 
249 which shows + 11.05' (interpolating) for 700 knots and relative bearing 
of 19�. Divide by 100 to get the adjustment for 7 knots, multiply by 2 to get 
it for 14 knots and then multiply by 5 minutes to get the adjustment of + 
1.1'.� (You get the same value using a calculator, 14 knots divided by 60 
minutes gives a ship movement of .23 NM per minute, times 5 minutes makes 
1.17 NM times the cosine of the relative bearing, 19�, makes the correction 
of + 1.1' also.)

Thanks for this explanation.  So applying this correction results in a
corrected slope of - 57.2 ?

   

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