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I think that the Zone in my example should have been 8 (not 9) since that
would give 12 36 for ZT LAN which would be later as expected than if the
observer was at 120 W long. See below...

example - say that you were at Longitude 127 degrees 30 minutes West and mer
pass is given as 1206.
You would solve as follows:
1)      convert the 127 deg. 30 minutes to time - (Hint: an easy way is to
divide by 15) This gives 8hours 30minutes in time.
2)      As you correctly stated you would ADD (because it is West long) the
8 hours 30 min in time to 1206. This gives you-
         20 36 UTC. For LAN at you longitude.
3)      If you want to express this UTC time of LAN in your local time, then
you need to subtract your Zone offset (i.e. the difference in whole hours
between your local time and UTC) - Say in this case that it is 8 hours
behind UTC, then you would take    20 36 - 08 00 = 12 36 ZT. for LAN.

4)      Note that if you were situated exactly on the central meridian of
your time zone e.g. at say 120 degrees W. Then the ZT of LAN would equal the
LMT of mer pass i.e. 1206. In this case. This is because you would take 1206
+ 0800 - 0800 which would give 12 06. In such a case, your watch if set to
local time would agree with the time given for mar pass on the daily page.

The confusing bit is that although we all keep the same local time within a
zone, two observers placed at each end of the  same zone (i.e. 15 degrees
apart) would experience LAN one hour apart in time although their watches
would read the same ZT.

Hope that helps
Ask further if you like...
Russell

   

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