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Originally Posted by Mav87th
When you write 47.5*N is that 47*5'N or 47*50'N ? I assume the later
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Yes, sry, I meant 47°50'N
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Originally Posted by don1reed
1)Those SR/SS tables, both van's and IRL are in "LOCAL TIME". Its up to the mariner to compute UT (GMT).
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Am I missing something again ? Van's SR/SS Almanac gives no Information about the longitude for any specific SR time. So it's the local time of what local point ? The only thing these SR/SS times can refer to is the GMT or am I wrong there ?
As I wrote in my previous post, the last time I tried to calculate my longitude I just used the time difference between the SR time from the almanac and the time my red light got turned off. At that moment I read the time from the upper clock, the one that pops up when you point with the cursor at the clock.
This difference was about ~1.3 hours (it was 9:10, the SR from the almanac read 7:49). And that calculated into my longitude ~20°W which was correct.
So I have the theory:
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Originally Posted by don1reed
3) I found out yesterday, while sailing NW in U.47 (AP 55° N, 7° 31' E), that the lower (white background) clock in SH3 dropped back one hour when the boat crossed meridian 7° 30' E, the boundary line between Prime Meridian 000° and 015° east.
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That this doesn't matter for the SR/SS times you get from the almanac if you use the points of "redlight on/off". This seems to be exactly the time when the sun sticks half out of the water and maybe just that little time difference to local time to even out the effect that the local time switches not at 15°W/E, 30°W/E, ... but at 7°50'W/E, 22,5°50'W/E, ...
I will test that for some different longitudes this evening to see if it fits then too as it did yesterday.