[amsat-bb] Re: Sun shadow for True North

[Dave Guimont]

>
>>A vertical rod about 4' long (plumb it, or use a level) will have the
>>shortest shadow at noon.

I should have said "near noon".....THE SH0RTEST 
SHADOW IS WHEN THE SUN IS DUE SOUTH OF YOU,NORTH 
IN YOUR CASE, No matter where you are with relation to the "clock"..

Check sunrise and sunset, divide by 2, add to the 
sunrise, and will give you THE TIME WHEN THE SUN 
IS HIGHEST....FORGET WHERE YOU ARE IN YOUR TIME ZONE....

That n/s line will be 90° to the e/w line made 
with the markers....You don't need a watch, or 
care where you are in the world....


>Not necessarily.  Ignoring DST, local solar noon 
>can occur anywhere within a window of around 1 
>hour (give or take, depending on the exact 
>borders of your local time zone), because each 
>time zone is approximately 15 degrees wide 
>(there are local variations that take the 
>official zones beyond the 15 degree nominal 
>zones).  For example, here in Melbourne, local 
>solar noon usually occurs around approximately 
>02:15 - 02:20 UTC (12:15 - 12:20 standard time 
>or 13:15 - 13:20 DST).  In Brisbane, it occurs 
>before noon AEST, despite both cities being in 
>the same time zone.  Using the "shortest shadow 
>at noon" method, you can have an error of up to 
>10 degrees (now THAT would ruin the performance 
>of your high gain antenna!).  Here, it would be 
>around 4-5 degrees, if one was ignorant of the actual time of solar noon.
>
>The moving shadow to find the East - West line 
>is a much better and MUCH more accurate idea.
>
>73 de VK3JED
>http://vkradio.com



            73, Dave, WB6LLO
                dguimon1 at san.rr.com

                    Disagree: I learn....

               Pulling for P3E...