At 05:29 AM 12/29/2007, Dave Guimont wrote:
A vertical rod about 4' long (plumb it, or use a level) will have the shortest shadow at noon.
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
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".....
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@san.rr.com
Disagree: I learn....
Pulling for P3E...
Quite Right:
For example Alaskan Standard time was politically moved ahead (eastward) one time zone to be equal to Yukon Time and -1 hour from Pacific (PST) Time. But solar noon was 13:06:39 this afternoon (when the sun reached max elevation=6 degrees). I suggest one use NOVA or many of the other tracking programs to find when the sun crosses your local Meridian (i.e. is azimuth=180). Then the sun is exactly south! I have used that to spot whether my eme antennas were off. I could look at the tower shadow and align the antennas to be within a few degrees. My Ham-IV rotator has about 10-degrees accumulative error as I rotate clockwise 180 degrees. I had to make myself a lookup table to keep on the Moon.
I installed an old TV camcorder on the antennas to visually track the Moon, but it did not like the long video cable to the shack.
BTW we had 5:20:20 hours:min:sec of daylight today.
73 Ed - KL7UW
At 03:06 PM 12/28/2007, Tony Langdon wrote:
At 05:29 AM 12/29/2007, Dave Guimont wrote:
A vertical rod about 4' long (plumb it, or use a level) will have the shortest shadow at noon.
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
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73, Ed - KL7UW ====================================== BP40IQ 50-MHz - 10-GHz www.kl7uw.com 144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w DUBUS Magazine USA Rep dubususa@hotmail.com ======================================
At 01:47 PM 12/29/2007, Edward Cole wrote:
I installed an old TV camcorder on the antennas to visually track the Moon, but it did not like the long video cable to the shack.
A TV transmitter should do the trick... ;)
BTW we had 5:20:20 hours:min:sec of daylight today.
Eeeek! That would be drive me nuts... It's bad enough when we get down to 9:30 hours of daylight in winter. Currently, the sun peaks at 75 degrees above the horizon and we're getting around 14:30 hours of sunlight each day. :)
73 de VK3JED http://vkradio.com
participants (3)
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Dave Guimont -
Edward Cole -
Tony Langdon