Rule of 12ths and Sunlight
 

Peter Hendra wrote:

e.g. four fingers is one hour of daylight left. You can easily make a rough
estimate of the time until sunset this way. I know that one could look up tables
or even look up the page in the GPS that shows sunset at destination, but in mid
passage or when making landfall, it works well enough for me and is surpisingly
accurate. One could possibly get into arguments about degrees from the equator
but I don't care to go down that route.

Well, you might not want to, but I couldn't resist!

Using the following page:
http://aa.usno.navy.mil/data/docs/AltAz.html

I checked out the altitude of the Sun one hour before sunset at the
Equator and 60 North, for both Sept 20 and Jun 20.

At the equator, the altitude is about 13 degrees around the Solstice,
and 14.6 near the Equinox. And at 60 North its 4.7 and 6.7 degrees,
respectively. On July 30, at 45 North, its 9.6 degrees. So there's a
huge range here.

As for the angle subtended by the hand. My "eye to finger" distance
is 23 inches, and the four fingers are about 3 inches. This results
in an angle of about 7 degrees.

I know this is a bit geeky, but last year I was asked to figure out a
similar problem - the amount of time before sunset that the Sabbath
must be observed, as implied by the specifications in one of the Dead
Sea scrolls, as opposed to the normal Jewish Traditions. The DDS Cult
folks added an extra "Sun Diameter," or several minutes, depending on
time of year. They, like many others down through the ages, knew that
the End of the World was near, and if you wanted salvation, extra care
was needed to maintain purity.

Rule of 12ths and Sunlight
 

On Sat, 7 Oct 2006 08:20:13 -0400, "Glenn Ashmore"
wrote:

The big plus is that
everything but the electronics, spars, rigging and sails is on hand and paid
for so no more time wasted waiting for the boat kitty to refill. :-)

Don't under estimate the cost of spars, rigging and sails. I once
rerigged a Cal-34 from the deck up, and it was a big number even 20
years ago.

Rule of 12ths and Sunlight
 

On Sat, 7 Oct 2006 08:20:13 -0400, "Glenn Ashmore"
wrote:

Glenn, what's the latest estimate for splashing noises coming from
your direction?

.... The big plus is that
everything but the electronics, spars, rigging and sails is on hand and paid
for so no more time wasted waiting for the boat kitty to refill. :-)

I knew you had to be joking with that throw-away line:
ONLY the spars, sails, rigging, electronics?

Yowza!

Brian Whatcott Altus OK

Rule of 12ths and Sunlight
 

The strategy has always been to get the topsides, deck and interior all nice
and shiny looking and THEN invite the bank out for a cockpit party. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Brian Whatcott" wrote in message
...
On Sat, 7 Oct 2006 08:20:13 -0400, "Glenn Ashmore"
wrote:

Glenn, what's the latest estimate for splashing noises coming from
your direction?

.... The big plus is that
everything but the electronics, spars, rigging and sails is on hand and
paid
for so no more time wasted waiting for the boat kitty to refill. :-)

I knew you had to be joking with that throw-away line:
ONLY the spars, sails, rigging, electronics?

Yowza!

Brian Whatcott Altus OK