On Apr 19, 11:48*am, Mike the Strike wrote:
On Apr 19, 10:24*am, Wayne wrote:



On Apr 19, 12:05*pm, PK wrote:

Since most of us that fly cross country (or locally as weel), and are
restrained by the FAR's to be on the ground before sunset *assuming
that we don't have position lights. Since most of us use some kind of
navigational devise (SeeYou, Glide Navigator, WinPilot etc.), I am
wondering if any of these programs utilize some data showing sunset at
the region one happens to be in? I am running WinPilot, and not aware
of of any data availabe in conjunction with it. What is everybode else
doing?? 6PK

My system is very crude. *I use a Garmin 12xl to drive a B50 which in
turn drives my PDA. *One of the 12xl screens displays official sunrise
and sunset for the current coordinates. *Switching 12xl screens does
not effect NMEA data or the PDA presentation. *So if I need the sunset
time, I simply select to the sunrise/sunset screen on the Garmin.

Waynehttp://www.soaridaho.com

One of the problems we've seen is that there is really no such thing
as an "official" sunset time, just times calculated from astronomical
tables based on a lat/long on the earth's surface. *Although these
agree with each other reasonably well, they use geometric
approximations of the earth's shape. *Even over sea, there is an
uncertainty of a minute or so over the time the sun actually sets
because of differences in atmospheric refraction. *In mountainous
country (like we are in Arizona), actual sunset time can differ from
that calculated in tables by many minutes. *This has led to some
grumbling when flights were disallowed because landing occurred after
a calculated sunset, but before an actually observed sunset.

Another wrinkle at our home field is that our prevailing winds have us
land to the west on our main runway and this is definitely easier and
safer just after sunset than just before it, when the setting sun
would be in your face. *Fortunately for us, mountains to our west
result in sunset at the field before the computed sunset for our
location, so folks looking at the "official" sunset time don't ding
us. *Presumably, though, we should still show position lights if we
land after the sun has actually set at our field.

Mike

It may be semantics but the problem some pilots run into is there is
*exactly* a precise definition of sunset time, it's just too bad it
might be different from what they observe because of what you mention.
Which is why I assume the OP is after a tool that gives pilots
"official times" (which for us in the USA are the US Naval Observatory
times -- i.e. Judy will look at http://aa.usno.navy.mil/data/docs/RS_OneDay..php
for your badge or record flight). SeeYou seems to be close (~1 minute)
to the naval observatory tables when I checked, I presume Garmin gets
this right. Hopefully everybody understands there is absolutely no
leeway on this, if you are outside the official sunset times by even a
small amount you are going to have problems with badges and records.


Darryl