official sunset/sunrise

[PK]

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

[Darryl Ramm]

On Apr 19, 9:05*am, 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

SeeYou Mobile displays sunrise and sunset on one of the stats pages.

There are various (free) sunrise/sunset calculators for the iPhone and
probably other platforms.

The US Naval observatory will generate tables you can print out if you
need an "official" time.

Darryl

[Wayne]

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.

Wayne
http://www.soaridaho.com

[Mike the Strike]

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

[Darryl Ramm]

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

[MickiMinner]

I can't tell how important that "sunset" time really is. I HATE
having a long flight not be counted because of 2 or 3 minutes! Judy
(The badge Lady) is very precise in her checking of the sunset times.
Please don't fall in that trap. I had a pilot in Logan Region 9 North
in 2009 that stayed out and out and out...and finally landed 2 minutes
before official sunset...WHEW!!!!!!!

[toad]

On Apr 19, 4:54*pm, MickiMinner > wrote:
> I can't tell how important that "sunset" time really is. *I HATE
> having a long flight not be counted because of 2 or 3 minutes! *Judy
> (The badge Lady) is very precise in her checking of the sunset times.
> Please don't fall in that trap. *I had a pilot in Logan Region 9 North
> in 2009 that stayed out and out and out...and finally landed 2 minutes
> before official sunset...WHEW!!!!!!!

I had a 1000km flight at Mifflin that I had to abort because of the
approaching sunset. I was comparing SeeYou Mobiles sunset with my
expected finish time and just did not have time to make the last
turnpoint ( just south of the wall ) and then return to Mifflin before
dark.

I still was able to claim a 750km flight ( out of 950km flown )
because I landed before sunset. And I didn't have to fly the Raystown
resevoir in the dark !!!

Todd

[Brian Whatcott]

Darryl Ramm wrote:
> /snip/
>> 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/snip/
>> 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 /snip/
> Darryl

I have run into a definition of sunset that used to go like this:
"The time at which the trajectory of the Solar center is six degrees
below the local horizon."

You can see how this could vary when the horizon is the Rockies, versus
five miles West where it might be 5000 ft lower...

Brian W

[Darryl Ramm]

On Apr 19, 8:14*pm, brian whatcott > wrote:
> Darryl Ramm wrote:
> > /snip/
> >> 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/snip/
> >> 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 */snip/
> > Darryl
>
> I have run into a definition of sunset that used to go like this:
> "The time at which the trajectory of the Solar center is six degrees
> below the local horizon."
>
> You can see how this could vary when the horizon is the Rockies, versus
> five miles West where it might be 5000 ft lower...
>
> Brian W

Stop tying to make this hard, there is one proper definition to worry
about for gliding in the USA. That is the table generated by the US
Naval Observatory. The FARs define sunset times as published in the
Air Alamanac which is produced by the US Naval Observatory, but for
practical purposes the official data is the USNO tables I provided the
link to. Those tables are exactly what is used for badge and records
flights in the USA and are the numbers glider pilots need to worry
about (unless the glider is one of the few equipped with lights and
appropriate certification, etc. to fly until the end of civil
twilight, in which case the USNO has civil twilight tables as well).

Darryl

[Brian Whatcott]

Darryl Ramm wrote:
> /snip/
>> You can see how this could vary when the horizon is the Rockies, versus
>> five miles West where it might be 5000 ft lower...
>>
>> Brian W
>
> Stop tying to make this hard, there is one proper definition to worry
> about for gliding in the USA. That is the table generated by the US
> Naval Observatory. The FARs define sunset times as published in the
> Air Alamanac which is produced by the US Naval Observatory, but for
> practical purposes the official data is the USNO tables /snip/
> Darryl

I have no problem with competitive sporting endeavors adopting a uniform
definition of anything they choose to. But supposing that the
Official Definition of Sunset from the USNO and the ACTUAL sunset time,
as described by the USNO, always coincide for a particular place and
time would be an over simplification.

At times, a LETHAL over-simplification.

Take this NTSB accident investigation from April 15th, 2002 for example.

<http://www.ntsb.gov/recs/letters/2002/A02_08.pdf>

Here an aircraft landing in the Rockies failed to note an intervening
summit. It was subject to a LOCAL sunset that was 25 minutes earlier
than the official sunset time as pointed out by the USNO in a footnote,
mentioned in this report.

Brian W

[Darryl Ramm]

On Apr 19, 9:05*pm, brian whatcott > wrote:
> Darryl Ramm wrote:
> > * /snip/
> >> You can see how this could vary when the horizon is the Rockies, versus
> >> five miles West where it might be 5000 ft lower...
>
> >> Brian W
>
> > Stop tying to make this hard, there is one proper definition to worry
> > about for gliding in the USA. That is the table generated by the US
> > Naval Observatory. The FARs *define sunset times as published in the
> > Air Alamanac which is produced by the US Naval Observatory, but for
> > practical purposes the official data is the USNO tables /snip/
> > Darryl
>
> I have no problem with competitive sporting endeavors adopting a uniform
> definition of anything they choose to. * * But supposing that the
> Official Definition of Sunset from the USNO and the ACTUAL sunset time,
> as described by the USNO, always coincide for a particular place and
> time would be an over simplification.
>
> At times, a LETHAL over-simplification.
>
> Take this NTSB accident investigation from April 15th, 2002 for example.
>
> <http://www.ntsb.gov/recs/letters/2002/A02_08.pdf>
>
> Here an aircraft landing in the Rockies failed to note an intervening
> summit. It was subject to a LOCAL sunset that was 25 minutes earlier
> than the official sunset time as pointed out by the USNO in a footnote,
> mentioned in this report.
>
> Brian W

Again the OP was a question about official sunset times. The official
definition of Sunset by the USNO is what they use to generate the
table. There is no conflict between USNO definition and their own
tables, do you really think there would be? This is not an arbitrary
SSA sporting definition, the SSA is ensuring glider badge and record
flights comply with the strict sunset flight requirements described in
the FARs (unless you can show you are legal to fly to civil twilight).

USNO Definition: "Sunrise and sunset. For computational purposes,
sunrise or sunset is defined to occur when the geometric zenith
distance of center of the Sun is 90.8333 degrees. That is, the center
of the Sun is geometrically 50 arcminutes below a horizontal plane.
For an observer at sea level with a level, unobstructed horizon, under
average atmospheric conditions, the upper limb of the Sun will then
appear to be tangent to the horizon. The 50-arcminute geometric
depression of the Sun's center used for the computations is obtained
by adding the average apparent radius of the Sun (16 arcminutes) to
the [So presumably by incorporation via the Air Almanac reference,
this is pretty much the technical description of Sunset referred to in
the FARs]

I hope pilots get this is a numerical model, they should especially
when presented with a relatively crude table. They need to take into
effect local conditions that affect safety, whether it be terrain,
weather etc. that can all affect local light. But again that was not
the question being asked, which was about official sunset times.

Darryl

[Brian Whatcott]

Stephen! wrote:
> brian whatcott > wrote in news:6
> :
>
>> I have run into a definition of sunset that used to go like this:
>> "The time at which the trajectory of the Solar center is six degrees
>> below the local horizon."
>>
>> You can see how this could vary when the horizon is the Rockies, versus
>> five miles West where it might be 5000 ft lower...
>
>
> Using that logic one could say that sunset occurs at 1500 when you are on
> the west side of a deep north/south canyon... After all, you can't see the
> sun anymore when it goes behind the mountain. It must be sunset, no?
>
> The horizon is the horizon, regardless of the local topography.
>

Not only could I say that actual sunset might be premature into a high
Rockies field, but more importantly, an accident investigation board
could say that, with backing from a USNO spokesman for that particular
accident site in the Rockies. But as someone has pointed out, an
official FAR night definition which is good for most times and most
places is a different proposition than the odd exceptional cases which
contribute at times to getting pilots killed.

Brian W
p.s. that old definition I (mis)quoted was apparently intended as a
definition for NIGHT rather than sunset, apparently.