Sunrise/sunset./Twilight/Moonrise/etc on a gps?

 

I was just pondering something I'd like to see on a GPS unit - Some basic "Astronomical" data - times for sunrise, moonrise, etc. There's also something called Civil Twilight and Astronomical Twilight. Civil twilight is generally the time it gets dark enough to NEED headlights when on the road, and astronomical twilight when its dark enough to start seeing a few stars, at least with a telescope.

Anyone know of a gps unit that calcuates such things?

Garmin...

The Garmin Rino Series of FRS/GPS systems have that information and much much more.

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The eTrex Legend HCx (and I would imagine the other units in the eTrex line) shows the times for sunrise, sunset, moonrise, and moonset each day. It doesn't have the civil twilight time, though.

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Magellan's hiking GPS units also show sun and moon rise/set times as well as the moon's current phase.

On their compass screens the current position of the sun and moon in the sky are displayed. (There is no civil twilight display).

It's strange that they don't add this simple feature to automotive dashboard GPS units.

eTrex yes, nuvi no

My plain yellow eTrex has that info, but my nüvi 200 does not.

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><> Glenn <>< Garmin nüvi 2598

There are three

skunkape wrote:

I was just pondering something I'd like to see on a GPS unit - Some basic "Astronomical" data - times for sunrise, moonrise, etc. There's also something called Civil Twilight and Astronomical Twilight. Civil twilight is generally the time it gets dark enough to NEED headlights when on the road, and astronomical twilight when its dark enough to start seeing a few stars, at least with a telescope.

Anyone know of a gps unit that calculates such things?

All these times are important to me as an astronomer, but I usually have the times in my head when I am heading to the telescope or are right in front of me when I'm working...

To answer your questions:

Sunrise/Sunset is the moment when the last rays of the sun would be visible on a flat horizon *IF* there was no atmosphere. (Atmospheric refraction can change the actual value by up to 5 minutes in either direction so you may see it before the predicted time or after...

Civil Twilight is defined when the Sun is 0 to 6 degrees below the horizon. Car lights should come on during this time and under a clear and open sky, you should still be able to read newsprint.

Nautical Twilight is when the Sun is 6 to 12 degrees below the horizon. On the sea, this is when it has gotten, or is still so dark that you can not differentiate the horizon between sea and sky.

Astronomical Twilight occurs when the Sun is between 12 - 18 degrees below the horizon. The end of Astronomical Twilight is when there is NO measurable light in the sky visible to you after sunset and the beginning of "A T" is when the sun starts to lighten the sky once again the next morning.

Of course all of these change depending on the date, your latitude and altitude. Since your GPSr 'knows' all of these things, the calculation is straightforward.

Calculation of the position of the moon in it's orbit to include moon rise/set & phase in the output is a bit more complicated, but as seen in other posts to this thread, is not uncommon in the hiking units. I suspect the reason all units don't carry them is most people driving their vehicles (or in general) don't really care about any of these things, while hikers have a much more pressing need to know at least sunrise/set, moonrise/set and the moon's phase.

My Nuvi 260 changes automatically from Day to Night mode & back again AT sunset/rise, so it is doing the calculation for this. I just haven't seen any way to display these times...

Hope that helps.

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Nuvi 2595LMT, Nuvi 1490T, Nuvi 260, GPSMAP 195

Forerunner 205

I have seen settings for sunrise and sunset on the Forerunner 205.

Cool

jwt873 wrote:

Magellan's hiking GPS units also show sun and moon rise/set times as well as the moon's current phase.

On their compass screens the current position of the sun and moon in the sky are displayed. (There is no civil twilight display).

It's strange that they don't add this simple feature to automotive dashboard GPS units.

COool - i'm glad to kmow there are some gps's that do this...and ya...i;m wondering why automotive GPSs dont seem to have this - be great for cross country driving...driving through different time zones...and latitutes/longitudes...(ive driven Pittsburgh To Los Angeles twice) and it would definatly be nice to have some idea how much daylight i have to drive in.

cool

rocknicehunter wrote:
skunkape wrote:

I was just pondering something I'd like to see on a GPS unit - Some basic "Astronomical" data - times for sunrise, moonrise, etc. There's also something called Civil Twilight and Astronomical Twilight. Civil twilight is generally the time it gets dark enough to NEED headlights when on the road, and astronomical twilight when its dark enough to start seeing a few stars, at least with a telescope.

Anyone know of a gps unit that calculates such things?

All these times are important to me as an astronomer, but I usually have the times in my head when I am heading to the telescope or are right in front of me when I'm working...

To answer your questions:

Sunrise/Sunset is the moment when the last rays of the sun would be visible on a flat horizon *IF* there was no atmosphere. (Atmospheric refraction can change the actual value by up to 5 minutes in either direction so you may see it before the predicted time or after...

Civil Twilight is defined when the Sun is 0 to 6 degrees below the horizon. Car lights should come on during this time and under a clear and open sky, you should still be able to read newsprint.

Nautical Twilight is when the Sun is 6 to 12 degrees below the horizon. On the sea, this is when it has gotten, or is still so dark that you can not differentiate the horizon between sea and sky.

Astronomical Twilight occurs when the Sun is between 12 - 18 degrees below the horizon. The end of Astronomical Twilight is when there is NO measurable light in the sky visible to you after sunset and the beginning of "A T" is when the sun starts to lighten the sky once again the next morning.

Of course all of these change depending on the date, your latitude and altitude. Since your GPSr 'knows' all of these things, the calculation is straightforward.

Calculation of the position of the moon in it's orbit to include moon rise/set & phase in the output is a bit more complicated, but as seen in other posts to this thread, is not uncommon in the hiking units. I suspect the reason all units don't carry them is most people driving their vehicles (or in general) don't really care about any of these things, while hikers have a much more pressing need to know at least sunrise/set, moonrise/set and the moon's phase.

My Nuvi 260 changes automatically from Day to Night mode & back again AT sunset/rise, so it is doing the calculation for this. I just haven't seen any way to display these times...

Hope that helps.

Thanks for the detailed info. To be honest I was aware of the technical details - i've written some calendar software, and researched this a little, so I know about the degree ranges, about geocentric vs topocentric coordinates, azimuth, elevation, ascension, spherical coordinates etc. And ya the Moon calculations are not that hard for even a slow computer to handle quickly. I didn't mention the more technical details cause i figured most people's eyes would glaze over.

I was more interested in units that had this kind of functionality.

Of course your post is here for those who want it i guess

skunkape wrote: I was just

skunkape wrote:

I was just pondering something I'd like to see on a GPS unit - Some basic "Astronomical" data - times for sunrise, moonrise, etc. There's also something called Civil Twilight and Astronomical Twilight. Civil twilight is generally the time it gets dark enough to NEED headlights when on the road, and astronomical twilight when its dark enough to start seeing a few stars, at least with a telescope.

Anyone know of a gps unit that calcuates such things?

I have a garmin IQue M5 and when I go to the menu tab I get an almanac that shows sunrise and sunset. Also shows good and poor hunting days.

Useful

I think this would be useful information; sunrise and set are already being computed and I doubt it'd be significant to add moon data too it.

I have to admit I always chuckle when Emily my C340 knows when it's sunset.

My eyes were glazed over too

skunkape wrote:

...
Thanks for the detailed info. To be honest I was aware of the technical details - i've written some calendar software, and researched this a little, so I know about the degree ranges, about geocentric vs topocentric coordinates, azimuth, elevation, ascension, spherical coordinates etc. And ya the Moon calculations are not that hard for even a slow computer to handle quickly. I didn't mention the more technical details cause i figured most people's eyes would glaze over.

I was more interested in units that had this kind of functionality.

Of course your post is here for those who want it i guess

Yep you are correct. That didn't really answer your question about which units have this feature.

Your not quite right statement about Astronomical Twilight caught my eye and I was bored waiting for breaks in the clouds last night so figured I'd give a more complete explanation for anyone who didn't know. Sorry to go a bit astray on the topic...

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Nuvi 2595LMT, Nuvi 1490T, Nuvi 260, GPSMAP 195

reerences

rocknicehunter wrote:
skunkape wrote:

...

Yep you are correct. That didn't really answer your question about which units have this feature.

Your not quite right statement about Astronomical Twilight caught my eye and I was bored waiting for breaks in the clouds last night so figured I'd give a more complete explanation for anyone who didn't know. Sorry to go a bit astray on the topic...

That's cool - im sure the info is useful for those who are interested. ANd I guess i was a little off on astromonical twilight - not being much on astronomy - the exact definition escaped me when i wrote the post.. SOrry smile

If any o you guys want a really good explanation of this stuff - my personal recommendation would be to check out the reference docs for Turbo Power System Tools (open source), a delphi language library for a number of things - including calculating sunrise, sunset, position of sun and moon in the sky, etc. They do a agreat job of explaining the basic concepts.

http://sourceforge.net/project/showfiles.php?group_id=71011

If you guys are really brave, check out the "Explanitory Suplement to the Astronimical Almanac" y P. Kenneth Seidelmann - a more mathematical explanation on all this stuff. If memory serves me right, this is published by the U.S. Naval Observatory, the guys that run the governemnts Atomic Clocks.

ZZZZZZZ

skunkape wrote:

...

If you guys are really brave, check out the "Explanitory Suplement to the Astronimical Almanac" y P. Kenneth Seidelmann - a more mathematical explanation on all this stuff. If memory serves me right, this is published by the U.S. Naval Observatory, the guys that run the governemnts Atomic Clocks.

Talk about glazing eyes... I need to stay up at night. The last thing I want to do is read that!!

And no need to apologize. My first post was actually off query if not off topic.

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Nuvi 2595LMT, Nuvi 1490T, Nuvi 260, GPSMAP 195

cool

mikeal wrote:

I have a garmin IQue M5 and when I go to the menu tab I get an almanac that shows sunrise and sunset. Also shows good and poor hunting days.

Digging around Garmin's Mapsource program for windows, I discovered it calculates this stuff, but if the nuvi 760 does it, i sure can't find it. Anyway, at least I can have it on my laptop if i'm driving long distance