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Discussion Starter · #1 · (Edited)
Hi guys,
You may know sunset/sunrise beside storm notification was aksed by almost all the Ambit users from Suunto. Now Sunnto planned to add the features in Ambit2 and we hope to have it in Ambit classic as well. Here I will put information on how sunset/sunrise will claculated regarding to GPS information and local time. All hail to writer on Wiki.
Sunrise equation - Wikipedia, the free encyclopedia
May be a little complicated but if suunto adds some complex function like sunus (sin(X)) to movescount we may even write our own sunset/sunrise app.


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SUNSET/SUNRISE Equation:

The Earth rotates at an angular velocity of 15°/hour, therefore the expression
gives the interval of time before and after local solar noon that sunrise or sunset will occur.

The sign convention is typically that the observer latitude
is 0 at the Equator, positive for the Northern Hemisphere and negative for the Southern Hemisphere, and the solar declination
is 0 at the vernal and autumnal equinoxes when the sun is exactly above the Equator, positive during the Northern Hemisphere summer and negative during the Northern Hemisphere winter.

The expression above is always applicable for latitudes between the Arctic circle and Antarctic circle. North of the Arctic circle or south of the Antarctic circle, there is at least one day of the year with no sunrise or sunset. Formally, there is a sunrise or sunset when
during the Northern Hemisphere summer, and when
during the Northern Hemisphere winter. Out of these latitudes, it is either 24-hour daytime or 24-hour nighttime.



Generalized Equation


Also note that the above equation neglects the influence of atmospheric refraction (which lifts the solar disc by approximately 0.6° when it is on the horizon) and the non-zero angle subtended by the solar disc (about 0.5°). The times of the rising and the setting of the upper solar limb as given in astronomical almanacs correct for this by using the more general equation

with the altitude (a) of the center of the solar disc set to about −0.83° (or −50 arcminutes).



Complete calculation on Earth

The generalized equation relies on a number of other variables which need to be calculated before it can itself be calculated. These equations have the solar-earth constants substituted with angular constants expressed in degrees.


Calculate current Julian Cycle



where:

is the Julian Date;
is the longitude west (west is positive, east is negative) of the observer on the Earth;
is the Julian cycle since Jan 1st, 2000.[edit]Approximate Solar Noon

where:
is an approximation of solar noon at
.


Solar Mean Anomaly


where:
M is the solar Mean Anomaly.


Equation of Center


where:
C is the Equation of the center.

Ecliptic Longitude


where:
λ is the ecliptic longitude.


Solar Transit


where:
J[SUB]transit[/SUB] is the hour angle for solar transit (or solar noon).


Declination of the Sun


where:
δ is the declination of the sun.

Hour Angle


This is the equation from above with corrections for astronomical refraction and solar disc diameter.


where:
ω[SUB]o[/SUB] is the hour angle;
is the north latitude of the observer (north is positive, south is negative) on the Earth.
This is the main equation from above with the solar disc correction.
For observations on a sea horizon an elevation-of-observer correction, add
, or
to the -0.83° in the numerator's sine term. This corrects for both apparent dip and terrestrial refraction. For example, for an observer at 10,000 feet, add (-115°/60°) or about -1.92° to -0.83°.


Calculate Sunrise and Sunset



where:
J[SUB]set[/SUB] is the actual Julian Date of sunset;
J[SUB]rise[/SUB] is the actual Julian Date of sunrise.

Sunrise equation - Wikipedia, the free encyclopedia
 
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I sure hope Suunto just builds in the function as a regular watch features, so we don't have do all this math within the App Zone, and since Apps maybe are still only usable with Exercise Modes.
 

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I sure hope Suunto just builds in the function as a regular watch features, so we don't have do all this math within the App Zone, and since Apps maybe are still only usable with Exercise Modes.
It is my understanding after reading the published specs that the coming sunset/sunrise, storm alarm, and tidal data will be in the form pre installed apps created by Suunto.
 

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Discussion Starter · #8 ·

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This solar / lunar theory is working well however as others said seems like some geeky. :)

I started to thinking an app based on this theory. The first problem I faced with that app designer didn't know sin function. We can use basic math instead of like dev, mul and plus, so that's not a blocker.
The biggest problem is that there is no way to get GPS coordinates which is absolutely required for a sunset and sunrise app as you can see in the formulas above.

So, I hope that scoops are real and Suunto will develop an app or other solution for this problem as this feature for a hiker is a must have. That's why I don't wanna change my Core with an Ambit. Garmin Fenix would be a good option which offer solution for my other problems to which is web based apps like movescount.
To using this watch as a helpful device for a hiker it would be fine a good app which can support route creation. For that I need a topo map - with hiking routes and ways - what I cannot upload to movescount.

Now I'm waiting some month for Ambit2 or a new firmware and after decide to stay in Suunto family or move to Garmin.

Regards,
Marcell
 

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.... as this feature for a hiker is a must have.
Please, please someone tell why this is a must have? Sure, a bit of fun, but why a deal breaker? You head out into the hills knowing when the sun will rise and set. It doesn't change by that much each day. Local topography, vegetation and weather are going to have a much greater influence whether you run out of useful light on any given day.
 

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Please, please someone tell why this is a must have? Sure, a bit of fun, but why a deal breaker? You head out into the hills knowing when the sun will rise and set. It doesn't change by that much each day. Local topography, vegetation and weather are going to have a much greater influence whether you run out of useful light on any given day.
Hi.
I'll bite.

Sure, other than water not much is really a must have.
Sounds like you are agreeable to the importance of the knowledge of sunset times, but you just don't see need for it in a watch.

But if someone says they want to rely on it, then they probably need to rely on it. Or at least feel like they do. Maybe they aren't out everyday to be well calibrated, or they have poor night vision or got caught out in a sticky situation once because they mis-remembered, or maybe they are a werewolf or whatever. I guess the werewolves need the moonrise and phase function too.

Heck, today I wrote down it was the the 15th three times before I looked at a calendar and realized it was the 12th. So don't ignore that people have bad memories. And sometimes I'll work in the office to past dark everyday for a month and only have a vague notion that sunset is now 30-45-60min later than it was last time I saw one. Yep, pathetic. And yeah, not really be paying attention on weekends. But, indeed, I have survived this far in life only getting my first sunrise/sunset watch (a Core) a couple months ago.

And speaking of werewolves and moons, I really do like the moon phase/time implementation on the fenix. Really easy to scroll through the days ahead and see when I can go out. Not because I'm a werewolf, but just because a few times a year, it's nice to plan stuff around night light.
 

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Discussion Starter · #12 ·
Sunset/Sunrise is very important to me. I remmeber last year I made it to switzerland. I arrieved in Engelberg at night and I really want to see the sunrise in the morning. But while I arrived too late I was asleep in the morning.
I was only one day in Engelberg and I missed the sunrise.
 

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Hi.
In the spirit of Still Feeling Some Love for the Ambit 1, here's a new Sunrise Sunset App for the Ambit 1.
Yes, there is the Suunto app, but that gives a Countdown time remaining to the next Sun event and Not the usual "here are today's Sunrise and Sunset times."

There are other Ambit1 Sunrise/set apps, but all of those (I think) require you to modify and hardcode your timezone in the app.
My app allows you to chose one of three timezones relative to your current position by pressing the Lap button.
It's kind of crazy that Suunto doesn't give you acces to the UTC offset, which the watch *does* know. And without that all the User Apps forces these kinds of shenanigans. AFAIK how to figure out local sunrise times, anyways.

"Std" = Use when your location is within the standard 15-minute zone merdians and there is not Daylight Savings (e.g. Germany in the winter I think). Also use this if you are are West of the standard 15-minute zone and currently *is* DST, e.g. most of Spain in the summer (I think).
"DST/+1" = Use when you are within the standard 15-min zone and there *is* DST. Or one zone East and no DST.
"Std-1" = Use when your location is one 15-minute zone West of the standard time zone.

It seems to work well within a few minutes of the NOAA calculator for my location in recent weeks. NOAA now has a map-based tool to allow you to pick your *exact* location, which is cool.
Sunrise Set time graph.png

I think the theory on the equation I used is that it can have larger errors for some Latitudes and times of year...
But as I tested it for the past couple weeks, it's right in the mix with the NOAA, Ambit2 and Suunto App. Let me know if gives some kind of whacked out time for your location.

Sunrise Sunset Time of Day - App at Movescount.com
 

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Twilight Time

I always check the sunset time before going for my evening run. If I know that I can't make it back before sunset, I always bring along a torch light and/or reflector vest.

To those critics who say that the sunset time today is the same as the previous day, the problem is that I seldom keep track of the previous day's sunset time.

The sunrise/sunset feature of Ambit2 and countdown sunrise/sunset app of Ambit1, though are nice to have, are not precise enough for me.

I currently rely on an App on my mobile phone called Sunset Finder, which I find the Civil sunset time very useful & accurate. Before Civil sunset, there is still enough light to see eventhough the sun has set:
IMG_0255A.jpg


Here are some info on the Astronomical, Nautical & Civil Twilight time:

Educational - Twilight - WunderWiki

Twilight - Wikipedia, the free encyclopedia

AFAIK, no watches are able to indicate Twilight times. So, the question is, can some savy programmer here or even Suunto make an App that includes Twilight time?
 

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Re: Twilight Time

can some savy programmer here or even Suunto make an App that includes Twilight time?
Yes. Anyone who's bothered to get/make the equation for sunrise and set can modify it for whatever angle below the horizon they want. The interesting thing is I read is that angle is not necessarily some kind of universal definition... e.g. I think I read somewhere that Sweden at some point used a different angle. But that could have been for moon rise. or that it was the timing of the leading edge of the 'disc' vs the center of the 'disc.' I just know that I read something about Sweden being different somewhere once.

I have a hunch though that the offset for 99% of the earth's population is that 20-30minutes after sunset it's 'civilly' dark.

I'll have a re-look at my app to make a +/-6 degree 'civil' version. After I'm done with my EPOC and Bearing and Moon Phase and Moonrise (aka Lunar Madness App) and myriad other works in progress.
 

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Re: Twilight Time

AFAIK, no watches are able to indicate Twilight times. So, the question is, can some savy programmer here or even Suunto make an App that includes Twilight time?
getting close...

Ambit 2 sunrise
Watch sunrise.JPG

My app sunrise (DST)
My sunrise.JPG

Civil twilight app
Civil name.JPG

Civil twilight start (DST)
Civil time.JPG

timeanddate.com
- Sunrise = 7:49 am
- Civil Twilight = 7:18 am

still tweaking and validating it. Anyone want to buy me a ticket to Antarctica? Just kidding. I don't plan to make it gracefully handle polar regions.
 
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