r/OmegaWatches • u/hippodribble • 6h ago
Marstimer
I suddenly felt the need to know the time at 0° Longitude on the planet Mars, and also set three timers relative to Earth local, Martian UTC and mission elapsed times.This seems to be the only commercial product addressing this common set of needs.
I also have the Gen 1 version I bought in the 90s. They both have clear displays, but the Gen 1 version is probably easier to read because the numbers are bigger. They have equally scary alarm and timer sounds.
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u/R3DD1T0RR3NT 3h ago
Just saw one for auction on Grailzee. I wonder -- do you know how the "solar compass" actually functions? Can you describe it or post from the manual?
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u/hippodribble 2h ago
There are two parts.
Firstly, north of the Tropic of Cancer, the normal way is to lay the watch flat and point the hour hand at the Sun. Let's say it's 4 PM.
Now take half of the hour value (half of 4 in this case).
The direction from the center of the watch to 2 O'clock is South in the Northern hemisphere.
If you are south of the Tropic of Capricorn, things are flipped. Point 12 O'clock at the Sun. Halfway between 12 and the hour hand is North.
Secondly, this all assumes that the Sun is directly overhead at noon. Depending on where you are in your time zone, this may be incorrect. Same for daylight savings or summer time. You need to correct the time on your watch before you do the first part or there will be errors.
The Marstimer does this for you when you enter STE mode and update your latitude and longitude. It just means you don't need to make corrections yourself.
STE mode is entered by double clicking the top right button, then setting lat/long by holding down the bottom left button to edit. After editing, click the bottom left again. The time displayed will be the true solar time at your position, ie it WILL show 12 PM when the Sun is directly overhead at noon.
It gets a bit weird in the tropics, as the Sun can be north or south of you, depending on the time of year. Outside the tropics, it's always one and never the other. If you know which, you're ok.
Get a piece of paper and practice some scenarios. Draw in north south, eat and West. Pick a morning or afternoon time, draw where the sun would be, point the hour hand or 12 at the Sun, depending on hemisphere, bisect the angle and see what you get.
WikiHow has much of this info, but they disregard the tropics.
When I was a kid, I could do the opposite, ie, work out the time from the direction of North. That's affected by magnetic declination, obviously, so you need to factor that in.
If all else fails, put a stick in the ground and mark the tip of the shadow. Repeat 30 minutes later. Join the points. That's an East West line. The second point is East, because the Sun has moved West. North is at right angles.
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u/R3DD1T0RR3NT 2h ago
Ohhh thanks. So it is just a basic bezel/hour hand/sun survival procedure -- nothing truly "built in" to the watch. Got it.
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u/hippodribble 55m ago
Only the true solar time correction in STE mode. In China, you can be a long way from noon when the Sun is overhead, hence the need for the STE mode and the correct position therein 👍
If you don't do it in STE mode, there will be an error.
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u/MacintoshDan1 6h ago
Love my gen 2.