OP - Thanks for this great essay. I enjoyed reading it.
OP - Thanks for this great essay. I enjoyed reading it.
Very interesting read. 24-hour watches definitely have their appeal.
I have a couple of questions though (not necessarily directed to the OP, feel free to answer):
1. (I'm assuming you own both 24- and 12-hour watches) Do you find it confusing to switch back and forth? Or do you only stick to 24-hour watches?
2. Can you give your opinion on these Russian watches? The first one (black Aviator) looks great. Any opinions on its movement/quality?
1 - For me it is not confusing maybe because here where i live we are used to a 24h scale (radio, tv, newspapers etc). For me it makes more sense a 24h scale watch because the day has...24h!
I also work in shifts so it makes even more sense to me. I also own 12h scale watches and i don't find it difficult when i switch from one to the other.
2 - I own one of those black PVD Aviator watches. It is very sturdy. Daily rate is around -10s to -15s a day. Movement is the hand wound Poljot 2623. From the official homepage they now use the hand wound Plojot 2614. Difference should be minor (try looking at the Russion forum for more info on these movements).
I hope this helps!
My "babies" My "babies" My "babies" My incoming "babies" My future "babies" Lüm-Tec B4 #13/100 YES WorldWatchII 24H Bezel W400.4 Alpha Watch PNR6-24H-Black Dial Seiko Spring Drive GMT SNR009 AirNautic Classic 24 (PVD) Aviator 24H (Volmax) 2623/1225830 Glycine Airman 2000 3764.19T66-MB AirNautic Early Bird (PVD) #8/50 Aviator 24H Black (Volmax) 2623/1224830 Parnis PVD 44mm GMT II AirNautic AN-24 Pilot "Raketa" 24H Submarine U100 Perpetual Watch Chronograph C-06 Steinhart GMT Ocean1 Black Citizen EcoDrive Calibre 8700 BL8000-54L Perpetual Watch GMT G-02 Tissot PSR516 Automatic T91.1.483.51 Seagull 819.351 WUS Chinese Moonphase 2011SE #72/150
Cybertrancer - Thanks for your reply. I will do some further research in the 24-Hour/Russian Fora :)
I had 1 Russian (can't remember which) that I sent back because it didn't seem very rugged. Many like them and they are certainly less expensive than a Glycine.
Good essay! I did order Russian 24-hour dial watch few days ago so this is theme forum is usable for me now.
These 24-hour dial watches are useful as a compass, when the Sun or shadows are visible! For example if 24-index is on the top, you can turn your watch so that a hour hand is pointing toward sun. Then the north is in direction of 24, south is in direction 12 etc. Daylight saving time affects this by one hour and you can correct this by remembering that the sun time is one hour less.
Of course you can use ordinary 12-hour watch similar way, but it is more complex (you can check for example a manual of a Seiko Alpinist). I have used a watch and the Sun as a compass several times. For example if you are travelling and you come out of a subway station, you must know a direction of the north before you can read a map. Using watch and sun is usually quick way to find those directions.
Last edited by cooma; June 8th, 2014 at 14:34.
I have used a watch as a compass sometimes in the way described above. 24-hour watches are very easy to use in this purpose. However I was wondering how accurate this method actually is, so I decided to calculate it. Besides I have never used a math program Octave and this was a good excuse to try it.
A direction of a shadow can be described as a local projection on the surface of the Earth. The local surface is a plane defined by unit vectors:
(explained for example here: Spherical coordinate system - Wikipedia, the free encyclopedia)
I choosed a coordinate system so that the Sun is shining to the direction of x-axis and the z-axis is perpendicular to the plane where the Earth is moving around the Sun. The axial tilt of the Earth is 23.5 degrees and the tilt looks like it rotates around z-axis in the choosed coordinate system. I used rotation matrices Ry and Rz (described here: Rotation matrix - Wikipedia, the free encyclopedia) to simulate it.
And now to the results. I calculated an error angle from the real compass direction. Basically "a watch compass" works better near to poles than near to the equator. At latitude 60 degrees where I live it works pretty fine (0 degrees in equator and 90 degrees in the north pole):
The biggest error lies in summer time. The middle point is in a summer.
This is a closer look at the daily variation in winter, when day light time is quite short:
The same in a summer time, when daylight time is quite long:
The above 15 degrees error is certainly tolerable. Compare to the common 12-hour dial where the angle between hour indexes is 30 degrees.
In the nearer to the equator in a latitude 30 degrees the error is bigger. It is still usable as a rough approximation for example to set a map in right position before reading it. I quess that bigger error in summer is caused by the Sun is even higher in noon and the shadows are very short:
In a "winter" time:
In a "summer" time:
In above pictures curves is drawed only when the Sun is visible. In a north, for example in latitude 60 degrees, the Sun is shining almost over night in a mid summer, so it is more usable then.
There is couple more small error sources besides the axial tilt angle and the latitude. The Sun time is max 15 minutes different to a local time because of the orbit of the Earth is elliptical which is equal to a max 7.5 degrees error. Also the local time zone is divided in one hour resolution which is equal to a max 15 degrees error. So this method is usually accurate enough for certain purposes.
Last edited by cooma; 1 Week Ago at 22:00. Reason: changed pictures drawed only in daylight time
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