zOwie Omega Discussion Forum

My first question when you say your watch gains 2.5 seconds per 30 days is, how do you know that?

I've been tracking my 2254.50 (same movement as yours) for almost two months now, checking it against the USNO atomic clock at 3 specific points in the day.

It's rolling average is now +0.93 seconds/day. But it's not apples-to-apples if I compare that to a single 24-hour period. On that basis, my watch averages between +0.25 and +1.75 seconds per day, now -- and even that depends upon the time of day compared. I also see "lows" of -0.25 sometimes, and "highs" of +2.25 or thereabouts. (Because I was more or less active? outside or in more? ...a fraction of a second is a bit tight for me to claim much certainty in saying!)

Don't take my Seamaster off much (both for my own reasons, and now out of respect for Seismic Sam), but when I do, I always rest it in the 9-13 COSC test position (face up). So far, that's when it gains ~ 4.0 to 6.0 seconds/day. I haven't done much controlled analysis of this, but I would think that w/in a certain movement class, the same watch orientation would give the same time keeping variability; eg, face up, gain versus base readings (altho perhaps differing as to how much).

As temperature is also a consideration in COSC testing, I would also think that might be a factor in off-wrist versus on-wrist accuracy, in addition to orientation.