Checking the current accuracy of my watch...

Hi guys.. Simple question here..

I have a 10 year old Sea Master 300m, never serviced (yet).. and wanted to see how it's doing. So, I started keeping track using the site time.is. I looked at my watch, unscrewed the crown and waited until the sweeping second hand stopped perfectly at "12" and stopped it. Then, set the time and waited for the exact moment the time.is site matched and pushed the crown in. I started a log, and wanted to see how it does for a week, and month etc.

So far, its been 3 days. I have made some interesting observations and want to ask..

In the first 24hrs it lost 5 seconds. This was me wearing the watch the whole time (just not in the shower). This means, I wore it to bed as well.

Then.. the next evening, I decided to lay it flat while overnight. This did in fact prevent too much more loss. In fact, by morning it had only lost 1 additional second. From there, I put the watch on.. and wore it until the next night. During the day around 3pm (when the test started) I took note, and it was now running -7sec for a full 48hrs. By that evening, it was -8sec. Again, took it off overnight resting face up.. and this morning it was the same, -8sec. Wore the watch now for a few hours and now has dropped another sec. (-9)

My point, and question is this..

I see that when I ware the watch all the time.. it looses time at a much faster rate. (well, thats probably not correct, it looses at the same rate.. but by keeping it face up at night it compensates by running faster). So, then when people say my watch is running "x" per day.. how are they suppose to measure this? For example, I plan to service the watch soon.. and I want to see a "before & after" in terms of performance. Do most people take their watch off at night? Should the watch not run any faster when face up? Again, I am not complaining at all.. (in fact so far its pretty impressive I think).. its 10 years old, with no service lol. I just want to know the basics on how this is calculated and how people are measuring the accuracy.

Thanks!

Travis

+/- 5 seconds a day seems ok to me!

I too use Time.is.

If you think about it, a watch's balance spring / wheel assembly has to deal with a lot. When you are wearing it during the day, turning your wrist in all sorts of directions, it is acted upon by the earth's gravity plus any movement of your wrist, gravity will pull it downward in different directions, depending on the orientation of the watch, if you are playing a sport, or simply knock the watch on the wall or desk by mistake, you are subjecting the watch to a lot of movement and potential shocks. So some variation should be acceptable.

How well wound the mainspring is can also have an impact in my experience, a mainspring with less force may make a watch run slower. (I have an watch running a Selitta SW-220 movement that does this).

That's just my two centimes of thought though...

Thanks so much for all of the replies.


Yes, sorry... I got it new in 2010. Wedding gift. I have been the only owner, the watch has had a peaceful life so far.. looks brand new. Just never have had it serviced. I have conflicting thoughts on it.. but, now I can see it needs to be done. So, I plan on ponying up the money and sending it to Omega in the fall when this covid mess calms down. Right now, when I called they said its about 4 month turnaround.. so, I am going to wait so I can get it back a bit sooner and not be so long without my watch. EDIT. my watch has the 2500C movement in it.

Hey SunTiger, sounds like you are tracking the watches just like me😀
'time.is' is my reference point, first I manually wind the watch up (fully) then wear the watch whole week and check the gain/loss 3 times per day, I do my best to do the check at the same/very similar hours, every 8 hours let's say.
For the night I put the watch crown up, or crown down of face up.
Then I put it into a spreadsheet and calculate delta(1) which is delta between 3 daily checks, and also delta(2) which is focused only on the night results when watch is resting in a various positions.
I think this is the simplest method to do your homemade-COSC-light test (temperature and atmospheric pressure I don't care).


No, it is not a general rule, all depends on the watch/movement how it reacts to a various position, have a look here please;

This is my very consistent aka boring as hell watch which does not care much about the positions;


and here is the watch which does not like resting in "crown down" position.


It is probably each to their own. Some put a watch on a timegrapher, others will use apps to track the accuracy, I am not a fan of those apps as they measure an average between the days/test results, that's kinda funny method me thinks. Some other people will log the accuracy in the own tests.
As you are already on your own log, do consider checking a delta between the various horizontal&vertical positions😉

Have fun!

Can you imagine tracking a watch so closely that if you wore it one day, you'd feel the compulsion to leave it untouched (apart from winding) face up for 4 days to cancel out the gain? Perhaps left for an additional 2 days to partially mitigate the gain from wearing it again on the 8th day and repeating 1 day on, 4 days off? And if you didn't wear it but left it face up for 2 days, then 3 days crown-up before repeating this alternate 5-day cycle?

Actually yes, I think a number of people here can imagine that. 🙄