I have recently bought omega speedmaster co-axial moonwatch. I'm realizing now that after every 2-3 days watch time goes ahead to 15sec than normal time. I have also reset so many time but problem is continue.. plz suggest thanks
Your watch is accurate to 0 to +5 seconds a day in average of all positions from the factory. Try leaving your watch in a different orientation to gravity at night. Watches keep slightly different time in different positions.
Are you checking this every day? Just check the time after 3-4 weeks and see what the average per day is. It will run slower or faster depending on your normal daily activity. Maybe it is fine. You should not have to change your lifestyle on account of your watch.
So that is about 4min per month + or -. To me that is not good for a COSC certified watch, but it may be perfectly acceptable to someone else. You could have it adjusted. But keep in mind that mechanical watches will not approach the accuracy of even a cheap quartz watch. So you should keep this in perspective. Here is an interesting item I found on accuracy. I'm sure there are other sites out there with similar information. https://www.prestigetime.com/page.php?accuracy
Crown up, crown down, face up, face down. I tracked my watch overnight to see which position worked best
The reason is the hair spring that actually keeps time is affected by gravity. It's actually a technological problem in time keeping. This is why we had pocket watches for so long they where designed to keep great time in one orientation. They had to solve that before wrist watches could be used on trains, which required great accuracy.
And don't forget the internal air pressure. The denser the air, the harder it is for the balance wheel to spin. As the watch cools, the air becomes less dense so providing less boundary layer friction to the spinning mass and the watch will gain time. The best solution is to keep the watch at a constant temperature, ideally 98.6°F (37°C).
Gravity mostly affects the balance, not the hairspring which is more affected (much less since the elinvar and other new materials) by temperature. The variations over 6 positions mainly depend on the poising (static and dynamic) of the balance. Concerning the OP's watch, I guess + 5 sec a day is not an issue, in particular if it is a constant rate. Is it in Omega's specs for such a watch - with the coaxial escapement? Al may tell us.