I am hoping that I do not get into too much trouble as the subject of the "best" movement could bring forth strong emotions. ETA vs Citizen vs Seiko vs Omega vs ???.
With the above in mind, I am going to keep to the facts as I have found them.
I have subjected quite a few watch movements to rate evaluations over the temperature range of 78 to 96 deg. F. Some thermally insensitive via crystal design (Seiko 8Fxx and Omega Marine Chronometer) and some via careful crystal selection and active compensation (Citizen A660H, Citizen E510, Seiko 9Fxx, and ETA).
The results are interesting and somewhat unexpected. That could be simply the result of a small data set or what is actually happening. I don't know for sure.
The first figure below shows the change in rate vs temperature using deg. 78 F as the zero point. Data for nine movements is shown:
- Citizen Exceed with E510
- The Citizen with A660H (2 movements)
- Longines VHP with ETA 252.611
- Longines VHP with ETA 255.563
- Longines VHP with ETA 252.561
- Omega Constellation Perpetual ETA unknown
- Omega Marine Chronometer with 1516
- Grand Seiko with 9F62
The Omega Constellation movement is unknown since I have not yet cracked the case to check the ETA number inside.
The second figure shows the set with the "bad actors" removed. Here a bad actor is any movement that deviated more than 10 sec/yr from the rate at 78 deg. F.
Loosing the Omega Constellation was not a surprise as I have found that the ETA movements perform better with respect to thermal compensation the better their base rate is adjusted. This particular watch has not been adjusted. The Longines VHP's all have been more closely adjusted.
The big surprise is loosing both Citizen A660H movements. Both movements drifted from the base rate consistently as the temperature was increased. By contrast, the Citizen E510 movement's rate deviated at first and then stabilized.
All three Longines VHP's did well as did the Omega Marine Chronometer. The OMC's insensitivity is quite amazing considering its age and the state of the art in reducing thermal drift in the 1970's.
The best performing movement was the Grand Seiko 9F62. It's ability to compensate for temperature changes was quite amazing. In fact, I had to use a bright color to get the 9F's line to show up from the zero departure line on the figure.
So let's have some discussion. What happened to the Citizen A660H movements? Bad examples or is the E510 movement superior. Maybe with a little extra love and care at the factory, the Citizen E510 could be the new Asian leader?????
I have also posted PDF files of the same images so the information can be downloaded and viewed.