# Bulova Moon watch accuracy over 1 year measurement: -5 s



## BabyJoe (Jul 20, 2007)

Bulova Moon watch accuracy 262khz










I used the WatchCheck app which uses GPS and NTP to sync with.
3 Aug 2017 to 29 Aug 2018, almost 13 months: lost 5.1 seconds! Perhaps +/- 0.3s measurement error for pressing the sync button.

Conclusion: this particular watch does indeed do <10s yearly!


----------



## simpletreasures (Apr 22, 2012)

I'd say congratulations!:-!

Maybe I should congratulate Bulova....:-s


----------



## odd_and_vintage_fan (Dec 4, 2014)

Mine's been steady at -12spy since April of 2016. No complaints here.


----------



## BenchGuy (Sep 23, 2012)

I would prefer +5 s/year. Then you could hack it to correct the error. Most quartz watches are biased to gain. 

As a watchmaker I usually bias hacking watches to + and non-hacking to - error. 

The 262 is not temperature compensated...and frequency usually slows with deviation from target temperature. Did you wear the watch daily for the entire test period...or intermittently? 

That said...5 s/year in either direction is pretty remarkable...and with many Atomic time-linked clocks you can have up to 1.5 s error at any given time. 

Regards, BG


----------



## BabyJoe (Jul 20, 2007)

I also prefer watches to be slightly fast instead of slow. (BTW, why don't you do all watches fast, why non-hacking set to be slow?)
I didn't wear the watch very regularly. Circa once per week. The rest of the time it was in my room, which ranges from 15 °C most of the year and up to 30°C in summer.


----------



## BenchGuy (Sep 23, 2012)

BabyJoe said:


> I also prefer watches to be slightly fast instead of slow. (BTW, why don't you do all watches fast, why non-hacking set to be slow?)
> I didn't wear the watch very regularly. Circa once per week. The rest of the time it was in my room, which ranges from 15 °C most of the year and up to 30°C in summer.


Non-hacking regulated slow so that you advance the hands clockwise periodically to correct the time. Anticlockwise may put reverse power on the train...and since the movement does not hack, the escapement is not protected if cannon pinion friction is excessive.

As I understand it, 262kHz is set up for operation on the wrist...if you wore it daily, the average temperature would be different...this would affect accuracy.

Regards, 
BG


----------



## jkpa (Feb 8, 2014)

Great movement, full stop. Just bought my second today.


----------



## abraxas (Feb 13, 2006)

"Bulova engineers tackled the problem of temperature fluctuation by adding temperature regulation to the Precisionist's circuitry. The circuitry in the watch essentially senses temperature changes and adapts to corresponding changes in the quartz crystal's electric pulses. It's a small adjustment that might seem too miniscule to bother with, but tiny changes in pulse strength at the crystal's high oscillation frequency can add up to accuracy-killing deviations as the temperature changes [sources: Lombardi; DiFranco]."

https://electronics.howstuffworks.com/gadgets/clocks-watches/bulova-precisionist3.htm


----------



## signum8 (May 3, 2018)

I'm relatively new to Bulova's precisionist line, having gone through many quartz and time signal controlled watches.

When I set and check my watches, either my Oregon Scientific (WWVB) or the Android/Apple free Atomic Time (NTP) app are reliable standards.

My Precisionist models:

Model 96B257 Stainless steel, blue face, black leather band purchased from Amazon June 1st and since setting it that day, is only 1s fast. $129 then, now $199
Model 98B267 Rose Gold/Stainless steel/brown leather band, purchased May 3rd, but reset and staying on track. $189 then, $199 now.
Model 98B294 2017 Grammy Special, black rubber strap, so far keeping on time. Amazon has dropped the price to $199

I'm really impressed I can get that kind of precision for less than $400, considering quartz watches tend to drift 5-15 seconds per month. At 262 kHz, a sweeping hand is a bonus. 

Gene


----------



## BillSWPA (Feb 19, 2015)

BenchGuy said:


> As I understand it, 262kHz is set up for operation on the wrist...if you wore it daily, the average temperature would be different...this would affect accuracy.
> 
> Regards,
> BG


Interesting. I wore my Sea King daily for a year. During that time, it ran slightly slow. While I did not formally track deviation, I can say with a high degree of confidence that it ran less than 10 sec./year slow. Lately it has been in a drawer, and is running a small amount faster than 10 sec./year. At +0.048 sec./day, I am happy.

Sent from my iPhone using Tapatalk


----------



## mlvjo49 (Feb 17, 2007)

I've had my Lunar Pilot watch for seven months and pretty much wear it every day. Amazingly, it may have deviated by a half second here or there but, by and large, it has been on the nose accurate according to the Atomic Time web site. I have never had a watch even close to this in accuracy and couldn't be happier with it.


----------



## BenchGuy (Sep 23, 2012)

abraxas said:


> "Bulova engineers tackled the problem of temperature fluctuation by adding temperature regulation to the Precisionist's circuitry. The circuitry in the watch essentially senses temperature changes and adapts to corresponding changes in the quartz crystal's electric pulses. It's a small adjustment that might seem too miniscule to bother with, but tiny changes in pulse strength at the crystal's high oscillation frequency can add up to accuracy-killing deviations as the temperature changes [sources: Lombardi; DiFranco]."
> ...


I don't think the issue is signal strength...but rather signal *frequency*...

Frequency varies according to: crystal cut, capacitance and temperature. Conventional quartz crystals are designed and selected to operate at slightly above the target frequency...then trimming circuitry is used to correct. Temperature-corrected adds circuitry to fine tune the trimming for temperature.

Regards, BG


----------



## pfogle (May 18, 2008)

Here are my results over three months for my three Bulovas - a Precisionist, a Lobster Accutron II and one of the first edition of the moon watch.

The projected deviations are Precisionist and Moonwatch, +7sec/yr and the Lobster -3.5 sec/yr. The Lobster shows the most variation - I'm not sure if that movement is temperature compensated as the others are.


----------



## pfogle (May 18, 2008)

Here are my results over three months for my three Bulovas - a Precisionist, a Lobster Accutron II and one of the first edition of the moon watch.

The projected deviations are Precisionist and Moonwatch, +7sec/yr and the Lobster -3.5 sec/yr. The Lobster shows the most variation - I'm not sure if that movement is temperature compensated as the others are.

View attachment 13574429


----------



## pfogle (May 18, 2008)

Hmm, any way to delete unwanted posts?


----------

