Bezel calculations & migraine

So you’ve got yourself that great looking watch with an equally great and complicated looking bezel – you know the one with all those tiny text figures on it,  that 9 out or 10 folks have not a clue as to what they mean, let alone use them!  And having quite a few of those models myself, I thought I’d shed some light (or not) on some of the things you can calculate with them and basically because my Skyhawk provides this data in the instructions.

However not all bezel markings are the same.  There is the simple Divers Count Up bezel marked 0 to 60, then the Count Down bezel marked 60 to 0 (useful for that parking meter), or the Speedmaster style Tachymeter scale for measuring units per time increments such as your speed in miles per hour etc, then there is the Pulsometer, used to check your heart rate and maybe incorporated with an Asthmometer to calculate your respiratory rate.  Not so often you also find the Telemeter bezel where you can determine the distance you are from a sound, such as thunder in a storm for example and of course there’s the GMT bezel with its 24 hr graduations and useful as a Dual Time indicator, then there’s the Compass bezel which is not a compass, but makes rough bearings possible – and lastly there’s the Slide Rule bezel, such as the one on my Skyhawk, which typical for Citizen, seems to have every one of ’em!

But before it gets too complicated here’s a “Hint” – I love this, that one of the watch brands gives as a helpful piece of information to the potential watch Slide Rule user –

Nothing to it Really!

This is a hint?  Well thanks for that! (Courtesy of Seiko)

So there, that explains everything doesn’t it?  Or like me you got lost when the n-th bit and the 10 to the little y came along!  But no worries if you’ve got your iPhone with you then forget the watch!  Ha Ha!
And I’m being serious here as unless your eyesight is A+++ then trying to work out anything on these watch bezels is nigh impossible.  I tried it on my Skyhawk and with a magnifying glass, a bright light plus the instructions booklet to hand and accompanied by an inordinate amount of cursing, all I got was a serious migraine!

Citizen Skyhawk - home at last.

Bezel Slide Rule with movable, Outer Rule, fixed Inner rule and in-dial fixed Index – allows many calculations.

Now OK the lesser bezels such as the 0-60 and 60-0, compass, GMT and so on, these are useful and no problem (they’re also bigger textually), but the old Slide Rule is a killer, basically for me because the text is too darned small.  In fact I pulled out my old Slide Rule (yes I do have one from the dark ages when engineer and eyesight were not diametrically opposed) and would you believe it the text was almost the same darned size!

Suffice to say I struggled to even read it – so for me I’m happy to have my pilot/engineer/macho bezel watch, but I’ll use it, thank you very much, to tell the time!

However for those of you with decent eyesight and perhaps owning a pre-owned Slide Rule bezel watch with no instructions – then this next bit is for you – maybe!


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen


© Citizen

That covers some of the calculations possible with the circular Slide Rule, certainly on the Citizen Skyhawk and I suppose (eyesight permitting) if you use some of these calculations (especially the Navigation ones) then in the absence of other electronic aids, it could well be a useful item on your wrist.  However many folks like myself now will but this type of watch for the looks and the aesthetics rather than any technical calculation functionality, though it’s nice to know that there are some calculations that are not too difficult to manage should the need arise.

Other bezel styles such as the Telemeter basically indicates the distance from your location to an object that emits both light and sound, such as when thunder and lightening occurs. basically the difference between the Speed of Light (almost immediately) and the Speed of Sound (0.33km/second).

Courtesy of Seiko Watch Co.

Image © Seiko Watch Co. – Note other models may have a different stopwatch sequence.

I’ve more or less just scratched the surface here on circular Slide Rule and bezel indexes as the calculations possible are many.  Multiplication, Division, Ratios, Volume unit conversion, Weight unit conversion, Distance conversion, Fuel conversion, Distance conversion, Time to Distance, Calculation of Speed, Driving distance, Fuel consumption (rate & amount), Driving times, Wind direction for yachting for example and similar calculations for flying etc.  the list is pretty long.
In fact the E6B flight computer or the “whiz wheel” as sometimes called, is a form of circular slide rule used in aviation, though maybe now mostly used in training, as today electronic Flight Computers have taken over.  But these slide rule computers (for that’s essentially what they are) may be used in flight planning prior to take off for calculating fuel use, wind direction, flight times, ground speed, estimated arrival times and so on and I well remember seeing Pilots with the slide rule sticking up out of their Flight bag walking to the aircraft.

So on the main Brands of pilot watch and other models featuring Slide Rules, the function is not just a gimmick as you might think, because in essence they do work – IF you know how . . .
However for me, what with the eyesight and brain limitation today, I’ll just have to wear my Slide Rule bezel models with all the confidence I can muster.

And as for using the calculation bit, well I don’t really think I have the patience these days nor indeed the Time to learn!

But my Skyhawk is a great watch – so there!

However – I hope some of you out there found the above useful and all I can say is – have fun!

Categories: Commentary


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