Use of Metric & Imperial units of measurement.

[Alfian]

Has anyone any idea on how the dual system of  metric/imperial has come into use on astronomical equipment. I've recently been looking at a 102 refractor, indeed until very recently I had 102Mak. That I assume comes from 4" being 101.6 mm. I also seem to remember once seeing a 6" reflector specified as 153,although it should be nearer 152. Mostly now its  shown as just 150. The Evostar Pro 100ED I assume is 100 and not 102. I suppose the most common odd mixture is the use of 1.25" and 2" focusers and diagonals on scopes where everything else is metric.  Has this just evolved from makers of equipment from different countries, that use different systems of measurement,  just being accommodating.  Given the international nature of astronomical study and research and the global economy I would have thought that sometime way back sometime in the last century some kind of international scientific equipment manufacturing conference would have met and agreed a common system.  Perhaps I am being ignorant or naive or both, but it does seem somewhat idiosyncratic in the 21st Century.

[Charic]

Probably just not updated to  the metric system, whether thats just laziness if folk find it easier to use the imperial system.
Same with   flying, we still use flight levels in Feet, in our cars we like MPH instead of KMs.
And many items are rounded as you suggest, My 200P is  really 203.1mm its now an f/5.91. OhNo!  I`ll have to get some better EPs?

[SilverAstro]

Habit and continuity ?

If everyone already has a 2" hole then continue making 2" eypieces to go in it, and old codgers already know the sorts of things that a 6" can see ! If you keep the real dimension constant you end up with silly decimals when the literature is converted to mm The thing that realy amuses me are the adverts that say ' xx% more light than a nn" ' which is no good at all if I have not got a nn"

Anyway, it isnt really international scientific equipment, more like cheap stuff for amateurs

 

[Gina]

We and the rest of Europe use the metric system whereas the Americans and some others use the imperial system as we used to years ago (and I still do a lot of the time).

[Ouroboros]

I always assumed it was because America remained the dominant manufacturer until quite recently. A lot of the technical equipment we bought and used at work was American and used a mixture of English measurements, as they call them, and metric. We had to keep a set of metric and imperial nuts and bolts and allen keys to service them.  

[Peter Drew]

My last proper job before going self employed as a telescope maker was the company jig borer, the top machine shop position. I had an amazing piece of temperature controlled equipment with optical measuring system for zero tolerance work. When we changed to metric the company looked into the cost of converting the machine. They gave me a book of conversion tables!  

[iapa]

47 minutes ago, Charic said:

Probably just not updated to  the metric system, whether thats just laziness if folk find it easier to use the imperial system.
Same with   flying, we still use flight levels in Feet, in our cars we like MPH instead of KMs.
And many items are rounded as you suggest, My 200P is  really 203.1mm its now an f/5.91. OhNo!  I`ll have to get some better EPs?

and traffic reports tell you that traffic speeds are 20mph for 50Km of the M74.

[iapa]

44 minutes ago, Gina said:

We and the rest of Europe use the metric system whereas the Americans and some others use the imperial system as we used to years ago (and I still do a lot of the time).

Hmmm,  milk bottles are still 1pt, as are beer glasses.

Lose packed items still often show imperial prices as well - UK Government gave up trying to make us stop showing imperial weights a few years ago.

Road distances are in miles as is speed - except per my previous where road reports mix and match inconsistently.

There was good deal of conversion and rounding e.g. all tracks were just a conversion the difference fell within tolerances. I remember we did have to start saying 240V instead of 250V - although we didn't change our generators, just the tolerances when specifying it so we could quote 240V but keep generating 250V 

and my SCT has a 2032mm focal length and 8" aperture, but my f5, 400mm FL refractor has an 800m aperture

What it is to live in the UK

[Ouroboros]

I positively prefer imperial units for certain things like road distances, and  indeed with pints of beer! .  In part I think these measurements as much cultural as functional and we should keep them for that reason alone.  

Metric is definitely preferable for "serious stuff" though like manufactured goods, science etc and that's how it should be.  I must have been on the cusp of the metric system arriving in science teaching because in school physics we were still using units like foot pounds, horse power.  But by the time I started O and A level it was all System International - joules, watts etc. 

[Charic]

.......slightly off topic, but was also just reminded of another issue, food labeling? Peanuts - May contain nuts!, Sleeping Pills - May cause drowsiness?
Like I said, off topic, but there will be countless issues where there is a mixing of decimal/imperial numbering  like its a new thing.
Its a visual thing too for me, I see and realize in feet and inches, I calculate distances in hours mins ( especially up  here in Scotland ) I've no idea without looking it up  right now or looking at a road sign how far Aberdeen is away in miles, but I can be at the airport in 1 hour 45 minutes  or  Carlisle in 5 Hours! 

[iapa]

5 minutes ago, Ouroboros said:

I positively prefer imperial units for certain things like road distances, and  indeed with pints of beer! .  In part I think these measurements as much cultural as functional and we should keep them for that reason alone.  

Metric is definitely preferable for "serious stuff" though like manufactured goods, science etc and that's how it should be.  I must have been on the cusp of the metric system arriving in science teaching because in school physics we were still using units like foot pounds, horse power.  But by the time I started O and A level it was all System International - joules, watts etc. 

I was in 1st or 2nd year at school when they introduced funny money. Some text books for maths were using imperial like foot pounds, others were metric.

The engineering and science labs were all metric tho'.

Costs I suppose as in basic maths he units themselves are irrelevant to some extent - it was the calculation, where in th science labels or engineering workshops it was the measurement 1st.

and a dram will never be properly served in multiples of 25ml.

[RayD]

It's ironic that the American system is a derivative adopted from us after the American Revolution, and now they're only one of 3 countries worldwide that still use it (Burma and Liberia being the others I think).

Personally I feel extremely fortunate that I am of an age that I am equally happy using either, and often do, but can see how younger people get confused with the imperial system when adding fractions.  The metric system for me is far easier, but yes it would be nice if it was totally standardised for everything, including road marking etc.

I remember when the weather was always in Fahrenheit, the went to Fahrenheit and Celsius, and of course is now just Celsius.  I always used to convert Celsius back to Fahrenheit, but now do it the other way round.  Like everythingI guess, use it regularly enough and you soon get used to it.

Above noted, whenever I buy a new tape measure, I still hunt to get one with metric and imperial markings, but this is getting harder.

[John]

I think things could be bought in line with the metric system across the board:

"The whole nine yards" could become "The whole 8.2296 meters"

"Give her 25.4mm and she takes 1.6093 km"

Ray Bradbury's classic "Celsius 232.778"

Feel free to add your own

 

 

[ecuador]

I grew up with the metric system and lived for a few years in the US and now in the UK. One of my favorite past-times while in the US was asking well-educated people (mostly phds), seemingly innocuous questions like "say, how many fl oz are there in a quart/gallon" etc. Even though they dealt with fl oz/quart/gallon every day, most would fail miserably in this, with the most common answers being 16 or 64 fl oz in a quart (it's 32), 64 fl oz in a gallon (it's 128). They would at least get the 16 oz in a pint, but, again, these were mostly phds in the sciences...  I would also often get blank stares if I asked about how many inches/feet/yards in a mile. Why continue with a system that is so difficult to use?  And not to mention imprecise at times - e.g. two people with the same height in inches can be visibly different in height...

But I didn't have a problem adapting myself, e.g. lbs, gallons, quarts are easy if you think of them as a bit less than 1/2 kg, 4lt, 1lt respectively, and in time you could use them naturally (unless you needed to convert from fl oz to quarts of course), but the one thing I could not get were Fahrenheit. I looked up the definition to try to make some sense of it (like 0C = ice, 100C = boiling), and found out that 0F is the temperature of a solution of brine (??!!!???) and 96F was the estimate of the temperature of human blood... by using horses!!! That did not help figuring it out!

Then I came to the UK, to discover, in horror, that while the country is part metric, not only is the imperial system, hmm, I'd say "rampant", it is also different than even the US system, because the US was not "really" imperial! So another set of ounces, pints, gallons and this time not on a 16-base system, but a 20-base! Then people started giving me weights in "stones". What do you mean "10 stone", are we talking about small stones/pebbles here, or is it like some huge rocks? Then, I drive on the road and it says "Service area 10m", which is the international way of saying the service area was at 10 meters from that sign, so long gone by now. At least the americans would write "10 miles", or "10 mi".

I hope I don't offend too many people, but your units suck!

[Filroden]

I'd just assumed the imperial measures were now just marketing approximations and that everything was manufactured in metric (so it was suitable for all markets). Given the largest markets are all metric this would make sense. Are they really 1 1/4" eyepieces and filters or are they 31mm and just sold as 1 1/4"? I have a 9.25" aperture scope but it really is a 235mm aperture.

Regardless, it's so much easier to do all calculations in metric even if it means converting from and then back into imperial for reporting (take note NASA ).

[Filroden]

3 minutes ago, ecuador said:

 And not to mention imprecise at times - e.g. two people with the same height in inches can be visibly different in height...

Surely that's nothing to do with the units of measure but of the person doing the measurement!

[SilverAstro]

33 minutes ago, John said:

I think things could be bought in line with the metric system across the board:

"The whole nine yards" could become "The whole 8.2296 meters"

"Give her 25.4mm and she takes 1.6093 km"

Ray Bradbury's classic "Celsius 232.778"

Feel free to add your own

 

 

I like it !

Anything, anything, whatever you like, but dont you mess with   my blue suade shoes   Ray Bradbury  

[ecuador]

6 minutes ago, Filroden said:

Surely that's nothing to do with the units of measure but of the person doing the measurement!

No, for example a person who is is 179.1cm and a person 181.5 cm will both be listed as 5 ft 11, and yet they are visibly different in height. In the metric they will show up as 2 or 3 cm different (1.79 vs 1.81 or 1.82). Sure, you feel strange when people criticize a system you are used to, but, trust me, it sucks!

[RayD]

 

Says it all 

[ecuador]

1 minute ago, RayD said:

 

Says it all 

It's not exactly right though, the US doesn't use stone, that's the UK

[Davey-T]

Kids today don't know etc etc, no fractions  just move the decimal point around to multiply things a child could do it 

Dave

[Mr Spock]

I had this metric/imperial conversation recently.

Pick a random number between 1 and 1000, with at least three decimal places. E.g., 235.428. Now...

Q1) How many grams are in 235.428 tonnes... easy 235,428,000.00 - did it without thinking.

Q2) How many ounces are in 235.428 tons... er... let me get a calculator and give me five minutes...

I know which I'd rather use

[bejay1957]

During my time in grammar school we used metric/celsius/decimal, and when I moved into industry it was the same metric/celsius - imperial units are meaningless to me.

[SilverAstro]

My problem is that I instinctively know how far 1ml to the nearest pub is but not a clue if told it in km. But I admit that I nolonger think in thou and have adopted mm for tiddly wee  things.

Also, I was quite happy with metric and SI and celsius etc.  things  in the lab, but at home I need it in F to know if it is summer Wx out in the garden by the pool !!!

[Alien 13]

The metric system doesn't work to well if you are cutting a cake or sharing out blackjacks etc.

Alan