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Being ancient, techno-phopic, anti-decimal (still do revenue calculations in groats), can anyone tell me why refractors, Newtonians and compounds are frequently referred to in Metric terms yet Dobsonians invariably in Imperial mensuration?

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Yep I'm with you on this - to this day I just can't visualise scope diameters in mm. It's a pita having to translate everything into Imperial just to understand what's being said/written.

I guess it's all down to what you learned in school, but give me inches any day and I'll "see" it in my minds eye instantly. However - working out the magnification of a 10mm eyepiece in a 1500mm focal length dob is so convenient :BangHead:

Edited by brantuk
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why refractors, Newtonians and compounds are frequently referred to in Metric terms yet Dobsonians invariably in Imperial mensuration?

Well, the whole world :BangHead: works in metric - plus it makes the numbers sound bigger.

I'm not sure that dob sizes are quoted in inches as a rule - although SCTs do tend to be. I'd reckon that because they're mostly american products and they bring their "old fashioned" units with them?

Edited by pete_l
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Well, the whole world :BangHead: works in metric - plus it makes the numbers sound bigger.

I'm not sure that dob sizes are quoted in inches as a rule - although SCTs do tend to be. I'd reckon that because they're mostly american products and they bring their "old fashioned" units with them?

Not entirely true, I wasn't doing 112.6 KM per hour on the way to work this morning ............ I was doing 70 miles per hour ;)

Edited by Stephen
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Interesting. My SCT is definitely 9.25 inches and I have to struggle to remember that is 2350mm when wanting to calculate the magnification. (Usually for the sake of a member of the public at an open evening - I just think about what eyepiece I'm going to use)

However my refractor is firstly 102mm (rather than 4 inches) probably as the model number is FL102S.

Dave

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For old gits like me brought up on the good old imperial system I have got used to using the mix of both - electrical engineering in the 50s/60s obliged familiarity with the MKS system (metre, kilogram, second) and greek alphabet symbol notation - as we see commonly in astronomy - lambda, theta etc. Weather is totally metric whereas road speed is in imperial. So 8", 80mm, 1200mm, whatever. I use and think in terms of what suits me at the time - timbering at home uses a mix of both.

But I miss, 240:1, 16:1, 5280:1 and all the other straightforward 20 cwts in a ton.

Guess its progress??????

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Dear Dave - i hope your SCT is 235mm dia - otherwise it is kin huge:eek::BangHead::eek:

sorry - just another metro-imperial pedant:rolleyes:

"Dave Smith; Interesting. My SCT is definitely 9.25 inches and I have to struggle to remember that is 2350mm when wanting to calculate the magnification."

Edited by Photohound
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Dear Dave - i hope your SCT is 235mm dia - otherwise it is kin huge:eek::BangHead::eek:

sorry - just another metro-imperial pedant:rolleyes:

"Dave Smith; Interesting. My SCT is definitely 9.25 inches and I have to struggle to remember that is 2350mm when wanting to calculate the magnification."

Yep - You see my problem! 2350mm is of course the focal length, but I was correct in that I need the focal length to calculate the magnification.

Dave

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Glad that the lighter side of the astro mob still exists, on this side of the pond anyway.

oldgit, are you the old git on the saxophone forums? Well remember the MKS system when in the combined Imp/Metric system but only millimetres and metres were allowed on our radar blueprints. Some dimensions took longer to say than measure. It is also necessary to ask Nova how many millilitres there are in an American pint for our Cousins education as their system is pre Imperial.

Thanks for all the laughs.

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Not sure if it is true, but i think i read somewhere that the USA is metric legally, but they just wont use it.

I use cad programs for a living and hate imperial, metric is much better!!!

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Not sure if it is true, but i think i read somewhere that the USA is metric legally, but they just wont use it.

Federal laws have been passed, but individual state laws tend to get in the way of conversion for a lot of processes and items. In most cases, conversion has occurred relating to trade goods.

Here in the US it has been a long road to officially converting to metrics, and I am not sure it will happen completely (or much more than it has) in my lifetime. I remember being told in school during the 60’s it was coming and we had to learn the “new” system because things were changing……. Still waiting. It’s a mixed bag here many areas , 12 oz. cans and 2 liter bottles of the same product?!?

Imperial (United States customary system) values will remain in use in the states for quite awhile. Race fans won’t stand for a Daytona or Indy 804 (unless it’s 804 miles)!;)

Hell, we still use the old Penny system (8d, 10d, etc.) for nails sizes. I mean that isn’t even used in the UK any more, is it? Go figure.:BangHead:

"We're going metric inch by inch :)"

DoctorD, that is a bumber sticker waiting to be made!!!

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I was of the generation that learned both at school and is therefore among the last to have any inkling of what Imperial units mean. My children work only in metric and have no idea what an inch is, or how many pounds are in a stone. Their only lapse is that they work in miles rather than kilometres.

Money switched over when I was a mere 4 or 5. My dad owned a shop then (a proper Open All Hours shop with him as Arkwright) and so the changeover is etched in my mind, along with the little rhymes we were given to remember the conversions ("Sixpence is two-and-a-half-new pence"). The money really did need changing though. Who on earth thought of a system that was as cubersome as pounds, shillings and pence!

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What!!!!!! I am not a "metricphobic" but the passing of LSD was a very sad day. I still understand and remember the imperial currency as if it were today. I think also that it was a boon to numeracy skills as were all imperial measures.

The lowest denomination was the farthing of which there were 4 to a 1d and 960/£. You could buy an oxo for a 1/4d. And the dear old ha'penny complete with the maritime ha'penny galleon on the obverse. Decimal was immediately inflationary and the 1/2p was rapidly disposed of. I can appreciate decimal is simple but so was LSD to all - had to be in those days of austerity. My first wage was £2.12.6d = £2.625. ??

I put it down to the Common Market or is it EU now. Nostalgic? Maybe.

(Beginning to sound like my mother)

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"The money really did need changing though. Who on earth thought of a system that was as cubersome as pounds, shillings and pence!"

I rather think it didn't actually need changing. If you dig deep enough I think you'll find that a lot of rich and greedy people saw a very easy way of doubling their fortunes whilst conning everyone into thinking it was to simplify things for the public and fall in line with Europe (still a separate country if you ask me lol).

I remember only too well, as a kid, how the price of sweets more than doubled as a result of decimalisation. Sweets costing 1d went up overnight to 1p (the eqivalent of 2.4 old pennies).

I can well recall how baffled I was when we just sat back and did nothing about the massive rip off - my very first financial lesson lol :BangHead:

(My first wage was £21 per week - wouldn't even buy a decent eyepiece nowadays lol)

Edited by brantuk
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