Telescope sizes: inches vs. mm

I have always found it interesting that we have a weird mix of units when it comes to our scopes. All eyepieces are in millimeters. Newtonians and Schmidt-Cass telescopes, as well as some large refractors are in inches. Binoculars and small refractors are in millimeters. Why don't we change everything to mm and scrap inches. This way we will have our aperture sizes, focal lengths, and eyepieces on the same unit, which would allow for easier calculation of magnifications(no english/metric conversions).
Besides, I would like to call my 16 incher a 400 mm or .4 meter.
Thoughts, anybody?

already do it here in Canada ... eh!

howard

Robert…

I sometimes refer to my 5" SCT as a 1/8 m scope. It sounds so much bigger that way.

BTW, even though I have used the english system all my life, I sure wish we could get over the metric conversion hump here in the USA. As a civil engineer, metric is so much easier, but only my projects for the federal govt require metric. Everything else is in english units.

Fred

"This way we will have our aperture sizes, focal lengths, and eyepieces on the same unit, which would allow for easier calculation of magnifications(no english/metric conversions)."

Speaking purely WRT telescopes, the FL of my 13" is 58.7 inches or 1491mm. Dividing a 13mm EP (for example) into either has to be done with a calculator, so I don't see an advantage. Unless you can do that kind of division in your head! 8O

I've set up a spreadsheet for calculating magnifications for all my eyepiece/telescope combinations so I just let the computer do it for me anyway.

But in general, I agree that the metric system would be easier overall. Powers of 10 are obviously more natural since we all use a base 10 number system (computer geeks like myself notwithstanding).

Best regards,
Doug

As Nigel from Spinal Tap would say:

"But inches are bigger!"
8)
Jarad

The mix isn't likely to go away, as there are two many standards. For eyepieces we have 24.5mm, 1.25 inches, and 2 inches as standard barrel diameters. But in the US, the first size is refered to as 0.9651 inches! Lets drop that one, shall we? The others will just have to stay in inches, because, well, they ARE in inches.

Similarily, my 12.5 inch telescope is (embarrasingly) a 12.5 inch telescope and not a 3175mm one, since its based on a 12.5 inch mirror blank.

Thread measurements for screws, filters, visual backs, and other attachments is another nightmare mix.

Basically, if North America had joined the 19th century in the 19th century, and didn't wait until the late 20th century(Canada), or apparently chose to wait until the late 21st century (USA), then we wouldn't be in this mess. But we are.

After that long chat, everyone deserves a good drink! How about a gallon of water? BUT an "American gallon" (3.785 liters), or a "British gallon" (4.543 liters)???
However, for a Frenchman living in the US, I find the hardest to be the Farenheit system. Frankly, the Celsius scale makes a lot of sense: pure water freezes at sea level at 0°C and boils at 100°C: how about that???

Here's something that always bugged me until I found out the reason. The conversion from inches to centimeters is 2.54. Not 2.54012623478 or 2.540003776234 or some other similar number. Why exactly 2.54? :S

The reason is that the inch is "officially" defined to be 2.54 centimeters. Not sure where I read it but I sleep better now.

Doug

I had a wonderful Triumph Trident motorcycle. English measure throughout, except the carbeurators, which were metric. Except certain other parts, (I forget which) which were Whitworth. Three sets of wrenches mandatory. Not great in that respect.

HOWEVER, I remain a fan of English measure for building things. A lot of building is done by dividing stuff in half. Half of 6-7/8 is 3-7/16, instantly. Probably have to calculate it in metric.

Also, tolerance of plus or minus 1/16th is pretty manageable. Plus or minus 1 mm is too fussy, and 2 mm is often too sloppy.

Steve