sorta OT 40 year ago

Classic moments in history. A time where everything seemed possible.

Merry Christmas to all that observe it and have a great day for the others.

Wes

It is truly impressive this all happened when people used slide rules and punch cards.

Now NASA can't even QC a telescope before putting it into orbit.

Her is more

-- Boris

Now there's an interesting story, wish I could remember the book detailing the history of the Hubble's optical problem - the problem was partially that the budget bean counters wouldn't allow an "end-to- end-test" before launch, something the builders of the optics, Perkin- Elmer had never encountered in all the satellite optics they had built for the military. The second problem was a poorly designed spacer and mirror mount that was used for an in house mirror test to check that the mirror was ground correctly (as I recall it was called a "null test", but don't hold me to it). The spacer and mount could be assembled in 2 different ways, and it was assembled wrong, resulting in a perfectly ground mirror that was ground to the wrong "prescription". The error was so "gross" that P-E couldn't believe that there was that much spherical aberration in the Hubble's main mirror - they never made mistakes of that order of magnitude. The book is well worth reading if you think the govt driven aerospace industry can't do anything wrong... Joel in Florida - I used to teach optics in a previous existence.

The best part of all is Kodak made the "backup" mirror, which was perfect and never used.

whoops.

Itek (now PE) did propose to NASA a full up system test, for $2mil, but the option was not purchased.

Almost. There were two null correctors built, one very fancy and accurate, with custom-ground optics, the other being simpler and made from catalog optical elements. The two null correctors gave different answers. NASA chose to believe the fancy null corrector, which claimed that the mirror was perfect.

Turned out to be a bad move. If there had been any real optical experts in charge, a third null corrector would have been fabricated by an independent group of people, and then it would have been clear that the fancy null corrector was built wrong.

The problem with the fancy null corrector was that a spacer was made wrong, being a millimeter too short or too long. Don't recall why.

My information comes from a prior boss who worked for Itek at the time.

If you want more, pose the question on "sci.optics". With any luck, there will be some first-person accounts posted.

Joe Gwinn

even better. Nasa was too stupid to even negotiate a sensible contract. You'd thnik they'd have been good at the paper pushing side. Apparently not.

Who buys expensive custom stuff without any testing involved?

WTF

I just missed using tables of logarithms. I don't think I missed much.

A computer once as a girl (typically) with a mechanical calculator in a pool. Things have changed a lot.

Wes

Practically, you missed nothing. In terms of understanding what's going on, you missed a lot. I'm convinced that learning to do calculations with mechanical aids helps a lot with intuitions that you just don't get from a calculator.

One thing I learned from using a slide rule was to be aware of decimal places. You had to have a good idea of the magnitude of the expected answer. It's too easy to slip a decimal place with a calculator.

David

Well, there is that old story about Noah and the snakes.

They couldn't "go forth and multiply" - because they were Adders...

But Noah took them in the kitchen and tossed them on the table where they becan to multiply like crazy!

Because Adders can multiply on a Log Table.

(ducking UNDER the log table now) :))

I still have my 8" Decilon from High Schol.

It didn't even have ANY decimal places.

:) Ducking Again!

I don't think it's just mechanical aids; it's devices that display relationships of proportion -- analog devices, more or less. There is a claustrophobia inherent in many digital devices, including calculators. You got your number, but you still don't know where you are.

When I got my first programmable calculator the first thing I did with it was to produce incremental tables of equations that gave me trouble, so I could easily plot them on graph paper and see the curves, thereby defeating the central purpose of the devices. d8-)

-- Ed Huntress

Between my abacus and my Vista box is where I park my Concise #28 circular slide rule. Gerry :-)} London, Canada

I'll see your Decilon and raise you one "MB-4", from 1959, which states flatly on its face that it is a "COMPUTER, Air Navigation, Dead Reckoning, Specification Mil-C 5414B" And it just happened to be on top of my monitor, right now.

And you are right, it helps to have some idea of where the decimal should be, before you go looking for the result.

Flash

The decimal points were optional equipment, and always out of stock.

Richard wrote in news:OP- dncwRz9TTL8zUnZ2dnUVZ snipped-for-privacy@earthlink.com:

I still use mine plus the 4" Post, a 6" Pickett, and my old Flight Computer with its 4" circular.

The others are in my desk drawer along with my old TI Programmer calculator.

Calculators may give nice, precise decimal responses but for ratios/proportions nothing beats a slipstick.