Re: [ATM] Another Astigmatism question, but at the sphere stage

["john sherman" <atm@mail.johnspics.com>]

Hey Vlad!

>John Sherman wrote:
>
>>And "stigmatic" meant that your scope produced a round, 
>>pinpoint image of a star 

>Like you said, there is specific meaning agreed upon as to what
>"astigmatism" and "astigmatic" mean in optics, and it relates to
>both particular surface deformations, and their effect on the
>point image. It wouldn't help clarity if we start using these words
>for other surface deformations and their effects, just because it >wouldn't be in disagreement with the original general meaning. 
>
>But it does make for an interesting chat...


A long time ago I was a child raised in Hawaii. My dad would take me down to see the fishing boats (yes, this was a LONG time ago). The fishermen used to hate the ignorant folks who called a porpoise a dolphin. [a porpoise is a mammal, a dolphin is a green and yellow fish] Seems that some time ago a sailor saw a porpoise and since it had a forehead, he called it a dolphin. 

Big mistake!! 

Yet that error caught on! And now when you Google dolphin you find pictures of porpoises. Only the better sources also mention dolphins the fish. I can imagine how horrified those old fishermen and sailors would be today. We have completely perverted the meaning of the word. 


So I can also imagine that the opticians of old would be equally horrified at our modern definition of astigmatism. Because, we have changed the original definition. We now refer only to a certain defect as (primary) astigmatism, and we reject the original meaning.

But it is what it is. And I agree with you and Mike, since we have a meaning which we agree on today, even tho itz perverted, we should stick to it.

Take care,

John







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