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Stranger than fiction!

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#126 Sgt

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Posted 20 January 2012 - 07:43 AM

Neil, my condolences regarding the passing of your father.

#127 astroneil

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Posted 20 January 2012 - 12:30 PM

Sgt,

Thank you. He had a good innings.

Nothing good lasts forever.

Best Wishes,

Neil. ;)

#128 ukcanuck

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Posted 20 January 2012 - 12:41 PM

Neil, I have nothing but admiration for the immense amount of time and work you have put into researching the achromat refractor. :rainbow: While I can build a rather nice one, I would never have been able to put into words (and with scientific justification) why they captivate people the way they do.

Thank you for taking the time, and I wish you much better times ahead for 2012.

#129 astroneil

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Posted 20 January 2012 - 03:17 PM

That's quite intriguing.

I'm looking forward to the whole enchilada.

My longer focal length refractors certainly appear to settle down more quickly and maintain steadier images during the session than do my faster refractors. It's nice to read some ideas as to why that is the case.

Regards,

Jim


Hello Jim,

Yes, it was a rather impulsive posting, that's for sure.

Rest assured though, I will weave that work into my up-and-coming book, a chapter of which will be entitled, "What the Classical Achromat has done for us".

With best wishes,

Neil. ;)

#130 astroneil

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Posted 20 January 2012 - 03:25 PM

Neil, I have nothing but admiration for the immense amount of time and work you have put into researching the achromat refractor. :rainbow: While I can build a rather nice one, I would never have been able to put into words (and with scientific justification) why they captivate people the way they do.

Thank you for taking the time, and I wish you much better times ahead for 2012.


Richard,

It was a pleasure, really. Had you not possessed the vision you had, none of this would ever have happened and we'd be none the wiser.

The War is over.

I'm free now to recount the illustrious history of the classical achromat in all its glory.

Kind regards,

Neil. ;)

#131 astroneil

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Posted 23 January 2012 - 09:14 PM

Hello Jim,

Yes, it was a rather impulsive posting, that's for sure.

Rest assured though, I will weave that work into my up-and-coming book, a chapter of which will be entitled, "What the Classical Achromat has done for us".

With best wishes,

Neil. ;) [/quote]

Actually, I will re-entitle that Chapter. It shall henceforth be called "The Magic Flute," precisely as it had been at its inception, some months back. :)

#132 philjay

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Posted 31 January 2012 - 04:09 PM

Ah found you Neil.
Yet again another fascinating insight into the long focus refractors behaviour.
To we few dedicated band of individuals fighting for the long focus achromat in the APO age what you say just strikes that chord - this is stuff I have noticed subconciously over all the nights I have been using these scopes, now its all been explained its obvious.
So thats why the image is so stable, so thats why it takes less time to get a decent image than my 5" poodle ;)

Thanks for lifting the veil and giving us insight into why these scopes do the things they are so good at, oh and thanks for providing some factual ammo ;)

Good luck and best wishes with the new book, looking forward to it already

Phil

#133 Glassthrower

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Posted 31 January 2012 - 06:21 PM

I've always been a fan of long-focus achromats. Other factors aside, they just look COOLER than a short tube. :)

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#134 astroneil

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Posted 31 January 2012 - 09:31 PM

Elementary my dear Phil. :lol: It just took lots of clever people and over two years of detective work to flesh out all the details. Most of all, it is confirmed by hallowed and sober experience and, to that end, I have a lot of people to thank for taking that leap of faith.

Mike, too right! They are monuments to human genius, as fundamental to our civilization as good literature is.

Alas, the sad reality is that all too often they sit in great, domed Cathedrals that are slowly crumbling away because of lack of interest and/or funding.

Many others have been dismantled for parts and will probably never see the light of night again. :bawling:

Regards,

Neil. ;)

#135 sixela

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Posted 08 February 2012 - 09:38 AM

In fact, there's a very well-known article on a vendor site claiming precisely the contrary; that focal length/ratio has no bearing on image stability.

http://www.fpi-proto...reer/seeing.htm

"Conclusion

Telescopes of equal aperture are affected the same by atmospheric turbulence, regardless of focal ratio. "

Given that this article contradicts that one


They don't contradict each other. They make different assumptions about how well a user can focus a scope in average seeing.

Bryan Greer's article also holds for all types of scopes --given what his company sells and with what instruments he observes, I don't think peculiarities of refractor designs were first and foremost on his mind-- whereas Neil's article is specifically about short APO vs. long achromat refractors (the particular effects that make a little defocus better for the long achromat do not apply to reflectors, who don't have different focus for different colour and spherochromaticism).

In other words: if someone thinks the articles contradict each other, it's useful to reread to understand exactly why the articles seem to contradict each other, to know exactly how the conclusions are qualified (and to understand why there's no paradox).

Neil's article is indeed in itself a very good illustration of why simplified 'conclusions' can be wrong if extrapolated to scenarios where they no longer hold.


#136 jrbarnett

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Posted 08 February 2012 - 11:56 AM

You're correct Alexis. I subsequently discussed this point with Neil. I just never bothered to correct a misstatement I made in October, 2010.

Thanks correcting that. I shudder to think what might have happened had your vigilance slipped. :lol:

- Jim

#137 sixela

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Posted 08 February 2012 - 06:57 PM

Sorry about that -- I didn't bother to read the dates on the contributions. Ah well, at least it's on the record now.






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