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Spurious Accuracy

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Mick B106/11/2017 12:01:32
2444 forum posts
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Posted by Neil Wyatt on 06/11/2017 10:59:27:
The aim is NOT to hit a specific focal length, but to get a near-perfect parabola close to your intended focal length.

Neil

That's why you have an adjustable focusser. And the closer you get to a uniform focal length, the more of your field of view will share a common focus (?).

John Haine06/11/2017 15:47:48
5563 forum posts
322 photos

Thanks for the explanation. Precision then?

Neil Wyatt06/11/2017 18:09:08
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Posted by Mick B1 on 06/11/2017 12:01:32:
Posted by Neil Wyatt on 06/11/2017 10:59:27:
The aim is NOT to hit a specific focal length, but to get a near-perfect parabola close to your intended focal length.

Neil

That's why you have an adjustable focusser. And the closer you get to a uniform focal length, the more of your field of view will share a common focus (?).

And because people have different eyes, cameras and eyepieces!

To get a sharp image across the field, reflectors of about F5 and faster need a 'coma corrector' as stars near the edge get 'stretched'

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