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Equipment Discussions >> Refractors

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evilmedic13
member


Reged: 06/23/12

Loc: Chicago,Il
Scope choice for multi use new
      #5646200 - 01/27/13 02:48 PM

I've narrowed my field down to the ES80 apo vs AT72 Ed. I'll be using it as an AP/guide/grab n go scope. I know the 80 is a triplet and 72 is a doublet but, I've also read that its all in he glass by many. I'll be using it atop my nexstar11 and ES127 apo. It will be a cgem dx with the 127 and on a wedge with the n11. Aside from cost, is there really a big difference between the 2 as far as aperture and glass?

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sg6
professor emeritus


Reged: 02/14/10

Loc: Norfolk, UK.
Re: Scope choice for multi use new [Re: evilmedic13]
      #5646536 - 01/27/13 05:49 PM

A doublet allows 2 wavelengths to be at the same focal plane, a triplet allows 3.
So not all in the glass, a triplet with FPL-51 will outperform a doublet with FPL-53.

As a do everything well scope get the 80.


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evilmedic13
member


Reged: 06/23/12

Loc: Chicago,Il
Re: Scope choice for multi use new [Re: sg6]
      #5646698 - 01/27/13 06:55 PM

Thanks sg6. That was my thought as well, just needed a little back g to be sure.

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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Scope choice for multi use [Re: sg6]
      #5647434 - 01/28/13 05:45 AM

Quote:

A doublet allows 2 wavelengths to be at the same focal plane, a triplet allows 3.
So not all in the glass, a triplet with FPL-51 will outperform a doublet with FPL-53.

As a do everything well scope get the 80.




A doublet also allows three different widely spaced colors to be in focus simultaneously. The color correction depends on more than just the number of elements and the ED Glass used, it depends on the focal ratio, the aperture as well as the design specifics.

Without knowing more, it is not really possible to say how a FPL-51 triplet will compare to an FPL-53 doublet.

But in this case, this is a non-issue since the AT-72ED is an FPL-51 doublet...

Jon


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