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dcriner
member


Reged: 06/08/10

Diagonal vs. image erector
      #6003944 - 08/02/13 08:57 PM

I have a 3.5 duplex that I want to use for terrestrial viewing, through the axial port. I want the image to be correct, vertically - not necessarily left and right. What is the difference between the Questar mirror diagonal and the Questar image erector for this purpose?

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Mike E.
Carpal Tunnel


Reged: 01/26/10

Loc: Moonstone Observatory
Re: Diagonal vs. image erector new [Re: dcriner]
      #6004273 - 08/03/13 02:02 AM

The erector inverts the image to the correct orientation for terestrial views.
Questar lists two models of image erectors.....
1.) A straight through # 19450
2.) A premium 45 degree amici prism # 19451.


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Les
scholastic sledgehammer
*****

Reged: 04/22/06

Loc: Maryland
Re: Diagonal vs. image erector new [Re: dcriner]
      #6004532 - 08/03/13 10:13 AM

Just to be clear:

http://www.telescope.com/Articles/Current-Articles/Telescopes/Image-Orientati...

Both present correct orientation vertically. If that is your only requirement then go with the diagonal because it uses less optical surfaces (one) that can degrade image.


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dcriner
member


Reged: 06/08/10

Re: Diagonal vs. image erector new [Re: Les]
      #6005216 - 08/03/13 06:33 PM

Mike & Les - that's very helpful advice, thanks. I'm now leaning toward the 45-deg erecting prism - not because I can't deal with a mirror image, but because the 45 deg will be easier to deal with for terrestrial viewing. For the 90-deg mirror diagonal, I might as well look down into an eyepiece in the usual location on the top of the barrel of the 'scope?

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dcriner
member


Reged: 06/08/10

Re: Diagonal vs. image erector new [Re: dcriner]
      #6033615 - 08/18/13 09:07 PM

I have received the 45-deg erecting prism. It serves my purposes for terrestrial viewing, fine. Of course, since it threads into the axial port, it does not work with the viewfinder or the built-in Barlow. For a viewfinder, use a long-focal-length eyepiece in the top position of the 'scope - which will also work with the built-in viewfinder.

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