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?
Re: Diagonal vs. image erector
#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.
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?
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.