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Celestron Erect Image Prism for Refractor and Schmidt Cassegrain


Did you know that most telescopes work well for daytime viewing as well as for
astronomy?  If you have a refractor or a catadioptric telescope (the Schmidt-
Cassegrain is the most popular example), and you would like to use it for
terrestrial observations, the most useful additional accessory you can buy is
an erect-image diagonal. If you look through your telescope with the standard
mirror or star diagonal installed, you will notice that objects may be either
upside down, flipped so that you see a mirror image, or a combination of the
two.  This is fine for observations of celestial objects, but it can be a
little confusing when you are trying to track a boat as it moves through the
water, or an eagle as he flies towards his perch.  Luckily, this is an easy
problem to correct.  Simply remove the standard diagonal from the telescope’s
focuser or visual back, and install the Celestron 45º Erect Image Diagonal.
Now, when you insert an eyepiece, objects will be right side up and left-to-
right correct.  The 45º angle of this Amici prism diagonal is very comfortable
for daytime observations, where the telescope is often in a horizontal
position. Please Note:  Adding an erect-image diagonal to a Newtonian
reflector will not result in images that are right side up and left-to-right
correct.  The optical design of a Newtonian will always produce images that
are rotationally off in orientation.  This does not mean that you can’t use a
Newtonian reflector during the day, it just means that you have to get used to
objects oriented in unrealistic positions.


  • A great accessory for daytime terrestrial viewing with your telescope
  • This 1.25 diagonal produces right side up and left-to-right correct images when used with refractors and catadioptric (Schmidt-Cassegrain) telescopes
  • Inserts into 1.25 focusers or visual backs. Accepts standard 1.25 eyepieces

Product Details:

  • Product Dimensions: 4.4 x 3 x 2.1 inches
  • Item Weight: 4.8 ounces
  • Shipping Weight: 4.8 ounces
  • Item model number: 94112-A
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Filed under: Eyepieces & Accessories