GSO 0.965"/1.25" 90-deg Hybrid Erect-Image Prism Diagonal

Our Price: $33.00
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Manufacturer SKU: ODIA-GS-PD90-HYBRID
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GSO 0.965"/1.25" 90-deg Hybrid Erect-Image Prism Diagonal # EIDH90

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  • GSO 0.965"/1.25" 90-deg Hybrid Erect-Image Prism Diagonal # EIDH90
  • GSO 0.965"/1.25" 90-deg Hybrid Erect-Image Prism Diagonal # EIDH90
  • GSO 0.965"/1.25" 90-deg Hybrid Erect-Image Prism Diagonal # EIDH90

Quick Overview

  • Economical 1.25" 90-deg prism diagonal for astronomical telescopes and spotting scopes
  • Produces upright and left-right corrected image for terrestrial viewing and convenient night-time viewing with star maps
  • Hybrid 0.965” - 1.25” configuration allows use of 1.25” eyepieces and accessories in vintage and low-cost telescopes with 0.965” focusers
  • Dual-step aluminum barrel also allows diagonal to fit directly into standard 1.25” focusers

Product Details

Important Note: Please note that the length of the 0.965" nosepiece, as listed below, is 15mm (0.59"). Before purchase, please make sure that the thumbscrew on your telescope is within this distance from the rear end of your focuser drawtube. Otherwise, the thumbscrew will not be able to engage and lock the diagonal. This is a known issue with some vintage telescopes in which the locking thumbscrew on the telescope is recessed by more than 0.6", and this diagonal will not work for you.

Disappointed by the lack of quality 0.965" eyepieces for your vintage telescope? Missing a diagonal for that small telescope you picked up in a garage sale? Wish you could use wider angle 1.25" eyepieces with your small spotting scope? Here's the solution you need!

Many vintage telescopes sold up to the 1960s, cheap introductory telescopes sold today, and many spotting scopes use a smaller, older, almost obsolete 0.965" diameter format for diagonals and eyepieces. Having a 0.965" barrel severely limits the number of eyepieces and accessories you can buy and use in the after-market.

This popular hybrid diagonal from GSO allows 1.25" eyepieces, diagonals, and other accessories to be used in 0.965" focusers, and at once allows hundreds of more common 1.25" format astronomy items to be used with your telescope.

GSO's hybrid 0.965"-1.25" 90-degree diagonal features an image erecting Amici glass prism that allows you to look into a telescope at a 90 degree angle. It produces an image that is oriented properly, which means that the image is upright and correct from left to right (i.e., a correct, non-inverted, non-reversed image). This is a great diagonal for daytime terrestrial use with small telescopes or spotting scopes. It can also be used for nighttime astronomy applications, especially when you would like to match the orientation of the star field with "correct" star maps and charts.

A unique feature of this hybrid diagonal is the use of a dual step 0.965"/1.25" chrome barrel on the telescope end. While designed primarily for use with 0.965" focusers, the step barrel also allows you to use this diagonal in 1.25" focusers (although your field of view might vignette in some situations if used in this manner). Total length of the nosepiece is 25mm (0.98"); length of 1.25" portion of nosepiece = 10mm (0.39"); length of 0.965" portion of nosepiece = 15mm (0.59").

The prism housing is made of high grade ABS plastic and the end barrels are made from precision machined aluminum. Weight: 3.7oz; 2 end caps included. Made in Taiwan.

Please Note: This diagonal can only be used with refractor telescopes and some catadioptric telescopes like Schmidt-Cassegrain, Maksutov-Cassegrain, etc. It not meant for use with Newtonian / Dobsonian reflector telescopes or other variants of Newtonian telescopes.