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IN 011 Rev. C 03/09

Orion Tele-Extender

#5125

 Standard Tele-Extender

#5127

 Variable Tele-Extender

Your Orion Tele-Extender will allow you to take high magnifica-
tion photographs of celestial objects with a Schmidt-Cas segrain 
telescope. It is particularly useful for planetary astro-photogra-
phy, close-ups of lunar craters, and extremely long distance 
terrestrial photography. 

How To Use The Orion Tele-Extender  

The Standard Tele-Extender (A) is a fixed-length extension 
tube, which produces a fixed magnification for a given eye-
piece used with the tele-extender. The Variable Tele-Extender 
(B) has an adjustable-length extension tube, allowing magni-
fication to be changed without switching eyepieces. 
For high-powered photography through your Schmidt-
Cassegrain, attach the visual back in the normal manner. Instead 
of inserting the star diagonal into the visual back, insert an eye-
piece and hand tighten the set screw. Thread the tele-extender 
onto the visual back, over the eyepiece. Thread your T-ring onto 
the end of the tele-extender and attach your camera. 
Some telescopes do not have a separate visual back, such as the 
Meade LX5 series, LX6, and the Meade 2045. You may have to 
purchase a visual back to use a tele-extender. A 1.25" visual back 
which fits Meade and Celestron Schmidt-Cassegrain 4", 8", 10", 
11", and 14" scopes is available from Orion (#15048). (Celestron 

C-90s and some other small spotting scopes have threads that 
will fit a tele-extender directly but require the use of .965" eye-
pieces to create the higher magnifications.) 
Most standard eyepieces are useable with a tele-extender. 
Some eyepieces have barrel assemblies that are too large to 

fit inside a tele-extender. See the diagram below for reference 
on how to attach a tele-extender to your telescope.
When you look through your camera and focus the telescope, 
you will notice a dim, highly magnified image. This is normal 
when using a tele-extender. The eyepiece enlarges the image 
and therefore reduces the amount of light. Shorter-focal-length 
eyepieces magnify the image more, causing it to be dimmer. 
Dimmer images mean longer exposure times will be necessary.

Focusing 

It can be quite difficult to focus the telescope, especially when 
using eyepiece projection! In fact, with most cameras the 
image in the viewfinder can be so dim that it may be difficult to 
find the focal point at all. Use a bright object such as the Moon 
or a bright star for focusing. Find and center this object in the 
telescope’s field before installing the camera adapter. 

Tele-Extender Effective Focal Length Chart

Below is a chart of effective focal lengths and f/ratios to assist 
you in determining the best combinations for your system. 
Values are rounded to the nearest 5 or 0 for convenience. For 
the variable tele-extender, the effective focal length below 
applies when the unit is fully extended. Shortening the vari-
able tele-extender will reduce the effective focal length.

Instrument 

8" f/10 

10" f/10  11"f/10

Base Focal Length  2000mm  2500mm  2800mm

Eyepiece

40mm 

7000mm f/35 

8700mm f/35 

9800mm f/35

30mm 

9500mm f/50 

1200mm f/50 

13100mm f/50

25mm 

12000mm f/60 

14000mm f/60 

15700mm f/60

20mm 

14000mm f/70 

17800mm f/70 

19600mm f/70

18mm 

18000mm f/90 

12000mm f/90 

21777mm f/80

15mm 

19000mm f/95 

24000mm f/95 

26500mm f/100

13mm 

*22000mm f/115 

28000mm f/110 

30600mm f/115

12mm 

*28500mm f/140 

*30000mm f/140 

*33000mm f/125

10mm 

*29000mm f/140 

*36000mm f/145 

*40600mm f/150

9mm 

*39000mm f/190 

*40300mm f/165 

*45000mm f/165

7mm 

*41000mm f/210 

*52000mm f/210 

*58000mm f/215

*Beyond useful magnification—not recommended 

Schmidt-Cassegrain

Visual Back

Eyepiece

Tele-Extender

T-Ring

Camera

A.

B.

Corporate Offices:

 89 Hangar Way, Watsonville CA 95076 - USA

Toll Free USA & Canada:

 (800) 447-1001 

International:

 +1(831) 763-7000

Customer Support:

 [email protected]

Copyright © 2021 Orion Telescopes & Binoculars. All Rights Reserved. No part of this product instruction or any of its contents 

may be reproduced, copied, modified or adapted, without the prior written consent of Orion Telescopes & Binoculars.

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INSTRUCTION MANUAL

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