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 magnica-
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 xed-length extension
tube, which produces a xed magnication for a given eye-
piece used with the tele-extender. The Variable Tele-Extender
(B) has an adjustable-length extension tube, allowing magni-
cation 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 ts 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 t a tele-extender directly but require the use of .965" eye-
pieces to create the higher magnications.)
Most standard eyepieces are useable with a tele-extender.
Some eyepieces have barrel assemblies that are too large to
t 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 magnied 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 viewnder can be so dim that it may be difficult to
nd 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 eld 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 magnication—not recommended
Schmidt-Cassegrain
Visual BackEyepieceTele-ExtenderT-RingCamera
A.
B.
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