Celestron C90 Instruction Manual - Page 7

Browse online or download pdf Instruction Manual for Telescope Celestron C90. Celestron C90 17 pages. Multipurpose instrument
Also for Celestron C90: User Manual (9 pages), Operating Manual (16 pages)

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Remove the eyepiece currently in the spotting scope.

Insert a new eyepiece into the 45° Erect Image Diagonal.

Tighten the thumbscrew on the 45° Erect Image Diagonal to hold the eyepiece in place

With the new eyepiece in place you will need to refocus your C90 (unless the eyepieces have the same

focus point, something known as being parfocal). Once again, turn the focusing ring until the image is

sharp.

You can upgrade your Model # 81031 to use 1-1/4" eyepieces by purchasing the Erect Image Diagonal

(#94113-A). The larger diameter eyepieces allows you a wider field of view and better eye relief.

Celestron offers a wide variety of eyepieces as optional accessories. To determine the magnification of

each eyepiece used with your C90 spotting scope, see the section "Calculating Magnification" at the end of

this manual.

In addition to eyepieces, you may also use a Barlow lens to increase magnification. A Barlow lens is a

negative lens that increases the focal length of a spotting scope. Used with an eyepiece it increases the

magnification. The amount of the increase depends on the lens itself and its position in the optical system.

Celestron offers one Barlow lens designed for use with .96" systems (#93502) and two for the 1-1/4"

systems (#93506 & #93507).

Aligning the Finderscope

The C90 comes with an 8x20 finderscope to help you locate distant objects that might be overlooked in the

narrow field of the main optics. The finder is attached and aligned at the Celestron factory. However, if the

finder becomes misaligned, use the following procedure to align it:

Choose a target in excess of one mile away. This will eliminate any possible parallax effect.

Point the C90 at your target and center it in the main optics of the spotting scope.

Adjust the screws on the finder bracket until the cross hairs in the finder are centered on the target.

Tighten each screw a quarter of a turn so they will not come loose.

Using Your C90 Photographically

Your C90 can be used photographically as well as visually. To turn your C90 into a 1000mm telephoto lens

all you need is a C90 T-Adapter (#93635-A) and a T-Ring for your particular camera make (i.e., Nikon,

Minolta, Pentax, etc.). The T-Ring replaces the 35mm SLR camera's normal lens.

Attaching a Camera

To attach a camera to your C90:

1. Remove all visual accessories.

2. Thread the T-Ring onto the T-Adapter.

3. Mount your camera body onto the T-Ring the same as you would any other lens.