C90 - Binoculars CELESTRON - Free user manual and instructions

Product Type	Maksutov-Cassegrain Spotting Scope
Brand	Celestron
Model	C90
Model Number	52268
Aperture	90 mm (3.5 inches)
Focal Length	1250 mm
Focal Ratio	f/13.9
Optical Coatings	Multi-coated
Finder	8x21 Image Correcting Finder
Eyepiece Included	1.25 inch Plossl 32 mm (39x magnification)
Angular Field of View	1.3° (with 32 mm eyepiece)
Linear Field of View	68 ft @ 1000 yds / 23 m @ 1000 m
Eye Relief	20 mm
Near Focus	4.6 m (15 ft)
Length (with diagonal and eyepiece)	41 cm (16 in)
Weight (with diagonal and eyepiece)	2.3 kg (5 lb)
Mounting to Tripod	1/4 x 20 threaded hole (integrated tripod adapter)
Care and Cleaning	Use an optic cleaning kit; store in carrying case
Safety	Never look directly at the Sun; risk of eye damage
Warranty	Limited Lifetime Warranty (USA and Canada)
Optional Accessories	Additional 1.25 inch eyepieces, photo adapter, Celestron tripod

Frequently Asked Questions - C90 CELESTRON

How to install the eyepiece and image erecting diagonal?

Remove all rear covers. Loosen the thumbscrews on the optical tube and diagonal. Slide the chrome part of the diagonal onto the rear of the tube and tighten the screws. Then insert the eyepiece (32 mm) into the diagonal and tighten the screw. The 8x21 finder is installed similarly on the designated bracket.

How to focus the Celestron C90?

Turn the focus knob on the tube until the image is sharp. If the knob stops turning, turn it the other way. For a close object, turn clockwise; for a distant object, turn counterclockwise. Several rotations are needed to go from 4.6 m to infinity.

How to align the 8x21 finder?

Choose an object at least 457 m away. Center it in the main eyepiece (32 mm). Adjust the three small thumbscrews on the finder until the crosshairs are centered on the same object. If the finder image is blurry, turn the end of the finder eyepiece to focus.

What is the maximum useful magnification?

The maximum useful magnification is about 210x (60x per inch of aperture). For the C90, 3.5 inches x 60 = 210. However, the recommended range for bright images is 70x to 123x (20 to 35x per inch). Experiment to find the best setting.

How to calculate magnification with another eyepiece?

Divide the spotting scope's focal length (1250 mm) by the eyepiece focal length in mm. For example, with a 10 mm eyepiece, magnification is 1250/10 = 125x. Make sure to use compatible 1.25 inch eyepieces.

Can I mount a camera on the C90?

Yes. Remove the diagonal and eyepiece. Screw a specific T-ring onto the rear thread (integrated T-adapter). Then attach the SLR camera to the ring. For digital compacts, use the Celestron universal adapter (model 93626).

Which tripod to use?

The C90 has an adapter with 1/4 x 20 thread. Use a sturdy photo/video tripod. Celestron offers optional tripods. A stable tripod is essential for sharp images, especially at high magnification.

How to clean the optics?

Use an optic cleaning kit. Do not touch the lenses with your fingers. Store the spotting scope in its carrying case with caps in place to protect it. If necessary, follow the manufacturer's instructions.

What are important safety precautions?

Never look directly at the Sun, either with the naked eye or through the spotting scope. This can cause irreversible eye damage. Always remove the objective lens cover before use and use an appropriate solar filter if observing the Sun.

Is the warranty international?

Celestron's limited lifetime warranty applies to purchasers residing in the United States and Canada. For other countries, check the Celestron website for applicable warranty terms. Keep your proof of purchase.

USER MANUAL C90 CELESTRON

C90mm Maksutov Spotting Scope - #52268

Congratulations on your purchase of a Celestron spotting scope! Whether your interest is in sports, bird watching, nature, wildlife, casual astronomy, or other activities, this spotting scope offers very high optical quality to allow you years of viewing pleasure.

Assembly

To attach the Erect Image Diagonal and an Eyepiece:

1. Remove any caps from the rear of the optical tube, the erect image diagonal, and the eyepiece.
2. Loosen all thumbscrews on the rear part of the optical tube and the erect image diagonal so that the threads do not protrude into the barrels.
3. Slide the chrome portion of the erect image diagonal into the rear of the optical tube as shown in the left image below. Then, tighten the thumbscrews to hold the erect image diagonal in place.
4. Slide the chrome portion of the eyepiece (use the 32mm) into the erect image diagonal (see right image below). Then, tighten the thumbscrew to hold the eyepiece in place.
5. To use other eyepieces of varying powers, reverse the installation of the eyepiece above and install other eyepieces. Any 1.25" eyepiece will work with this spotting scope. Celestron offers a wide selection of optional eyepieces.

To attach the 8x21 Erect Image Finderscope:

The finderscope is an aid to locating objects to view as it is an 8 power instrument with a much wider field of view than the spotting scope itself. The finderscope itself comes pre-assembled and is mounted inside the bracket of the finderscope.

1. Loosen the thumbscrew on the mounting bracket on the optical tube (left image below).
2. Slide the finder bracket (with finderscope attached) into the mounting bracket on the optical tube (center image below).
3. The finderscope bracket will slide in from the back. The finderscope should be oriented so that the objective lens (larger piece of glass) is toward the front end of the spotting scope.
4. Tighten the thumbscrew on the mounting bracket to hold the finderscope firmly in place. The finderscope is correctly attached as shown in the right image below.

To Attach your Spotting Scope to a Photo/Video Tripod

Attach your spotting scope to a rigid photo/video tripod before trying to observe as the size and power of the spotting scope requires a solid tripod to be able to see sharp and steady views. On the bottom of the spotting scope is a tripod adapter (see image on pg. 1) which has 1/4 × 20 threaded holes and this will allow you to attach your tripod to the spotting scope. Celestron offers optional photo/video tripods.

Using your Spotting Scope

Prior to using your spotting scope, remove the front lens cap.

Warning Note: Never look directly at the Sun with the naked eye or with your spotting scope as eye damage may result.

Focusing

The C90 spotting scope focusing mechanism controls the position of the primary mirror which slides back and forth on the primary baffle tube. Turn the focusing knob (see image to the left and the knob is located in the bottom right area) until the image is sharp. If the knob will not turn, the primary mirror has reached the end of its travel on the focusing mechanism. Turn the knob in the opposite direction until the image is sharp. Once an image is in focus, turn the knob clockwise to focus on a closer object and counterclockwise for a more distant object. A single turn of the focusing knob moves the primary mirror only slightly. Therefore, it will take many turns to go from close focus (approximately 15 feet) to infinity. For astronomical viewing, out-of-focus star images are very diffuse making them difficult, if not impossible, to see. If you turn the focus knob too quickly, you can go right through focus without seeing the image. For best results, your first astronomical target should be a bright object (like the Moon) so that the image is visible even when out of focus.

Note: If changing eyepieces to use different powers on the same subject, you will have to refocus.

Aligning the Finderscope:

1. To make things a little easier, you should align the finderscope during the day when it is easier to locate objects.
2. Choose a conspicuous object that is over 500 yards away. This will eliminate any possible parallax effect
3. Point your spotting scope at the target and center it in the main optics of the spotting scope (using the 32mm eyepiece).
4. Check the finderscope to see where the object is located in the field of view.
5. Adjust the three small thumbscrews on the finder bracket, tightening one while loosening another, until the cross hairs are centered on the target

Accurate alignment of the finder will make it much easier to find objects in the main optical tube.

Note: If the image is not sharp (out of focus) with the finderscope, rotate the eyepiece end of the finderscope until you achieve a sharp focus.

Using different Eyepieces & Calculating Magnification

You can use different eyepieces to achieve different powers, field of views, etc.

To determine the magnification of your spotting scope, simply divide the focal length of the spotting scope by the focal length of the eyepiece used. In equation format, the formula looks like this:

Focal Length of Spotting scope (mm) Magnification = Focal Length of Eyepiece (mm)

Let's say, for example, you are using the 32mm Plossl eyepiece. To determine the magnification you simply divide the focal length of your spotting scope (1250mm) by the focal length of the eyepiece, 32mm. Dividing 1250 by 32 yields a magnification of 39 power.

Although the power is variable, each instrument under average skies has a limit to the highest useful magnification. The general rule is that 60 power can be used for every inch of aperture. For example, the C90 is 3.5 inches in diameter. Multiplying 3.5 by 60 gives a maximum useful magnification of 210 power. Although this is the maximum useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 70 to 123 times for the C90 spotting scope. Lower powers give you brighter images but experiment to see what is best for you.

Attaching a Camera

1. T-Adapter threads are built into the rear of the spotting scope (see right portion of image to the left). With a camera specific T-ring, a Digital SLR (or SLR) camera can be attached to the spotting scope.
2. Remove the erect image diagonal and eyepiece from the rear cell of the tube.
3. Thread the T-Ring onto the rear opening which contains the threads (T-Adapter) - see image to the left.
4. Mount your camera body onto the T-Ring the same as you would any other lens.

Note: Since digital cameras (not digital SLR cameras) do not use the T-system to mount cameras to lenses, spotting scopes, telescopes, etc. you need a different way to be able to use them to take photos. Celestron offers a Universal Digital Camera Adapter (Model # 93626) which makes it easy to attach most digital cameras to your spotting scope.

Maintenance

To protect your spotting scope when not being used, put on all lens covers and caps to keep the optics clean and then put the scope in its backpack. If your optics could use cleaning, use an optiese cleaning kit and follow the instructions.

SPECIFICATIONS		52268
	C90 Spotting Scope
Optical Design Maksutov-Cassegrain
Aperture
Focal Length 1250mm
Focal Ratio f/13.9
Optical Coatings Multi-Coated
Finderscope, Erect Image 8x21
Eyepiece - 1.25" Plossl		32mm (39x)
Angular Field of View	1.3° w/32mm
Linear FOV - ft@1000yds / m@1000m	w/32mm - 68/23
Eye Relief	20mm
Near Focus	15 feet (4.6m)
Length w/diagonal & eyepiece		16" (41cm)
Weight w/diagonal & eyepiece	5# (2.3Kg)
Note: Specifications subject to change without notice or obligation

Warranty

Celestron Spotting Scopes have the Celestron No Fault Limited Lifetime Warranty for the U.S.A. and Canadian customers. For complete details of eligibility and for warranty information on customers in other countries visit the Celestron website.

CELESTRON

2835 Columbia St.

Torrance, CA 90503 U.S.A.

www.ccelcstron.com ©2010 All Rights Reserved Printed in China 01-10

C90 mm Maksutov Spotting-Scope - 52268