Celestron C90 MAK Manuel D'instructions page 2

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 1/4x20 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:
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 32 mm 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:
Magnification =
Let's say, for example, you are using the 32 mm Plossl eyepiece. To determine the magnification you simply divide the focal length of your spotting
scope (1250 mm) by the focal length of the eyepiece, 32 mm. Dividing 1250 by 32 yields a magnification of 39 power.
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.
Focal Length of Spotting scope (mm)
Focal Length of Eyepiece (mm)