Orion 9874 Using Your Telescope, Focusing the Telescope, Viewing with Eyeglasses

Naked-eye view

View through finder scope and telescope

Figure 6. The view through a standard finder scope and reflector telescope is rotated 180°. This is true for the Atlas 10 EQ and its finder scope as well.

5. Using Your Telescope

Focusing the Telescope

With the 25mm eyepiece inserted in the focuser, loosen the R.A. and Dec.lock levers and move the telescope so the front (open) end is pointing in the general direction of an object at least 1/4-mile away. Now, with your fingers, slowly rotate one of the focusing knobs until the object comes into sharp focus. Go a little bit beyond sharp focus until the image just starts to blur again, then reverse the rotation of the knob, just to make sure you’ve hit the exact focus point.

NOTE: The image in the telescope will appear rotated 180° (upside down and reversed left-to-right). This is nor- mal for astronomical scopes. The finder scope view will also be rotated 180° (see Figure 6).

If you have trouble focusing, rotate the focusing knob so the drawtube is in as far as it will go. Now look through the eyepiece while slowly rotating the focusing knob in the opposite direction. You should soon see the point at which focus is reached.

The black nylon thumbscrew on the top of the body of the focuser (see Figure 4) will lock the focuser drawtube in place once the telescope is properly focused. Before focusing, remember to first loosen this thumbscrew.

Viewing with Eyeglasses

If you wear eyeglasses, you may able to keep them on while you observe, if the eyepiece has enough “eye relief” to allow you to see the whole field of view. You can try this by looking through the eyepiece first with your glasses on, and then with them off, and see if the glasses restrict the view to only a portion of the full field. If they do, you can easily observe with your glasses off by just re-focusing the telescope the needed amount. If you suffer from severe astigmatism, however, you may find images noticeably sharper with your glasses on.

Aligning the Finder Scope

The Atlas 10 EQ Deluxe comes with a 9x50 achromatic finder scope (Figure 3a). The number 9 means six-times magnifica‑

tion and the 50 indicates a 50mm diameter front lens. The finder scope makes it easier to locate the object you want to observe in the telescope, because the finder scope has a much wider field-of-view.

The Atlas 10 EQ’s finder scope uses a spring-loaded bracket that makes alignment of the finderscope very easy. As you turn either of the thumbscrews, the spring in the bracket’s ten‑ sioner moves in and out to keep the finder scope secure in the bracket.

The finder scope must be aligned accurately with the tele‑ scope for proper use. To align it, first aim the main telescope in the general direction of an object at least a 1/4 mile away— the top of a telephone pole, a chimney, etc. Loosen the R.A. and Dec. lock levers and move the telescope until it is pointing toward the desired object. Then sight along the tube to pre‑ cisely aim the telescope. Turn the focus knob until the object is properly focused. Retighten the lock levers.

Now look in the finder scope. Is the object visible? Ideally it will be somewhere in the field of view. If not, some coarse adjustment to the finder scope bracket’s alignment thumb‑ screws will be needed until the object comes into the finder scope’s field of view.

With the image in the finder scope’s field of view, you now need to fine-adjust the alignment thumbscrews to center the object on the intersection of the crosshairs. Adjust the aim of the finder scope by turning the thumbscrews, one at a time, until the object is centered.

The finder scope alignment needs to be checked before every observing session. This can easily be done at night, before viewing through the telescope. Choose any bright star or planet, center the object in telescope eyepiece, and then adjust the finder scope bracket’s alignment thumbscrews until the star or planet is centered on the finder’s crosshairs.

Focusing the finder scope

If, when you look through the finder scope, the images appear somewhat out of focus, you will need to refocus the finder scope for your eyes. Loosen the lock ring located behind the objective lens cell on the body of the finder scope (see Figure 3a). Back the lock ring off by a few turns, for now. Refocus the finder scope on a distant object by threading the objec‑ tive lens cell in or out of the finderscope body. Precise focus‑ ing will be achieved by focusing the finder scope on a bright star. Once the image appears sharp, retighten the locking ring behind the objective lens cell. The finder scope’s focus should not need to be adjusted again.

Magnification & Eyepieces

Magnification, or power, is determined by the focal length of the telescope and the focal length of the eyepiece. Therefore, by using eyepieces of different focal lengths, the resultant magnification can be varied.

Magnification is calculated as follows:

Telescope Focal Length (mm) = Magnification

Eyepiece Focal Length (mm)

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