Orion 9968 Viewing with Eyeglasses, Aligning the Finder Scope, Focusing the finder scope, 1800mm

View through finder scope

View through the SkyView Pro 150mm EQ

Figure 5. Images through the finder scope will appear upside- down and backwards (rotated 180°). Images through the SkyView Pro 150mm EQ with its diagonal in place will be reversed from left- to right.

a star diagonal. The finder scope view will be rotated 180° (see Figure 5).

If you have trouble focusing, rotate the focus knob counter- clockwise as far as it will go. Look through the eyepiece while slowly rotating the focus knob clockwise.You should soon see the point at which focus is reached.

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 por‑ tion of the full field. If they do, you can easily observe with your glasses off by just re-focusing the telescope by 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 SkyView Pro 150mm EQ comes with a 8x40 achromatic finder scope (Figure 3a). The number 8 means eight-times

Turn the focus knob until the object is properly focused. Make sure to position the object in the center of the telescope’s eye‑ piece by turning the R.A. and declination slow-motion control knobs (the R.A. and Dec. lock levers must be tightened to use the slow-motion control knobs).

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

magnification and the 40 indicates a 40mm diameter front lens. The finder scope makes it easier to locate the subject

Eyepiece Focal Length

= Magnification

you want to observe in the telescope, because the finder scope has a much wider field of view.

The SkyView Pro 150mm EQ has a focal length of 1800mm, which when used with the supplied 25mm eyepiece yields:

1800mm

The finder scope uses a spring-loaded bracket that makes alignment of the finderscope very easy. As you turn either of

25mm

= 72x

the thumbscrews, the spring in the bracket’s tensioner moves in and out to keep the finder scope secure in the bracket.

The magnification provided by the 10mm eyepiece is:

1800mm

The finder scope must be aligned accurately with the tele‑ scope for proper use. To align it, first aim the main telescope

10mm

= 180x

at an object at least a 1/4 mile away—the top of a telephone pole, a chimney, etc. First, loosen the R.A. and Dec. lock levers and move the telescope until it is pointing towards the desired object. Then sight along the tube to aim the telescope.

The maximum attainable magnification for a telescope is directly related to how much light it can gather. The larger the aperture, the more magnification is possible. In general a fig‑ ure of 2x per millimeter of aperture is the maximum attain‑

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