Orion 9968 instruction manual Setting Up and Using the Equatorial Mount, Polar Alignment

Dec. slow-motion control knob

Dec. setting‑circle

Front opening

			(R	Right
			Ascension
			.	.
				)
		) axis		axis
	(Dec	.
Declination

R.A. setting‑circle

Polar axis finder (optional)

Latitude scale

Latitude adjustment

L-bolts

a.b.

Figure 6a-b.The SkyView Pro 150mm EQ mount.

Dec. lock lever

R.A. lock lever

R.A. slow-motion control knob

able for most telescopes. Your SkyView Pro 150mm EQ has an aperture of 150 millimeters, so the maximum magnification would be about 300x. This level of magnification assumes you have ideal conditions for viewing.

Keep in mind that as you increase magnification, the bright‑ ness of the object viewed will decrease; this is an inherent principle of the laws of physics and cannot be avoided. If mag‑ nification is doubled, an image appears four times dimmer. If magnification is tripled, image brightness is reduced by a factor of nine!

Always start with your lowest power eyepiece and work your way up. Start by centering the object being viewed in the 25mm eyepiece. Then you may want to increase the magni‑ fication to get a closer view. If the object is off-center (i.e., it is near the edge of the field of view) you will lose it when you increase magnification since the field of view will be narrower with the higher-powered eyepiece. To change eyepieces, first loosen the securing thumbscrews on the diagonal. Then care‑ fully lift the eyepiece out of the holder. Do not tug or pull the eyepiece to the sides, as this will knock the telescope off its target. Replace the eyepiece with the new one by sliding it gently into the holder. Re-tighten the diagonal thumbscrews, and refocus­ for your new magnification.

	Little Dipper
	(in Ursa Minor)
Big Dipper	N.C.P.
(in Ursa Major)		Polaris
Pointer		Cassiopeia
Stars

Figure 7. To find Polaris in the night sky, look north and find the Big Dipper. Extend an imaginary line from the two "Pointer Stars" in the bowl of the Big Dipper. Go about five times the distance between those stars and you'll reach Polaris, which lies within 1° of the north celestial pole (NCP).

from drifting out of your telescope’s field of view while you’re observing.

This is accomplished by slowly rotating the telescope on its right ascension axis, using only the R.A. slow-motion knob. But first the R.A. axis of the mount must be aligned with the Earth’s rotational (polar) axis—a process called polar alignment.

6.Setting Up and Using the Equatorial Mount

When you look at the night sky, you no doubt have noticed that the stars appear to move slowly from east to west over time. That apparent motion is caused by the Earth’s rotation (from west to east). An equatorial mount (Figure 6) is designed to compensate for that motion, allowing you to easily “track” the movement of astronomical objects, thereby keeping them

Polar Alignment

For Northern Hemisphere observers, approximate polar align‑ ment is achieved by pointing the mount’s right ascension axis at the North Star, or Polaris. It lies within 1° of the north celes‑ tial pole (NCP), which is an extension of the Earth’s rotational axis out into space. Stars in the Northern Hemisphere appear to revolve around the NCP.

To find Polaris in the sky, look north and locate the pattern of the Big Dipper (Figure 7). The two stars at the end of the “bowl” of the Big Dipper point right to Polaris.

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