Orion 9874 Using the Polar Axis Finder Scope, Alignment of the Polar Axis Finder Scope

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

Figure 8. 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).

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 8). The two stars at the end of the “bowl” of the Big Dipper point right to Polaris.

Observers in the Southern Hemisphere aren’t so fortunate to have a bright star so near the south celestial pole (SCP). The star Sigma Octantis lies about 1° from the SCP, but it is barely visible with the naked eye (magnitude 5.5).

For general visual observation, an approximate polar align‑ ment is sufficient.

1.Level the equatorial mount by adjusting the length of the three tripod legs. For your safety, remove the optical tube and counterweights when doing this.

2.There are two altitude adjusting L-bolts (see Figure 7); loosen one while tightening the other. By doing this you will adjust the latitude of the mount. Continue adjusting the mount until the pointer on the latitude scale is set at the latitude of your observing site. If you don’t know your lati‑ tude, consult a geographical atlas to find it. For example, if your latitude is 35° North, set the pointer to 35. The lati‑ tude setting should not have to be adjusted again unless you move to a different viewing location some distance away.

3.Loosen the Dec. lock lever and rotate the telescope’s opti‑ cal tube until it is parallel with the right ascension axis, as it is in Figure 7.

4.Move the tripod so the telescope tube and right ascen‑ sion axis point roughly at Polaris. If you cannot see Polaris directly from your observing site, consult a compass and rotate the tripod so the telescope points north.

The equatorial mount is now polar aligned for casual observ‑ ing. More precise polar alignment is recommended for astro­ photography. For this we recommend using the optional polar axis finder scope

From this point on in your observing session, you should not make any further adjustments to the latitude of the mount,

Eyepiece	Alignment	Focus	Objective
focus ring	setscrew (3)	lock ring	lens

Figure 9. The optional polar axis finder scope.

nor should you move the tripod. Doing so will undo the polar alignment. The telescope should be moved only about its R.A. and Dec. axes.

Using the Polar Axis Finder Scope

The Atlas EQ mount comes with a polar axis finder scope (Figure 9) housed inside the right ascension axis of the mount. When properly aligned and used, it makes accurate polar alignment quick and easy to do.

Alignment of the Polar Axis Finder Scope

1.Loosen the Dec. lock lever and rotate the optical tube on the declination axis so that the tube is at a 90° to the right ascension axis (Figure 10). Tighten the Dec. lock lever.

2.Look through the polar finder at a distant object (during the day) and center it on the crosshairs. You may need to adjust the latitude adjustment L-bolts and the tripod posi‑ tion to do this.

3.Rotate the mount 180° about the R.A. axis. It may be con‑ venient to remove the counterweights and optical tube first.

4.Look through the polar finder again. Is the object being viewed still centered on the crosshairs? If it is, then no further adjustment is necessary. If not, then look through the polar finder while rotating the mount about the R.A. axis. You will notice that the object you have previously centered moves in a circular path. Use the three alignment setscrews on the polar axis finder (Figure 9) to redirect the crosshairs of the polar finder to the apparent center of this circular path. Repeat this procedure until the position that the crosshairs point to does not rotate off-center when the mount is rotated in R.A.

The polar axis finder scope is now ready to be used. When not in use, replace the plastic protective cover to prevent the polar finder from getting bumped.

Using the Polar Axis Finder Scope

The reticle of the polar axis finder scope for the Atlas has a tiny star map printed on it that makes precise polar alignment

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