Orion 9995 instruction manual Alignment of the Polar Axis Finder Scope

To find Polaris in the sky, look north and locate the pattern of the Big Dipper (Figure 6). 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.

2.There are two latitude adjustment L-bolts (see Figure 5); 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 latitude 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 5.

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 observing. More precise polar alignment is recommended for astropho- tography. For this we recommend using the 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, nor should you move the tripod. Doing so will undo the polar align- ment. The telescope should be moved only about its R.A. and Dec. axes.

The Polar Axis Finder Scope

The Sirius EQ-G mount comes with a polar axis finder scope (Figure 7) housed inside the right ascension axis of the mount. When properly aligned and used, it makes accurate polar alignment quick and easy to do. Unthread the cover at the rear of the mount’s right ascension axis and remove the cap on the front opening of the equatorial mount (Figure 5) to view through the polar axis finder scope.

Alignment of the Polar Axis Finder Scope

1.Loosen the Dec. lock lever and rotate the optical tube on the declination axis until you have a clear view through the polar axis finder scope (Figure 8). Tighten the Dec. lock lever.

2.Look through the polar finder at a distant object (during the day) and center it in the crosshairs. You may need to adjust the latitude adjustment L-bolts and the tripod position to do this. Focus the polar finder by rotating the eyepiece.

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

Figure 7. The polar axis finder scope.

Objective lens of polar axis finder scope

Figure 8. The optical tube must be rotated about the Dec. axis until you have a clear view along the R.A. axis with the polar axis finder scope.

3.Rotate the mount 180° about the R.A. axis. It may be con- venient to remove the counterweights and optical tube before doing this.

4.Look through the polar finder again. Is the object being viewed still centered on the crosshairs? If it is, then no fur- ther 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 set- screws on the polar axis finder (Figure 7) to redirect the crosshairs of the polar finder to the apparent center of this circular path.

5.Repeat this procedure until the position 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.

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