Orion 9738 guide

The reticle of the polar axis finder scope has a tiny star map printed on it that makes precise polar alignment quick and easy. If you do not have a clear view of Polaris from your

Figure 11. The optical tube must be at a 90° angle to the right ascension axis in order to view through the polar axis finder

observing site, you will not be able to use the polar-axis finder to precisely polar align the telescope.To align the mount using the polar axis finder scope, follow these instructions:

1.Approximately polar-align the mount as outlined in the pro- cedure earlier.

2.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 11). Tighten the Dec. lock lever.

Remove the cap on the front opening of the equatorial mount (Figure 7). Focus the polar finder by rotating the eyepiece. Now, sight Polaris in the polar axis finder scope. If you have followed the approximate polar alignment procedure accurate- ly, Polaris will probably be within the field of view. If not, move the tripod left-to-right, and adjust the latitude up-and down until Polaris is somewhere within the field of view of the polar axis finder scope.

Shine a red flashlight down the front end of the polar finder to illuminate the reticle within the field of view. Make sure the flashlight shines in at an angle, so as not to block the polar finder’s field of view. It may be helpful to have a friend hold the flashlight while you look through the polar finder. Note the con- stellation Cassiopeia and the Big Dipper in the reticle. They do not appear to scale, but they indicate the general posi- tions of Cassiopeia and the Big Dipper relative to the north celestial pole (which is indicated by the cross at the center

of the reticle). Rotate the reticle so the constellations depict- ed match their current orientation in they sky when viewed with the naked eye. To do this, release the R.A. lock lever and rotate the main telescope around the R.A. axis until the reticle is oriented with sky. For larger optical tubes, you may need to remove the tube from the mount to prevent it from bumping into the mount. Once the reticle is correctly oriented, use the right ascension lock lever to secure the mount’s position.

Now use the azimuth adjustment knobs (Figure 9) and the latitude adjustment L-bolts (Figure 7) on the mount to position the star Polaris inside the tiny circle marked “Polaris” on the finder’s reticle. You must first loosen the knob underneath the equatorial mount on the center support shaft to use the azi- muth adjustment knobs. Once Polaris is properly positioned within the reticle, you are precisely polar aligned.

Note: From this point on in your observing session, you should not make any further adjustments in the azimuth or the latitude of the mount, nor should you move the tripod. Doing so will undo the polar alignment. The tele- scope should be moved only about its right ascension and declination axes.

Additional Note Regarding Focusing the Polar Axis Finder Scope

The polar axis finder scope is normally focused by simply rotating the eyepiece focus ring. However, if after adjusting the focus ring you find that the image of the reticle is sharp, but the stars are out of focus, then you must adjust the focus of the polar axis finder’s objective lens. To do this, first remove the polar axis finder from the mount. Look through the polar axis finder at a star (at night) or distant object at least 1/4 mile away (during daylight). Use the eyepiece focus ring to bring the reticle into sharp focus. Now, loosen the focus lock ring (Figure 10a) and thread the entire objective end of the finder inwards or outwards until images appear sharp. Re-tighten the focus lock ring. Once the polar axis finder’s objective lens is focused, it should not need to be adjusted again.

Use of the Right Ascension and Declination Slow- Motion Control Knobs

The right ascension (R.A.) and declination (Dec.) slow-motion control knobs allow fine adjustment of the telescope’s position to center objects within the field of view. Before you can use the knobs, you must manually “slew” the mount to point the telescope in the vicinity of the desired target. Do this by loos- ening the R.A. and Dec. lock levers and moving the telescope about the mount’s right ascension and declination axes. Once the telescope is pointed close to the object to be viewed, retighten both lock levers.

The object should now be visible somewhere in the telescope’s finder scope. If it isn’t, use the slow-motion knobs to scan the surrounding area of sky. When the object is visible in the finder scope, use the slow-motion knobs to center it. Now, look in the telescope’s eyepiece. If the finder scope is properly aligned, the object should be visible somewhere in the field of view. Once the object is visible in the eyepiece, use the slow-motion knobs to center it in the field of view.