Celestron CGEM DX Mount and Tripod Computerized Telescope CGEM DX Mount Manual - Page 21

The constant, mentioned above, is a relationship between your latitude and the angular distance the celestial pole is above the northern (or southern) horizon; The angular distance from the northern horizon to the north celestial pole is always equal to your latitude. To illustrate this, imagine that you are standing on the north pole, latitude +90°. The north celestial pole, which has a declination of +90°, would be directly overhead (i.e., 90 above the horizon). Now, let's say that you move one degree south - your latitude is now +89° and the celestial pole is no longer directly overhead. It has moved one degree closer toward the northern horizon. This means the pole is now 89° above the northern horizon. If you move one degree further south, the same thing happens again. You would have to travel 70 miles north or south to change your latitude by one degree. As you can see from this example, the distance from the northern horizon to the celestial pole is always equal to your latitude. If you are observing from Los Angeles, which has a latitude of 34°, then the celestial pole is 34° above the northern horizon. All a latitude scale does then is to point the polar axis of the telescope at the right elevation above the northern (or southern) horizon. To align your telescope: 1. Make sure the polar axis of the mount is pointing due north. Use a landmark that you know faces north. 2. Level the tripod. There is a bubble level built into the mount for this purpose. 3. Adjust the mount in altitude until the latitude indicator points to your latitude. Moving the mount affects the angle the polar axis is pointing. For specific information on adjusting the equatorial mount, please see the section "Adjusting the Mount." This method can be done in daylight, thus eliminating the need to fumble around in the dark. Although this method does NOT put you directly on the pole, it will limit the number of corrections you will make when tracking an object. It will also be accurate enough for short exposure prime focus planetary photography (a couple of seconds) and short exposure piggyback astrophotography (a couple of minutes). All-Star Polar Align The CGEM DX mount has a polar alignment function called "All-Star" polar alignment that will help you polar align your telescope for increased tracking precision and astrophotography. This feature allows you to choose any bright alignment star to assist in accurately aligning your telescope's mount with the North Celestial Pole. Before using the Polar Align feature, the scope must first be roughly pointed towards North and should be aligned with two stars in the sky. See the "Latitude Scale" section for help with finding north and adjusting the mounts latitude. Once your telescope is aligned on two stars and at least one additional calibration star, slew the telescope to any bright star in its Named Star database list. For best results choose a polar alignment star that is high in the sky and near the Meridian. Try to avoid stars that are close to the west/east horizon, directly overhead or too near the celestial pole. Once there, press the Align button and use the Up/Down buttons on the hand controller to select Polar Align from the list. The Polar Align feature has two options: Align Mount - After performing a two star alignment and slewing your telescope to any bright star in the telescope's database, select the "Align Mount" option. The telescope will then re-slew to the same star. 1. Center the star in the finderscope and press ENTER. 2. Then accurately center the star in your eyepiece and press ALIGN. The telescope will then "sync" on this star and slew to the position that the star should be if it were accurately polar aligned. For the most accurate alignment it is best to use a reticle eyepiece (see Optional Accessories) or a high power eyepiece to precisely center the star in the field of view. 3. Use the mounts latitude and azimuth adjustments (see figure 2-10) to place the star in the center of the eyepiece. Do not use the direction buttons on the hand control to position the star. Once the star is centered in the eyepiece, press ENTER; the polar axis should now be pointed towards the North Celestial Pole. Updating your Star Alignment After polar alignment it's a good idea to check the pointing accuracy of the telescope to see how much it may have been affected by moving the mount. Since the polar alignment process requires you to "sync" the telescope on a bright star before you begin, it will be necessary to undo the sync before re-aligning. To undo the sync: 1. Press the Align button and use the Up/Down buttons on the hand controller to select Undo Sync from the list, and press Enter. The message Complete will display on the LCD. To re-align your telescope: 2. Slew the telescope to one of the original alignment stars, or another bright star if the original alignment stars are no longer in a convenient location. Press the Align button and use the Up/Down buttons on the hand controller to select Alignment Stars from the list. 3. The hand control will ask you which of the original alignment stars you wish to replace. Use the Up/Down buttons to select the desired star and press Enter. 4. Once again center the star in the finderscope and press Enter. 5. Then center the star in the eyepiece and press Align. 6. Repeat the process on a second alignment star. For additional all sky pointing accuracy, it's a good idea to align on at least one additional calibration star located on the opposite side of the Meridian. To add calibration stars: 1. Slew the telescope to a bright star on the opposite of the Meridian from your two alignment stars. 2. Press the Align button and use the Up/Down buttons on the hand controller to select Calib. Stars from the list, and press Enter. 3. Align the star in the finderscope and then the eyepiece as you did with the alignment stars. Display Align - the user can now display the polar alignment error in the RA and DEC axes. These values show how close the mount is pointed at the celestial pole base on how accurately the user centered the alignment star with the hand control and with the mount adjustment. To display the alignment error: 1. Press the Align button and use the Up/Down buttons on the hand controller to select Display Align from the list, and press Enter. Pointing at Polaris This method of Polar aligning utilizes Polaris as a guidepost to the celestial pole. Since Polaris is less than a degree from 19