Celestron CPC Deluxe 800 HD Computerized Telescope CPC Deluxe HD Manual - Page 23

>> Polar Alignment (with optional Wedge) Even though the CPC can precisely track a celestial object while in the Alt-Az position, it is still necessary to align the polar axis of the telescope (the fork arm) to the Earth's axis of rotation in order to do long exposure astrophotography. To do an accurate polar alignment, the CPC requires an optional equatorial wedge between the telescope and the tripod. This allows the telescope's tracking motors to rotate the telescope around the celestial pole, the same way as the stars. Without the equatorial wedge, you would notice the stars in the eyepiece would slowly rotate around the center of the field of view. Although this gradual rotation would go unnoticed when viewing with an eyepiece, it would be very noticeable when imaging. Polar alignment is the process by which the telescope's axis of rotation (called the polar axis) is aligned (made parallel) with the Earth's axis of rotation. Once aligned, a telescope with a clock drive will track the stars as they move across the sky. The result is that objects observed through the telescope appear stationary (i.e., they will not drift out of the field of view). If not using the clock drive, all objects in the sky (day or night) will slowly drift out of the field. This motion is caused by the Earth's rotation. >> All-Star Polar Alignment The CPC hand control 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 stars to assist in accurately aligning your telescope and wedge with the North Celestial Pole. Before using the Polar Align feature, you must first perform an EQ North or South Alignment. Once your telescope is EQ aligned, slew the telescope to any bright star in its Named Star database list. This will be the star used for the All-Star Polar Alignment. For best results, it is always good to 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. 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 Wedge and Display Align. Align Wedge - After performing an EQ North or South Alignment and slewing your telescope to any bright star in the telescope's database, select the "Align Wedge" 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 wedges latitude and azimuth adjustments 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. FIGURE 6-3 This is how the telescope is to be set up for polar alignment. The tube should be parallel to the fork arm and the mount should point to Polaris. 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. 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 based 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. >> www.celestron.com 21