Meade ETX-90 User Manual - Page 9

ALIGNING THE ETX90 Aligning the ETX90 To automatically track and locate objects in the night sky, the ETX90 must first be aligned on the sky. It is best to set up the telescope in twilight or before sunset the first time you use the ETX90. Setup the telescope in a large open area where you can see lots of the night sky. Make sure the ground is stable and approximately level. It is best to setup the scope away from bright nighttime lighting. Bright lights will spoil your night vision and impede you ability to see the sky. The ETX "Alt/Az" Home Position Once the ETX90 is fully assembled, you will first need to initialize AutoStar, set the telescope into the home position, and perform the Easy Alignment in order for the ETX90 to successfully locate celestial objects. True North Telescope Tube is level Figure 1: Alt/Az Home Position The home position for the ETX90 is with the telescope optical tube level and pointed in the direction of True North. See Figure 1. Correct telescope placement in the home position will ensure the successful location of the alignment stars. Finding True North Method #1: Finding True North using the North Star (Polaris): To find True North, insert the bubble level/compass into they eyepiece holder and point the telescope tube towards Magnetic North. See the "Locating Polaris" diagram below, which directs you to the North Star (Polaris). Looking towards Magnetic North locate the Big Dipper; follow the two stars in the bowl of the Big Dipper to the North Star. With the tube Little Dipper Polaris still level, rotate it so that it points in the direction of the North Star. Lock the horizontal lock. The tube is pointing True North and now in the Alt/Az home position. Method #2: Finding True North using a compass adjusted for local declination: True North and Magnetic North differ and will vary from location to location. In order to correctly compensate for these differences you will need to know the declination based on you location. Find your location on the declination map of North America on page 56, Appendix G, or the world map on page 57, Appendix H. Notice the curved contour lines that are referenced with plus (+) and minus (-) values. Notice the thicker line in the middle of the map that has a value of zero. Along this line, Magnetic North will point to True North; no compensation will be necessary. Most of us are not so lucky and will have to compensate using the declination value for our location. For those of you that live on the left side of the thicker zero (0) value line your declination values will have positive (+) values and said to be East Declination. Those of you located to the right will have negative (-) values and said to be West Declination. For example if you were located in San Francisco, your East Declination value would be about 14 1/2 (San Francisco is located between the 14 and 15 lines). Using this value, Magnetic North would be 14 1/2 degrees East of True North and you would align your telescope tube along this line. Use the AutoStar left arrow slew button to rotate the telescope counterclockwise until the compass needle is on the 14 1/2 line. If you were located in New York City, your West Declination value would be about -13. Using this value, Magnetic North would be minus (-) 13 degrees West of True North or 347° (360° - 17° = 347°) and you would align your telescope tube along this line. Using the AutoStar right arrow slew button to rotate the telescope clockwise until the compass is ont eh 13° line. Lock the Compass needle is pointing to Magnetic North Big Dipper Locating Polaris Cassiopeia Figure 2: Bubble Level/Compass Bubble is centered