Meade LX850-ACF 10 inch User Manual - Page 24

AutoStar #G4et9t7inHgASNtDarBtOedX AutoStar used during the alignment procedure). Press the GOTO key to choose that star. 5. The telescope will slew to that star. When slewing has been completed, re-center the star in the eyepiece or camera. Then hold the "ENTER" key for 2 seconds. Then press "ENTER" again to confirm your position. StarLock will now compensate for the offset. Test your Collimation Before collimating an LX850 telescope, you will need to test your collimation. To test the collimation, center a bright star that is overhead, with a medium/high power eyepiece such as a Meade 12mm eyepiece. Allow the telescope optics to adjust to the temperature of your observation site before proceeding; temperature differences between the optics and the outside air can cause distortion in the images. Autostar II offers an option in the Utilities menus that displays the "Ambient Temperature" (the temperature of the air around mount). When the star is centered, de-focus the image. You will notice that the out of focus star image looks like a (1) (2) (3) Figure 34 : Collimation ring of light surrounding a dark central spot; the dark central spot is in fact the shadow of the secondary mirror. You may notice multiple rings; these are called diffraction rings. Focus until the diffraction rings fill about 10% of the eyepiece field-diameter. If the dark central spot is offset in (i.e., not concentric with) the diffraction rings, your telescope's optical system is misaligned and requires collimation. Collimation of the optical system: Meade ACF Models ONLY a. The only adjustments possible, or necessary, on the Advanced Coma-Free LX850 telescope models are from the three screws (Page 8, Fig. 2, #35) located at the edge of the inner surface of the secondary mirror housing. Caution: Do not force the three collimation screws past their normal travel and do not loosen them more than two full turns in a counterclockwise direction or the secondary mirror may come loose from its support. You will find that the adjustments are very sensitive, usually requiring only one-half turn or less to produce the desired result. b. While looking at the defocused star image, notice which direction the darker shadow is offset in the ring of light or notice which part of the ring is the thinnest (Fig. 34, #1). Place your index finger in front of the telescope so that it touches one of the collimation set screws. You will see the shadow of your finger in the ring of light. Move your finger around the edge of the black secondary mirror support until you see the shadow of the finger crossing the thinnest part of the ring of light. At this point, look at the front of the telescope where your finger is aiming. It will either be pointing directly at a set screw, or it will be between two set screws aiming at the set screw on the far side of the black secondary mirror support. This is the set screw that you will adjust. c. Using the AutoStar II's Arrow keys at the slowest slew speed, move the defocused image to the edge of the eyepiece field of view (Page 23, Fig. 34, #2), in the same direction as the darker shadow is offset in the ring of light. d. Turn the set screw that you found with the pointing exercise while looking in the eyepiece. You will notice that the star image will move across the field. If while turning the set screw, the defocused star image moves out of the eyepiece field, then you must use the slew keys on the AutoStar to return the star to the center of the field of view. If the screw you are turning becomes very loose, tighten the other two screws by even amounts. If the screw you are turning gets too tight, un-thread the other two by even amounts. f. When you bring the image to center (Page 23, Fig. 34, #3), carefully examine the evenness of the ring of light (concentricity). If you find that the dark center is still off in the same direction, continue to make the adjustment in the original turning direction. If it is now off in the opposite direction, you have turned 24