Meade LX850-ACF 10 inch User Manual - Page 26

StarALuotcokStAanrd#4M9o7unHtAFNleDxBuOreX StarLock Automatic Rate Calibration (ARC) Obtaining best performance from StarLocked telescopes requires that the guiding aggressiveness be optimally set for current viewing/imaging conditions. This is an essential procedure to obtain peak tracking accuracy Please refer to Appendix C, page 53 for details. Periodic Error Correction Training the mount using AutoStar's built-in Periodic Error Correction is necessary to achieve peak performance of the LX850 Telescope System. This is especially true when you are taking long exposure photography. Periodic Error Correction should be done after you have fully assembled your mount, balanced with all the auxiliary equipment you plan on using and you have successfully aligned the telescope. It is also important that this performed under reasonably dark skies with good seeing conditions. If atmospheric conditions are poor you will not obtain accurate error correction. See page 43 for directions on how to perform the Periodic Error Correction routine. StarLock And Mount Flexure The StarLock is normally attached to the saddle plate of your mount. When enabled, it waits a few seconds after the completion of a slew, and then automatically finds a guide star and begins auto-guiding your telescope. This assures that your mount will precisely compensate for the movement of stars across the sky. Provided your telescope is securely attached to the mount, it too will track precisely with the movement of stars across the sky. If the position of your OTA, camera, diagonal or eyepiece changes over time, you will see a small drift in the position of objects. This problem is known as differential flexure. Meade's LX850 OTAs have been engineered to limit flexure sufficiently to make images up to 10 minutes or longer in duration without any noticeable movement of objects. Often, depending upon where you are pointed you can go much longer. If you are experiencing drift due to flexure, you need to track down what is loose and tighten it up. Things to check include: StarLock Mounting The StarLock's Dovetail should be centered in the dovetail bracket with its base flush against the bottom of the saddle plate. Be sure the dovetail bracket is tight and no movement of the StarLock is occurring. Note that 10", 12" and 14" LX850 ACF optical tubes include their own StarLock mounting bracket located at the top of the OTA, towards the rear cell. This second bracket is the preferred mount location for StarLock as it minimizes flexure in these long focal length OTAs, OTA Mounting Likewise, the OTA's dovetail plate should be flush against the Saddle Plate and the Dovetail bracket should be tight. Additionally, you should check that the cap head screws securing the dovetail to the telescope are tight. This includes the plate interface brackets that connect the OTA to dovetail plate. Focusers If you are using a refractor, be sure that the focus lock is tightened once you have achieved focus. Crayfordstyle focusers are secured via pressure on a rolling pin. Too much force and the scope will not focus, to little and the focuser tube can shift as you scope tracks around the sky, especially with a heavy camera hanging off the end. Cameras Be sure your camera is securely attached to the telescope. Inserting the camera in a draw tube and tightening a single captive screw is a recipe for image shift. Draw tubes should have at least two and preferably three captive screws so the camera cannot shift when the scope moves about the sky. Reflecting Telescope Mirrors If you are using a telescope with primary mirror atop the LX850 that does not have Meade's "Zero Shift" technology, you must lock your mirror, otherwise as the scope moves about the sky, the different stresses will cause the mirror to flop making long exposures impossible. Heavy OTAs If you are using a very heavy OTA, near the 90 pound limit of the LX850's capacity, it may prove difficult to prevent differential flexure. If this is the case, you can improve performance by attaching the StarLock to the top of your OTA. While this makes it inconvenient to exchange OTAs, it may resolve many flexure problems. The orientation of the StarLock should not change. It should still be square to the Saddle Plate. Attaching the StarLock to your OTA will mean that it will not only compensate for star movement relative to the mount, but star movement relative to the OTA itself. 26