Chuck, Thank you! That was amazing. The tracking error went down to ziltch - 21" in RA over 600 seconds. A revised tracking graph - which has a competely different scale from the last one - was prepared. Ealing drive tracking error test http://gallery.utahastronomy.com/main.php?g2_itemId=11531 For lurkers that means when the Ealing drive is calibrated and you put Saturn or M13 in the scope - it will stay in the e.p. view for a good half-hour. And to create a new Chuck Hards myth story - The answer on Cloudy Nights was: "Drop Roland and Marj [former Astrophysics owners?] an email. They may still remember..." Chuck's answer was "Oh yeah, I have two of those 30 year old drive controllers in the garage - with autoguiders." A modest start after calibrating the drive - Alberio on the Ealing http://gallery.utahastronomy.com/main.php?g2_itemId=11529 ======================= Use notes on the Ealing for lurkers With drive calibration, the Skywizard still registers an index error of about 0.3 degs in RA only for a 9 deg slew on two tests (Vega to M57 and Vega to M13). That means at best the Skywizard will put a target somewhere in the Mak view, but it cannot be used for actually getting the target into a short-focal length (32-25mm) observing eyepiece. CHEAT SHEET FOR CALIBRATING THE EALING'S ASTROPHYSICS MODEL 8002 DRIVE CONTROLLER The controller uses a quartz crystal to generate a reference signal. Knobs and lights on the front of the controller, left to right, are: Calibration Light Power Mode - Sidereal, Solar, Lunar, Calibrate Calibration Knob - This is non-functioning. Set it to the middle and forget it Auto-Manual RA - Always set to manual Auto-Manual Dec - Always set to manual Plug-input for the slow motion control and also off to the side - Separate slow motion control with rate dial knob. Procedure: 1) On start-up, set the Mode to "Calibrate". 2) The Calibration Light will slowly flicker over 0.5 to 2 seconds. 3) Using the dial knob on slow motion control, turn the knob until the rate of flicker in the calibration light is minimized. Typically, it will flicker over 2-5 seconds. On start-up the crystal is cold and you will not be able to absolutely calibrate the drive rate. You can only do a rough calibration. 4) After using the scope for 30-45 minutes, the reference-signal crystal will reach operating temperature. 5) Repeat steps 1-3. This time you will be able to adjust the calibration light so it will stop flickering and hold with a _steady glow_. 6) Avoid turning the dial rate knob when using the slow motion controller. I bumped it while in the middle of imaging, accidentially changed the setting, and M13 zipped right off the camera chip. Once calibrated, the drift rate for commonly observed objects will effectively disappear and the sub-arcsec drift error rate is in a zone sufficient for astrophotography. Once calibrated, the "lunar" mode also does a fair job of lunar target tracking. In lunar mode, the Ealing will track well within any limitations needed for imaging and stacking lunar images within Registax. Without drive controller calibration, DSO will drift out of an Ealing 32mm-25mm observing eyepiece in two to three minutes. =============== The above probably should be added to the Ealing training cirriculum. Peace - Kurt