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Polar Axis Alignment

(2 July 2006)   The telescope is mounted on a fixed-angle wedge so that when the pier head is leveled, very little additional adjustment is needed. I used drift alignment to judge adjustments to the leveling screws and rotation of the wedge. This gave pretty good results at the end of last Summer, but was tedious. The adjusting screws are not easy to turn.   This Summer I fired up PoleAlignMax and determined that the polar axis of my telescope was about 8 minutes of arc below and 40 seconds of arc to the west of the North Celestial Pole. Based on those results, I made fine adjustments to try to get within a minute of arc or so in both coordinates. It was easy to raise the polar axis of my mount by 8 minutes of arc, although it took six iterations to get there.   Below is a screen image of the last iteration, showing the log file and the polar diagram of the displacement, along with a dump of the log file.   At first, I had trouble with PoleAlignMax because often the image could not be plate-solved. PAM won't work to completion if any one of the three images can't be solved. When I was able to get all images to plate solve, PAM worked without a failure. As I mentioned elsewhere, I got plate solving to work because I shortened the telescope focal length by adjusting the spacing between the focal reducer and the CCD image plane, which made the camera faster (more stars per unit exposure time) and covered a larger field of view (more stars in the field of view).

Screen Dump of PoleAlignMax

PoleAlignMax log file 22:40:31 Start Alignment Run 22:40:31 Telescope at RA = 15.50194 Dec = 0.00000 22:40:31 ***** Exposing Image 1 ***** 22:41:13 Start Solving Plate 1 22:41:13 Step 1: Found 22 objects in image. 22:41:13 Plate Solve Attempt at RA = 15.50194 Dec = 0.00000 22:41:13 Step 2: Look up catalog stars for area... 22:41:14 Step 2: Found 106 catalog stars in area. 22:41:14 Step 3: Solve the plate... 22:41:14 Solved using 15 stars, average residual is 0.40 arcsec, order =1 22:41:14 Solution took 1.5 seconds 22:41:14 RA = 15h 29m 45.341s 15.49592814 22:41:14 Dec = 00° 00' 46.33" 0.012870 22:41:14 Roll = -0.208 HScale = -1.096 VScale = -1.097 Binning = 1 22:41:14 RA Error = -0.006016 22:41:14 Dec Error = 0.012870 22:41:15 Plate 1 Solved 22:41:15 Plate 1 RA = 15.495928 22:41:15 Plate 1 Dec = 0.012870 22:41:13 Telescope at RA = 15.33528 Dec = 0.00000 22:41:53 ***** Exposing Image 2 ***** 22:42:50 Start Solving Plate 2 22:42:51 Step 1: Found 17 objects in image. 22:42:51 Plate Solve Attempt at RA = 15.32926 Dec = 0.01287 22:42:51 Step 2: Look up catalog stars for area... 22:42:51 Step 2: Found 80 catalog stars in area. 22:42:51 Step 3: Solve the plate... 22:42:51 Solved using 9 stars, average residual is 0.24 arcsec, order =1 22:42:51 Solution took 1.0 seconds 22:42:51 RA = 15h 19m 44.616s 15.32905997 22:42:51 Dec = 00° 00' 38.97" 0.010824 22:42:51 Roll = -0.191 HScale = -1.094 VScale = -1.097 Binning = 1 22:42:51 RA Error = -0.006218 22:42:51 Dec Error = 0.010824 22:42:52 Plate 2 Solved 22:42:52 Plate 2 RA = 15.329060 22:42:52 Plate 2 Dec = 0.010824 22:42:59 Telescope at RA = 15.16861 Dec = 0.00000 22:43:04 ***** Exposing Image 3 ***** 22:43:37 Start Solving Plate 3 22:43:37 Step 1: Found 14 objects in image. 22:43:37 Plate Solve Attempt at RA = 15.16219 Dec = 0.00878 22:43:37 Step 2: Look up catalog stars for area... 22:43:38 Step 2: Found 91 catalog stars in area. 22:43:38 Step 3: Solve the plate... 22:43:38 Solved using 8 stars, average residual is 0.39 arcsec, order =1 22:43:38 Solution took 0.9 seconds 22:43:38 RA = 15h 09m 45.371s 15.16260318 22:43:38 Dec = 00° 00' 32.27" 0.008964 22:43:38 Roll = -0.284 HScale = -1.098 VScale = -1.096 Binning = 1 22:43:38 RA Error = -0.006008 22:43:38 Dec Error = 0.008964 22:43:39 Plate 3 Solved 22:43:39 Plate 3 RA = 15.162603 22:43:39 Plate 3 Dec = 0.008964 22:43:39 A = -3.77440299251188E-05 C = 0.999999756533815 Theta = 3.77440390965925E-05 22:43:39 Gamma = 6.96489296022242E-04 22:43:39 Error Amplitude = 0.0400 Degrees from Pole (Dec units) 22:43:39 Error Angle = 273.1019 Degrees CCW from Up 22:43:39 RA Offset = 0, Dec Offset = -1.55071321446969E-02 22:43:47 Telescope at RA = 15.50194 Dec = 0.00000 22:44:09 Alignment Run Complete 22:44:56 ACP Telescope Hub (ASCOM) is disconnected