From: "Pete Newman" Subject: Altitude offset jump in 2.5m obslog 20020114 (MJD 52289) Date: Tue, 15 Jan 2002 09:47:08 -0700 The observers recorded some important clues about our pointing woes last night. Snippets: ======================== 3 825: ------- Guide stars on slew 8 572: ------- Guide stars on slew 3 825 ( second mounting ): --------------------------- no guide stars or fk5. Spiral pattern located it about a dozen arcseconds away. 5 525: ------- Guide stars seen once the altitude offset for 825 was removed. [UT] getclock Axis position and calibration offset Scale Time Ct Plate time Az El Rot Factor ------------------------------------------------------------------------------ 01:38 1 802 1011058704 22.39 .0053 55.09 .0008 198.65 .0001 1.000130 05:22 3 825 1011072162 100.75 .0036 62.41 .0006 -97.70 -.0068 1.000130 07:11 8 572 1011078694 54.10 .0037 47.58 .0004 223.00 -.0068 1.000130 09:52 3 825 1011088347 258.73 .0038 61.40 .0040 97.90 -.0107 1.000130 11:06 5 525 1011092799 39.46 .0033 52.79 .0015 213.59 -.0195 1.000130 ^^^^^ ^^^^^ Constant Jumps! ======================== The second mounting of 825 was off by the dreaded dozen arcseconds (this time in ALT!). There is no altitude fiducial-correction-too-large error in the murmur log for last night (see below). The calib offset in az is not small, but is fairly constant. Why did the alt calib offset jump, and then actually not return to the same zero-point again afterwards? Did cartridges 3 then 5 not mount accurately? Do the kinematic mounts on the telescope shift? What else could it be? For the record, the only too-large errors last night were on azimuth (lines trimmed, times in MST): [When slewing after the first plate 825 exposures, probably to the next field.] Jan 14 23:50:04 ... correction for azimuth 75688 is too large [This apparently corrected itself just after the next plate at 02:29 MST.] [Then when heading for telescope closure at the end of the night] Jan 15 05:42:32 ... correction for azimuth -604971 is too large Jan 15 05:42:46 ... correction for azimuth -200527 is too large Jan 15 05:47:17 ... correction for azimuth -200527 is too large Jan 15 05:51:56 ... correction for azimuth -200527 is too large Jan 15 05:52:28 ... correction for azimuth -200527 is too large By the way, thanks, Dan for recording the axis positions as well as the offsets - we really do need that extension in iop/logTool. I will be very happy when everything in the logs is back in one (any!) time system. --Pete