Date: Sun, 27 Dec 1998 07:14:13 -0700 (MST) From: Russet McMillan Subject: 3.5m Night Log 981226 Apache Point Observatory, Sunspot, NM Saturday, December 26th, 1998 3.5-meter Night Observing Log Actual ----------------------------------------------------------------------- ASTRONOMER OBSERVER(S) INSTRUMENT DATE START FINISH ----------------------------------------------------------------------- E.Turner C.Hastings SPIcam 12/26 18:32 19:23 D.York G.Richards DIS 12/26-27 19:23 00:10 S.Kent G.Richards DIS 12/27 00:10 05:36 ----------------------------------------------------------------------- INST SCHEDULED WEATH EQUIP OBS DAY NOTUSED I/RS/DN START FINISH D B D B D B USE D B ----------------------------------------------------------------------- PU01/S 18:32 19:23 - 0.8 - 0 - 0 0 - 0 UC01/R 19:23 00:10 - 2.3 - 0 - 2.5 0 - 0 UC10/R 00:10 05:36 0 0 0 0 4.7 0.8 0 0 0 -------------- Activity Log -------------- 1st Half Observing Specialist: Camron Hastings I opened at 17:10 MST with cloudy skies. The high cirrus thinned a bit so I decided to go ahead with the lens monitoring. Not a very good night for lens observations. Early in the afternoon Gordon Richards came on and checked the DIS wavelength centers. We did this without mounting DIS, just pointed it in the direction of the mirror covers. The blue grating needed to be adjusted by 1 step. It seems that it is always the blue grating that needs re-adjustment. I closed again at 20:40 due to increasing clouds and no data of worth. Actually, Gordon said the scattered moonlight produced more solar lines than anything else! 2nd Half Observing Specialist: Russet McMillan The telescope was re-opened at 22:55 as the clouds were somewhat thinner. Second half was partly cloudy and once again windy with poor seeing. We were using DIS with horizon rotation, and once again I saw frequent occurrences of the guider error "centroid failed; center isn't highest pixel." I observed some of these pretty carefully, and this is what I think happens. The star slowly moves across the chip as the rotator follows the parallactic angle. In the course of its motion, the star passes near a hot pixel on the guider chip. That causes the first appearance of the error. The star slowly passes the hot pixel until eventually it's in a clean area of the chip -- meanwhile, the guiding software is *guessing* where the star should be, but it's not right on. By the time the star is far enough away from the hot pixel to resume guiding, it has also moved outside of some error box for centroiding. Karen suggested creating a new bad-pixel map for the guider. If this works as expected (i.e., the software ignores the bad pixel, but can still tolerate having a star nearby), it should be a good long-term solution. A more immediate solution would be to adjust the size of the centroiding error box -- is there a way to do that? The list of gcam commands merely says that the center must be specified to "within an arcsecond or so." OBSERVER COMMENTS Started the night with some nice solar spectra (lots o' moon and clouds). After we opened again, things went pretty well. Many thanks to Camron and Russet. FOCUS LOG December 26th 1998 Best Telescope Temp Wind Seeing Time Instrmnt Focus Az El Air/Truss Dir MPH filter FWHM" ---------------------------------------------------------------------- 18:20 SPIcam +050(6377) 223 53 3.8/4.2 299 17 g' 1.52" 18:30 Guider 56505(6377) 226 53 3.2/3.8 311 12 none 1.24" WEATHER LOG December 26th 1998 Wind Time Temp-F Dewp-F MPH Direction Dust Sky Precip ------------------------------------------------------------------ 16:01 38 9 12 302 (WNW) cirrus none 17:01 37 8 16 320 (NW) cirrus none 18:01 38 10 14 303 (WNW) cirrus none 19:01 38 12 15 334 (NNW) cirrus none 20:01 38 14 19 307 (NW) cirrus none 21:01 39 15 10 299 (WNW) cirrus none 22:01 39 16 15 310 (NW) cirrus none 23:01 37 15 12 342 (NNW) cirrus none 00:01 39 15 22 332 (NNW) cirrus none 01:01 40 18 22 318 (NW) cirrus none 02:01 39 17 19 323 (NW) cirrus none 03:01 39 18 11 300 (WNW) cirrus none 04:01 38 17 12 40 (NE) cirrus none 05:01 38 16 12 8 (N) cirrus none 06:01 37 17 11 344 (NNW) cirrus none note: the wind was coming from the azimuth listed. The convention used is north=0 degrees, east=90 degrees. The dust count is for the particles > 1 micron per 0.1 cu.ft. TELESCOPE STATUS Primary, secondary, and tertiary mirrors in place and collimated. Primary support system operational. Mirror ventilation system in place. Telescope drives operational. Current Remark version: 2.42a Current guide software version: GIm Ctrl v3.0b 15.out - NCH, RM