Date: Fri, 17 Sep 1999 06:04:14 -0600 From: Dan Long Subject: 2.5m obslog 990916 ( MJD 51438 ) THURSDAY SEPTEMBER 16, 1999 APACHE POINT OBSERVATORY SDSS 2.5m OBSERVING LOG Observering team: Dan Long (APO) Stephanie Snedden (APO) Scot Kleinman (APO) Scott Burles (UC) Connie Rockosi (UC) Robert Lupton (PU) Tonight's plan was to obtain imager data scanning "backwards" on the equator to test whether the focal plane tilt is due to the imager or the optics being tilted. This was to be followed by as much spectrographic data the remaining night allowed. The imaging goal was achieved, but the abbreviated open time due to weather prevented getting any useful spectro data. Opening was delayed until about 23:00 due to high humidity. Setup was a bit more difficult than it should have been. Inexplicably, the command TRACK 0,57.22 MOUNT /ROTTY=MOUNT /ROTA=90 followed by OFFSET ROTATOR -.152 Resulted in a rotator position of -.152 deg mount rather than the expected 89.848 deg mount. Reissuing the rotate command ( ROT 90 MOUNT ), followed by ( OFFSET ROTATOR -.152 ) worked. I was also a bit puzzled by the response of the track command to get the telescope tracking twice sidereal. TRACK RA,DEC FK5 /ROTTY=OBJ /ROTA=0 /SCANVEL=(-.00417807,0.) This command should have worked, but the first time I tried it the rotator was 180 deg off. Later "simulated" slews with the motors off showed that the above track command would send the axes where I had wanted in the first place. Perhaps I made a typo in the earlier slew. Sadly the commands are not saved in the tcc logs, only the responses, so I'll never know for sure. It would be nice if the TCC echoed each command sent to it, making it much easier to retrace one's steps when looking back at the logs. Cursory inspection of the plots from the focus loop seemed to indicate that the focus positions for the astrometrics were more separated in the backward scan than the forward scan, which with the shim in place would indicate that the optics rather than the camera are the source of the focal plane tilt. Jim will have more definitive answers once the focus sweep data are examined. At about 01:40 we finished with the imager work and proceeded to switch to spectroscopy. Everything went smoothly during the instrument change. We got back on the sky in just under an hour. The FK5 star showed up in the fiber on the first try, and focusing didn't take long. Unfortunately the sky was uncooperative and within half an hour it clouded over and we had to close at 03:15. We did not reopen. MIRROR NUMBERS Primary: setmir: 0 -7.8 7.8 427 427 galil: 5100, -2700, 200, -6050, 7300, 7000 linear gauges 1 = 1.9310 2 = 0.5585 3 = 0.5570 5 = 1.9075 6 = 0.4070 4 = 1.3150 7 = -5.7870 8 = 0.8050 TPM data was logged for most of the night using the "start tpm51438.dat" command. Robert Lupton has added some code to iop to archive the tpm data on the night's tapes. It will look for a file with the current mjd in the /mcptpm directory on host. The file name should be of the form tpm{mjd}.dat to insure that iop will find it. Nitrogen notes: Both spectrographs were filled at 20:00 and again at about 05:30. The 180 L dewar for the imager was changed at about 05:30. Note: The outer sleeve for the quick disconnect for the spectro dewars has come off. This means that nothing but friction holds the nozzle onto the dewar. Once cold it stays put, but until it gets cold you have to hold it in place. WEATHER Weather tonight was mostly clear at sunset. The humidity rose above the limit shortly before the sun went down. Condensing humidity remained until around 23:00. At about 03:00 it clouded over and it remained cloudy the rest of the night. Temperatures were in the lower 50s most of the night. Winds were out of the SE most of the night. Dan