| Home > Astronomy > William Herschel Telescope > Quality Control > WHT tracking |
| Home > Astronomy > William Herschel Telescope > Quality Control > WHT tracking |
WHT trackingAway from the zenith, the WHT should be able to track open-loop (i.e. without autoguiding) for 10 minutes with errors < 1 arcsec in each coordinate. Below are the results of occasional tests on-sky (usually through cloud), monitoring the movement of a star on the TV or on the autoguider: Date AZ EL Time DAZ DEL yyyy mm dd deg deg mins " " 1998 01 15 hi 15 ~ 3 ~ 3 1991 01 23 ~60 30 < 1 < 1 1991 01 23 ~60 30 < 1 < 1 1999 09 24 180 80 35 2.4 3.0 " 200 60 20 <0.3 <0.3 " 150 50 20 0.0 2.9 " 180 50 20 0.2 1.4 " 170 40 25 0.8 1.6 " 170 30 15 0.4 0.9 2005 09 32 66 30 0.0 1.4 2005 11 20 21 58 15 1.3 2.3 2006 05 10 66 15 0.0 -1.9 2006 05 10 29 15 0.1 -0.8 2006 05 12 197 68 15 0.4 1.4 2006 05 12 191 58 15 1.4 1.5DAZ, DEL are the arcsec shifts required in azimuth and elevation to restore the position of the star after the indicated elapsed time. The signs of DAZ and DEL are not always recorded. The drifts are usually steady, monotonic.
Problems during 1999
During the 5/99 PF run, nearly all images were elongated in elevation, with ellipticities 0.05 - 0.15. Poor tracking might have been responsible, but the atmosperic-dispersion corrector is also suspected. Significant errors in elevation tracking have not been seen since. During the 6/99 ELECTRA run, fast glitches ~ 0.5 arcsec (there and back in << 1 sec) were noticed, sometimes almost continuous, probably in azimuth. The telescope control system includes corrections for each derotator, documented on the WHT derotators page. Chris Benn (crb@ing.iac.es) 2006 May 15 (original 1998) |
| Top | Back |
|
