Down Time

In Table 1 the down time statistics for the period 2002-10-01 to 2003-03-31 are reported. The main change in the reporting of down-time with respect to previous periods is that we have changed the options for reporting down-time from `$<$1 hr', `2hr', ..., `10 hr', `All night'; to: `5 min', `10 min', `15 min', `30 min', `45 min', `1 hr', `1.5 hr', `2hr', ..., `10 hr', `All night'. The implication of this is that we can give a fairly accurate indication of the total time lost, not just an upper limit.

In a total of 50 End-Of-Night reports faults were reported, with an average time lost of 32 min per fault. Of these, 29 reported no time lost, 19 reported $<$ 2 hr lost, and 2 reported 2 or more hrs lost.

Table 1: Technical down time statistic 2002-10-01 to 2003-03-31

Night included	Time lost	Nights	Percentage$^a$	Last period
All nights	1590 min	182	1.5%	$<$ 2.8%
Scheduled observing nights$^b$	1520 min	121	2.1%	$<$ 2.6%
Technical nights	70 min	28	0.4%	$<$ 5.1%
Visitor instruments	0 min	33	0.0%	0.0%
$^a$ Assuming an average of 10 hr per night
$^b$ Excluding technical nights and visitor instruments

This compares to a down time of $<$ 2.8% over all nights ($<$ 2.6% on scheduled observing nights) in the period 2002-03-12 to 2002-09-31 (which is slightly different from the period in the last STC report to be instep with the start and end of the semesters). In that period in 53 End-Of-Night reports faults were reported, of which 29 reported no time lost, 16 reported $<$ 1 hr lost, and 7 reported 2 or more hrs lost. The main difference between the current reporting period and the last reporting period is the number of faults resulting in large (2 or more hrs) down-time.

Below are listed those faults for which 2 or more hours were lost. Also repetitive errors which lose little time but occur frequently are included here.

• 2002-11-08: Telescope motor brushes holder: All night

  The holder of the brushes in the motor got burned as a result of short-circuiting due to aging of the brushes. Spares have been ordered.

• 2003-03-18: NOTCam filter wheel no. 2: 7 hr

  The filter wheel no. 2 in NOTCam could not be moved normally. In the end it was possible to get the filter wheel to a fixed position, and the observed selected to observe with one filter per night. After opening the instrument it was found that the bearing of the wheel gear was stuck. It was replaced with a spare.

  The next time that NOTCam will be opened the bearing of the other filter wheels will be checked. It was noted that filter wheel no. 2 is the one that is most often used (it contains the broadband filters).

• 2002-03: Pointing: 1 hr

  In various reports (with little time lost in each separate report) it was noted that the telescope pointing was of significantly. A new pointing model was made and installed (see below).