2 Observations

 

 

Table 1: All observing runs, with array configuration, RFI type (Sect. 3.1), maximum baseline length (ranging with observing direction and time of day) and number of useful fields in the run

Date	Array	RFI TYPES	UVMAX	N
200293	AB	G	75-110	73
080693	BC	W, G, S206	30-37	71
090693	C	W, G, S206	16-18	70
100693	C	G	17-18	70
310893	C	G, S226	7-12	73
020993	CD	W, G	7-12	46
090993	CD	W, G, S226	7-12	72
210594	AB	W, G, S210	100-120	38
260594	AB	W, G	70-120	69
280594	AB	W, G, S 200204	75-120	73
310594	AB	W, G, S208	80-120	62
010694	AB	W, G	75-105	59
030694	AB	G	55	13
160994	BC	W, G, S 208225	25-37	62
210994	BC	G, W	25-37	70
220994	BC	G, W	24-37	74
210695	A	W, G	180-200	51

The observations were taken with the VLA between 1993 February and 1995 June, in configurations ranging from A to CD (Table 1). The area of this northern part of the survey consisted of $13 \times 81=1053$ pointing centres. Due to system failures and compact antenna configurations in combination with radio-frequency interference (RFI), useful data were obtained for only 965 (Fig. 1).

The full width at half maximum (FWHM) of the primary beam (PB) of the VLA antennae at 1612.231 MHz is 27$^\prime$. The data were taken in circular RR polarization, using a total bandwidth of 3.3 MHz (614kms^-1) and 255 spectral channels (separation 2.27kms^-1). Doppler tracking was used during the observations, transforming the velocities to the frame of the local standard of rest (LSR), so the spectral band was centred at 0kms^-1 for each pointing.

We used mostly 0137+331, or if necessary 1331+305, as the primary calibrator and 1822-096, 1911-201, 1751-253 and 1751+096 as secondary calibrators. On each field, an integration time of $10 \times 30$ s was scheduled, with in general 300 baselines available for observing.