Introduction

In the current incarnation of the Standard Field observations, a field at $\alpha = 3^{\rm h} \, 10^{\rm m}, \ \delta = +80^\circ$ (B1950) is observed for $\sim$ 6 hours at X-band and L-band once during each VLA configuration. This has been the case since the A configuration in 1993. Prior to that, the observations had a much broader scope, including observations of that same field at many bands, and pointing tests, among other items. However, it was decided that most of the things being done with the Standard Field observations were better done under different auspices, hence the change. In November 1995, the scope of these observations was again changed, with the Standard Field only observed for a short period ($\sim$ 1 hour) once a year, probably in the D configuration. This memo is intended to summarize the Standard Field observations during the period from 1993 to 1995. Previous to the D configuration of 1992, the Standard Field observations were taken care of by Pat Crane. From that point to the A configuration of 1994, they were taken care of by K. Dwarakanath ("Dwaraka"). From that point until the B configuration of 1995, I took care of them. Currently, Greg Taylor has agreed to take over the reduced Standard Field observations.
When these observations were initiated, this field was a ``blank'' field to the VLA, i.e., one with no detectable sources. With the increase in sensitivity of the VLA, this is no longer the case. Figures 1 and 2 show images of the field at both frequencies, taken from the D configuration observation in 1995. These figures show that there are many detectable sources at L-band, which extend out into the secondary lobe of the primary beam. There are also several detectable sources at X-band. These sources (at both frequencies) are all greater than 5 times the rms noise in the image.

Figure: Image of the Standard Field at L-band.

Figure: Image of the Standard Field at X-band.

The last X-band measurements were done in continuum mode with the IFs centered at 8435.1 and 8485.1 MHz (changed from the old values of 8414.9 and 8464.9 MHz as of the B configuration observation in 1995, as per Greg Taylor's email of 10/3/95 regarding changing the X-band default frequencies). The last several L-band measurements were done in continuum mode, with one of the IF's centered at 1364.9 MHz, and the other at either 1435.1 or 1485.1 MHz (see discussion later). Prior to the D configuration observation in 1995, the L-band measurements had been done in spectral line mode, bandwidth code 0, yielding 7 Hanning smoothed channels of 6.25 MHz each. The older observations were done in two separate IFs (A and B), with bands centered on 1464.9 and 1385.1 MHz, respectively. The modifications that were made to the L-band measurements over time will be discussed later. Calibration was done in a mostly standard fashion, with the absolute scale being set by an observation of 3C286 or 3C48, and complex gains calibrated by observation of the calibrator 0212+735 (B1950). For the spectral line L-band observations, the absolute flux calibrator was also used to calibrate the bandpass. After editing, the Standard Field (0310+80) was split out into a single source file.