650 MHz image of the gain calibrator field (J1851+005) of our observations. Circled in red at the center is the phase calibrator (J1851+005; Galactic coordinates l = 33.5°, b = 0.2°). The large and extended structure to its southeast is the supernova remnant (SNR) G33.6+0.1. The beam size is about 10 arcsec. The intensity scale is saturated to clearly bring out the weak extended structures.