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At relatively high frequencies, highly sensitive grating sidelobes occur inthe primary beam patterns of low frequency aperture arrays (LFAA) such as theMurchison Widefield Array (MWA). This occurs when the observing wavelengthbecomes comparable to the dipole separation for LFAA tiles, which for the MWAoccurs at approximately 300 MHz. The presence of these grating sidelobes hasmade calibration and image processing for 300 MHz MWA observations difficult.This work presents a new calibration and imaging strategy which employsexisting techniques to process two example 300 MHz MWA observations.Observations are initially calibrated using a new 300 MHz sky-model which hasbeen interpolated from low frequency and high frequency all-sky surveys. Usingthis 300 MHz model in conjunction with the accurate MWA tile primary beammodel, we perform sky-model calibration for the two example observations. Afterinitial calibration a self-calibration loop is performed by all-sky imagingeach observation with WSCLEAN. Using the output all-sky image we mask the mainlobe of the image. Using this masked image we perform a sky-subtraction byestimating the masked image visibilities using WSCLEAN. We then image the mainlobe of the observations with WSCLEAN. This results in high dynamic rangeimages of the two example observation main lobes. These images have aresolution of 2.4 arcminutes, with a maximum sensitivity of 31 mJy/beam. Thecalibration and imaging strategy demonstrated in this work, opens the door toperforming science at 300 MHz with the MWA, which was previously aninaccessible domain. With this paper we release the code described below andthe cross-matched catalogue along with the code to produce a sky-model in therange 70-1400 MHz.

Imaging at 300 MHz With the MWA