wide-field corrections.

We obtain output images at every snapshot (112s) and coarse band channel (1.28MHz) in the HEALpix frame [@2005ApJ...622..759G]. For reducing the thermal noise contamination, 90 observations are integrated into a main image at every $\sim$ 8MHz, namely a main image includes 540 snapshots. Left panel of Fig. \[fig:image\] is the image centered at 171MHz using natural weighting. This image is almost consistent with the Figure. 8 in [@2016ApJ...833..102B] except the size and resolution. There is apparent diffuse emission and un-subtracted point sources. Note that the lack of visibility at $(u,v) = (0,0)$ (no auto-correlations) causes the negative values, whereby a constant sky temperature cannot be reconstructed.

In addition to the images, the calibrated visibility data are an output of the RTS. In this work, we take the average of the visibilities in the uv plane with $\Delta u = 1$ at every coarse band channel. These gridded visibilities are used to calculate the angular power spectrum.

![image](./Fig_paper/MWA_image.eps){width="7cm"} ![image](./Fig_paper/MAP_CMB.eps){width="7.5cm"}

Methods {#S:method}
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In this section, we describe the method to calculate the angular power spectrum (APS), cross power spectrum (CPS) and the error of the CPS.

Angular Power Spectrum
----------------------

The APS is defined as ensemble average of spherical 