Sunspot Band6 Feathering for CASA 4.7

Overview

This portion of the Sunspot Band6 CASA Guide for CASA 4.7 covers the combine process between the synthesized solar image and the full-sun image obtained with TP array. It begins where the calibration of the visibility data and single-dish data, image synthesis, and creating of the full-sun map are completed. If you do not complete them, at first,

1) Download the file of the un-calibrated data package ‘Sunspot_Band6_UncalibratedData.tgz’, do the calibration of the data, and create the images from the interferometric data and single-dish data, along with the ‘Sunspot_Band6_*_for_CASA_4.7’ tutorials.

or

2) Download the file of the calibrated data package ‘Sunspot_Band6_CalibratedData.tgz’, and synthesize the image from interferometric data along the ‘Sunspot_Band6_Imaging_for_CASA_4.7’ tutorial.

In case 1), we assume that you are working on the working directory ‘Sunspot_Band6_UncalibratedData’. On the other hand, when you started the tutorial from the calibrated package (case 2), we assume that the working directory is ‘Sunspot_Band6_CalibratedData.’

From next, we will show all commands for combining the images. If you do not want to cut-&-past the commands, you can use the script as described in #Alternative way of Combining Images.

Obtaining the RA/Dec coordinate of the sun center at the reference time

Before starting the combination process on CASA, we need to know the RA/Dec coordinate of the sun center at the reference time that is used for the image synthesis, because the observing time of the TP-array is not the same as the reference time exactly. The Sun was moving on the RA/Dec coordinate frame during the gap between the times. To combine the synthesized image with the full-sun image obtained from the TP array, we need to shift the coordinate of the full-sun image based on the coordinate of the sun center at the reference time. Hence, we obtain the solar coordinate from the JPL’s HORIZONS system[[1]].

The reference time in this tutorial is 19:49:00UT, December 18 2015. At the time, the RA/Dec coordinate of the sun center estimated by JPL’s HORIZONS system is RA: 266.01898 degree, Dec: -23.38648 degrees.