In order to coalign two solar images from two different observational
instruments, we need to know the values listed below
between the two images:
Please note that the differences of roll angles and pointings may vary with time.
The XRT team distributes the XRT Coalignment Database through SSWDB. The database and its IDL interface programs provide all XRT data users with the necessary information for coalignment. XRT data users can achieve coaligned results by using the database and its IDL interface programs.
The database is the results of our calibration works and being updated
automatically weekly basis.
You can find the details of the calibration in:
Since the standard data preparation software "xrt_prep.pro" uses the database in one of its correction steps, your prep'ed "index and data" should already have the corrected information for coalignment. Please be aware that the correction process for coalignment does not modify the data array, but changes the meta data stored in "index". In order to achieve the coalignment, you need some extra steps after the meta data correction. See the below section "How to achieve coalignment images".
Below I put three sample programs to show how to achieve coaligned images.
(1) Quickly see the coalignment (interactively): ky_sample4.pro
Just run the program, like:
IDL> .r ky_sample4(2) Quickly see the coalignment (non-interactively): ky_sample5.pro
IDL> .r ky_sample5(3) Create coaligned array: ky_sample6.pro
IDL> .r ky_sample6You will get a coaligned array "data".