How to Coalign Images from Hinode/XRT to Those from Other Instruments

Basics of image coalignment

In order to coalign two solar images from two different observational instruments, we need to know the values listed below between the two images:

If the parallax and image deformation/distortion are all corrected, we can coalign the two images with these information.

Please note that the differences of roll angles and pointings may vary with time.

The XRT Coalignment Database and the interface programs

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 "" 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".

How to achieve coaligned images

Below I put three sample programs to show how to achieve coaligned images.
(1) Quickly see the coalignment (interactively):

Just run the program, like:

    IDL> .r ky_sample4
(2) Quickly see the coalignment (non-interactively):

Modify the program to point to the proper filename and run:
    IDL> .r ky_sample5
(3) Create coaligned array:

It may be useful for further analysis.
Modify the program to point to the proper filename and run:
    IDL> .r ky_sample6
You will get a coaligned array "data".

For further information:

Please let me (Keiji Yoshimura) know, if you have any questions/comments about the coalignment.


IDL programs
DB directory