| Step | How to | Tricks with DS9 | Example/Filename |
|---|---|---|---|
| Select a reference image | Your reference image should be the smallest of your images if they are different sizes | image1.fits
| |
| Select stars in reference image | Use display to display an image in DS9 (you may have to set stdimag=imt2048, then use imexamine with the a,r, or x
keys to find star coordinates in pixel position |
Use DS9 regions to select a list of stars and use the region file | starcoords.txt |
Find the relative shifts between images if the shifts are greater than the bigbox parameter of imalign |
Use disp and imexam to find the coordinates of the same star in each image, and calculate the relative shifts
between those stars. The shifts should be of the form ( refx - imagex ,refy - imagey ) |
Copy and paste DS9 regions between the files. It is helpful to have one ruler region included to make the measurement easier. | shiftlist.txt |
| Make a list of input and output files | Edit two files and put in the list of input/output files. Make sure your reference image is the first one. | Use UNIX tricks | inlist.txt, outlist.txt |
imalign @inlist.txt image1.fits starcoords.txt @outlist.txt shifts=shiftlist.txt | |||
Remember that inlist.txt, outlist.txt, and shiftlist.txt have to have the same number of items in them! | |||
| If you get segmentation violations or similar errors, make sure that the coordinates and shifts are separated by SPACES, not COMMAS. | |||