Excluding a rectangular region from an image in FITS I am a complete beginner in astronomy. While learning DS9, I came up with the following question.

Say I want to exclude a boxed region from an image FITS. The corresponding parameters according to Chandra is


Box = (xcenter,ycenter,width,height)
Box = (xcenter,ycenter,width,height,angle)


Although the name is self-explanatory yet I am confused about their respective units. What unit is used to label these parameters?
Usually pixel coordinates.
What I would do is to let DS9 make a region file, as your documentation site says it supports them.

To do so:


Open file in ds9
From region->shape select the kind of region you want.
Click on edit->region
Draw the shapes you want (just click on the img)
Click region->save. In the coordinates box choose physical pixel coordinates.


Probably that should work... Good luck!