imlintran

raa · Joined: 13 Feb 2006 Posts: 3

Hi,

I am new to IRAF. I have to deproject a disc galaxy. From literature it seems that the task "imlintran" is capable of doing it. Now the help file gives that the transformation is:

xt = xt * cos (xrotation) - yt * sin (yrotation)
yt = xt * sin (yrotation) + yt * cos (yrotation)

where xrotation, yrotation should be in degrees. The problem I am facing is with regard to cos(yrotation). Is it correct? should it be cos(xrotation) as the usual rotation matrix?

Raa

fitz · Posted: Thu Feb 16, 2006 4:17 am Post subject:

The help page is correct, at least in the sense that the code is implemented that way. I can't explain the difference off the top of my head, but keep in mind there are separate angles specified for the X and Y rotation where the standard rotation matrix assumes orthogonal axes and only one rotation angle. Perhaps you can dig up the derivation that arrives at the cos(yrot) term, I couldn't find it in the online docs.

-Mike