Hi,

It's not always safe to get "XCEN", "YCEN" information directly from EIS fits (main) header.

Here are some suggestions (according to emails between Ignacio U., Ken D.and Viggo H. and John M.):

1. use the fits bte header (ie the data_object methods)

IDL> fname='eis_l0_20070320_030501.fits.gz'
IDL> obj=obj_new('eis_data',fname)
IDL> xpos=obj->getxpos()
IDL> ypos=obj->getypos()
IDL> xcen=total([max(xpos),min(xpos)])/2.
IDL> ycen=total([max(ypos),min(ypos)])/2.
IDL> print,xcen,ycen
      21.4457     -976.781

2. use methods provided by the hdr_object

IDL> fname='eis_l0_20070320_030501.fits.gz'
IDL> hdr=obj_new('fits_hdr',fname)
IDL> xcen=hdr->getxcen_ti1(/offset)
IDL> ycen=hdr->getycen_ti1(/offset)
IDL> print,xcen,ycen
       21.410865      -976.24575

3. I wrote a wrap idl program called "eis_getpinfo.pro" to get pointing information (no need to read full fits file)

IDL> fname='eis_l0_20070320_030501.fits.gz'
IDL> eispointing=eis_getpinfo(fname)
IDL> print,eispointing
       21.410865      -976.24575       583.06600       512.00000
The values mean: XCEN, YCEN, FOVX, FOVY (arcsec)

Any comments?

JianSun 22-Nov-2024 05:34