IR data reduction: Lecture 3 Sarah Casewell :slc25@le.ac.uk Notes and presentations at: www2.le.ac.uk/departments/physics/people/academic-staff/slc25

•  www.le.ac.uk

Department of Physics & Astronomy

IRAF and xmosaic:

•  Reducing IR imaging data

•  Load up iraf in an xgterm (I prefer a scrollbar)

•  Load noao, imred, ccdred and xdimsum

•  Most preprocessing done in ccdproc

•  Mosaic done in xmoasic

Terminology

Imaging

Jitter/Dither/Offset

Imaging

1.  Sort out the frames according to their object types and exposure times: (hselect in IRAF, more in a non-resized terminal) 2. Subtract a bias frame (if you have one) from all other frames

3.  Investigate what sort of flat you have and process accordingly

4. Divide all remaining frames (arc, std, object) by the flat

5.  BPM subtract, Sky subtract, Mosaic

Imaging

6.  Astrometry

7. Photometric calibration and ZP determination

Things to watch out for:

Diffraction spikes

Charge bleed/saturation

Things to watch out for:

Diffraction spikes

Charge bleed/saturation

Image Ghost

Things to watch out for: Radial distortion

Things to watch out for: Radial distortion

Next week:

•  Workshop on IR spectroscopy

•  Will need to install starlink software •  Data available from here: /data/77/slc25/spectra_workshop

•  Workshop here:/data/77/slc25/spectra_workshop