PWT Data Reduction

The ST8CCD produces standard FITS files, which can be reduced and analysed with your favourite data reduction package. There are some guidelines here if you want to use the ccdred package with IRAF

IRAF ccdproc configuration files

The noao.imred.ccdred package contains several tasks to reduce CCD data. It needs additional configuration files to recognise the FITS header parameters used by the PWT. The configuration file is attached here as pwt.tgz. This should be extracted to (depending on your IRAF configuration) /iraf/iraf/noao/imred/ccdred/ccddb/. If you do not have write access to this location (e.g. on department desktop macs) you can put the files in a different location (e.g. /home/username/iraf/ccddb/) and tell IRAF to look in this folder.

To setup ccdproc for the PWT-ST8, within IRAF, do

noao
imred
ccdred
epar setinstrument   
(within the parameter list, set
instrument=st8
site=pwt
query=st8
directo=/home/username/iraf/ccddb/  (or where you put the pwt.tgz contents)
)
:go  (opens up a new parameter list -- nothing to change here)
:q  (opens up another new parameter list -- shouldn't need to change anything here)
:q

You should now be able to run the ccdproc tasks on PWT ST8 data. To test the header parameters are translated correctly, within iraf do;

ccdlist *.fts

and you should get something like;

ccdred> ccdlist *.fts
PSNJ0851+7150-S001-R001-B.fts[765,510][ushort][object][B]:PSNJ0851+7150
PSNJ0851+7150-S001-R001-R.fts[765,510][ushort][object][R]:PSNJ0851+7150
PSNJ0851+7150-S001-R001-V.fts[765,510][ushort][object][V]:PSNJ0851+7150
PSNJ0851+7150-S001-R002-B.fts[765,510][ushort][object][B]:PSNJ0851+7150
PSNJ0851+7150-S001-R002-R.fts[765,510][ushort][object][R]:PSNJ0851+7150
PSNJ0851+7150-S001-R002-V.fts[765,510][ushort][object][V]:PSNJ0851+7150
PSNJ0851+7150-S001-R003-B.fts[765,510][ushort][object][B]:PSNJ0851+7150
PSNJ0851+7150-S001-R003-R.fts[765,510][ushort][object][R]:PSNJ0851+7150
PSNJ0851+7150-S001-R003-V.fts[765,510][ushort][object][V]:PSNJ0851+7150

Where the exposure type (i.e. "object/flat/dark/zero") and filter are identified.

Reducing data with ccdproc

To get help on ccdproc, in IRAF do;

help ccdproc

The main tasks to use are;

• zerocombine - combine bias (zero) files to make a master bias
• darkcombine - combine dark files to make a master dark (including exposure scaling if needed)
• flatcombine - combine flat files to make a master flat (separates filters to make a flat in each filter)
• ccdproc - process frames depending on which flags are set (by default, bias and dark subtract, and flat divide)
• combine - combine images together (can separate filters to make image in each filter)

BEWARE! ccdproc does not deal with different ccd binnings (i.e. 1x1 and 2x2). You must separate data with different binnings manually and process them separately.

Example

To add...

-- FraserClarke - 24 Jan 2014