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Data Transfer

Reading your data into IRAF

To read your data into IRAF you need the images in FITS format. If you are not at the Observatory you need a tape of the images in FITS format. If you are working at the Schmidt, you can transfer images directly as follows.

On the FLAIR PC you can convert your images to FITS format using the local programme fitsout2. This is described in the FLAIR PC Guide (note that fitsout2 is an improved version of the original fitsout described). Note that the files are still not in legal FITS format and need correcting (see below). The images may then be transferred to whichever computer you use for the subsequent analysis using ftp:

$ ftp aatssa
username
password
binary
mput *.fts
bye

The final step is to convert the FITS images into IRAF images using the IRAF task rfits. This same command may be used to read both FITS tapes and FITS images on disk:

rfits dir/*.fts 1 flair    # disk example
rfits mta 1-999 flair      # tape example

Fixing the image headers: fixhead

The image headers as written by the FLAIR PC contain some entries not recognised by IRAF. For example, the date needs to be in the format dd/mm/yy rather than dd:mm:yy. The task fixhead corrects this automatically. It also performs a number of other useful functions: correction of UT for each image, changing R.A. and Dec. to that which is desired, and setting the epoch. The changes made are as follows. The package astutil must be loaded before running fixhead.

  1. The image is copied to a new file with a name formed by concatenating the specified ``root'' name with the original run number and a guess is made at the imagetype (object or zero) based on the title.
  2. The format of the date is corrected and the UT and ST are determined.
  3. The RA and Dec are corrected if desired and the epoch is entered.
  4. The image is reflected in the x-direction to give the same sense as displayed on the FLAIR PC system.
  5. If desired, the images can be corrected for large values which give negative values. This arises because the fitsout program on the PC writes non-standard unsigned 16 bit integers. These are interpreted by the IRAF rfits task as standard signed 16 bit integers, so values greater than 32767 come out negative. The task corrects this (slowly) by creating a new signed 32 bit image after adding 32768 to any negative pixels.
  6. If space is limited the original images may be deleted, but this is not recommended as these serve as a useful backup.
lparam fixhead  # An example set of parameters for the task fixhead
       images = ../raw/*.imh    Image(s) to fix
        (root = "flair")        New root name
   (changecor = no)             Change RA and Dec?
          (ra = 12.45)          New RA
         (dec = 13.5)           New Dec
       (epoch = 1950.)          Epoch
      (fixpix = yes)            Fix negative pixels?
      (remove = no)             Remove original files?
        (show = no)             Print operations?
     (imglist = "")             
        (mode = "ql")

At this stage a printed list of the images may prove useful:

imhead flair*.imh long- | lprint



next up previous contents
Next: Basic CCD Reduction Up: FLAIR IRAF Guide Previous: Setup

Mon Aug 19 16:47:38 EST 1996