Practical examples using the new NOT data formats

A consequence of the MEF data format is that during data reduction you will have to explicitly specify the number of the HDU you are interested in. Failing to specify the HDU number in IRAF will produce error messages like the following:
cl> imhe out.fits
out.fits: FXF: must specify which FITS extension (out.fits)

Example 1: List a header summary (the image name, dimensions, pixel type and object name) for the primary HDU using IRAF imheader:

cl> imhe out.fits[0]
uit[0][0][ushort]: NGC7790 Note the data dimensions for the primary HDU. They are [0][0], since there is no primary data array, only a primary header.

Example 2: How to display the first image extension:

display nc050062_notcam_mef[1]

Example 3: to display the third image extension

display nc050062_notcam_mef[3]

Example 4: Display all four MOSCA extensions at once in a mosaic

In stead of using the normal IRAF task display, we use mscdisplay from the IRAF MSCRED (Mosaic Reduction) package. If you have not done so already, first load the MSCRED package.

cl> mscred

The special mosaic task mscdisplay will display all available image extensions in a single display frame. You do not have to (and cannot) specify the extension number. The extensions are filled into a region of the display as defined by the DETSEC keyword in each extension header.

ms> mscdisplay mg240066_mosca 1 fill+

Example 5: Find astrometric reference stars

For all imaging data primary WCS information is included in the extension headers. Here we use mscgetcatalog to find coordinates and magnitudes for reference stars from Web-based catalog servers. The default catalog and server are USNO-A2 at NOAO, so this may take a few seconds. The task returns a text file of coordinates and magnitudes for a field centered on the reference coordinates from the WCS headers in the specified mosaic exposure(s). The syntax of mscgetcat is:
mscgetcat input-file ascii-outputfile
(For completeness the steps from the previous example are repeated).

cl> mscred
ms> mscdisplay mg240066_mosca 1 fill+
ms> mscgetcat mg240066_mosca.fits

When mscgetcat is finished, you can overlay the reference stars on the display:

ms> msctvmark 1 mark=circ rad=40 col=207

In your display window you should now see green circles close to the brighter stars. The positional match is not perfect, since the WCS information in the FITS headers is a first approximation based on the telescope pointing parameters only. It is the responsibility of the PI to calculate a proper astrometric solution, during data reduction.

MOSCA reduction notes

Reduction notes using IRAF mscred for MOSCA data in the new format are available.

Example 6: transform an image with multiple amplifier read-outs recorded as sections of a single image into multi-extension