FITS

File types: .FIT .fit .FITS .fits .GSC .gsc

Mixed capitalisations, such as .Fit, are also supported.

The .GSC and .gsc file types tables are provided in order to allow regions of the HST Guide Star Catalog to be accessed easily (see also Section ).

CURSA can read both binary and formatted FITS tables. It can write only binary FITS tables. It should be able to handle most components of FITS tables, with the exception of variable length array columns. If a variable length array column is encountered a warning message will be reported and the column will be ignored.

If a column containing no data is encountered a warning message will be generated and the column will be ignored.

In common with other Starlink software, CURSA does not support the COMPLEX REAL and COMPLEX DOUBLE PRECISION data types. If it encounters COMPLEX columns in a FITS table it represents them as follows:

• a COMPLEX REAL scalar column is represented as a REAL vector column of two elements,

• a COMPLEX REAL vector column of $n$ elements is represented as a REAL vector column of $2n$ elements,

• a COMPLEX DOUBLE PRECISION scalar column is represented as a DOUBLE PRECISION vector column of two elements,

• a COMPLEX DOUBLE PRECISION vector column of $n$ elements is represented as a DOUBLE PRECISION vector column of $2n$ elements.

Usually the table component of a FITS file occurs in the first FITS extension to the file. When reading an existing FITS file CURSA will look for a table in the first extension. In cases where the table is located in an extension other than the first you may specify the required extension by giving its number inside curly brackets after the name of the file. For example, if the table occurred in the third extension of a FITS file called perseus.FIT you would specify:

perseus.FIT{3}

The closing curly bracket is optional. When CURSA writes FITS tables the table is always written to the first extension.