### 8 Accessing catalogues

8.1 FITS tables
8.2 TST
8.3 STL

Most of the CURSA applications prompt you to enter the name of at least one catalogue. You should reply with the name of the file containing the catalogue. The file name of a CURSA catalogue comprises the ‘catalogue name’ followed by the ‘file type’, for example:

perseus.FIT

where ‘perseus’ is the catalogue name and ‘.FIT’ the file type. The catalogue name is restricted to contain only: upper or lower case alphabetic characters (a-z, A-Z), numeric characters (0-9) and the underscore character (‘_’). The file name may optionally be preceded by a directory specification.

CURSA uses the ‘file type’ of the file name to determine the format of the catalogue (FITS table, TST or STL) and therefore the file name must end in the appropriate file type. The file types for the three catalogue formats are:

 FITS table: .FIT .fit .FITS .fits .GSC .gsc TST: .TAB .tab STL: .TXT .txt

The .GSC and .gsc file types for FITS tables are provided in order to allow regions of the HST Guide Star Catalog to be accessed easily. Other FITS tables obtained from an external source, such as those mentioned in Section 2, may have a different file type. They must be renamed (with the Unix command mv) to have a recognised file type before they can be accessed with CURSA.

A few additional details which are specific to the individual catalogue formats are described below. The peculiarities and limitations of the three catalogue formats are described in full in Appendix C.

#### 8.1 FITS tables

(File types: .FIT .fit .FITS .fits .GSC .gsc). Mixed capitalisations, such as .Fit, are also supported. To access a FITS table in the current directory you need only supply the file name. To access a FITS table in another directory you should precede the file name with an absolute or relative directory specification5.

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 can 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.

#### 8.2 TST

(File types: .TAB .tab). Mixed capitalisations, such as .Tab, are also supported. To access a TST (Tab-Separated Table) format catalogue in the current directory you need only supply the file name. To access a TST catalogue in another directory you should precede the file name with an absolute or relative directory specification.

#### 8.3 STL

(File types: .TXT .txt). Mixed capitalisations, such as .Txt, are also supported. To access an STL (Small Text List) format catalogue in the current directory you need only supply the file name. To access an STL catalogue in another directory you should precede the file name with an absolute or relative directory specification.

An input STL catalogue may be in either the standard form or the KAPPA variant form (see Appendix F). By default CURSA writes standard STLs. It can be made to write a KAPPA variant STL by appending ‘KAPPA’ inside curly brackets after the name of the file. For example, to write a KAPPA variant STL called perseus.TXT you would specify:

perseus.TXT{KAPPA}

KAPPA’ can be abbreviated down to just ‘K’ and can be given in either case. Also the closing curly bracket is optional.

5Of course, you can precede the name of a catalogue in the current directory with a directory specification if you want to, but there is no point in doing so.