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Starting up

The commands in the Optopus package have to initialised by setting the Optopus context with the MIDAS command SET/CONTEXT OPTOPUS. All commands in this package have the qualifier OPTOPUS. Since the majority of them need quite a number of input parameters, and where their correct order and meaning is not always easy to remember, there are are two ways to enter command parameters. Besides the usual way of writing for each command:
command/qualifier p1 p2 p3 ...
it is also possible to define them in an explicit form:
SET/OPTOPUS param=value [param=value],
where param is the parameter name and value is the assigned value. Every parameter set in this ways can be defaulted on the command lines. Only the input and output filenames are required unless the general default names are used (see documentation of the individual commands). However, before executing a command it is recommended to check the session parameters by listing them with the command SHOW/OPTOPUS. This will produce an output table like in Table H.1. For a complete overview see Section H.3.2.

Table H.1: Parameters listed by SHOW/OPTOPUS
Input file: mytab1.tbl
Output file: mytab2.tbl
Plate label: SA94
Plate center: R.A.: 02h 43m 30.000s DEC.: -00d 15' 50.00"
Equinoxes: Old : 1950.00000 New: 1991.76776
Date: Year: 1991.00000 Month: 10. Day: 9. Epoch: 1991.76776
Exposure time: 120.0m
Wavelength range: from: 4000. Ångstrom to: 8000. Ångstrom
Optimal sid. time slot: from: 1h 0m to: 3h 0m
Optimal sid. time: 0.00h

The assigned values are maintained until the user gives the MIDAS command
CLEAR/CONTEXT or decides to leave the MIDAS session. However, is is possible to save them with the command SAVE/OPTOPUS table, where table is the name of any table chosen by the user. SAVE/OPTOPUS saves the relevant session parameters by copying them to descriptors of table. It is advisable to use this command, not only when you want to interrupt a session and restart it later, but again during the session to protect yourself against system crashes or accidental logouts of MIDAS. When re-entering Optopus context, all parameters are re-initialised to the default values but they can be re-set to the values of a previously saved session with RESTORE/OPTOPUS table, where table is of course the name of the table that contains the saved setting.

Since almost all commands in the package work, both in input and in output, on MIDAS tables, another important task of the user at the start of an Optopus session will be to create a MIDAS table from the ASCII file where the data about the objects to be observed are being kept. The newly created table will have to contain, amongst others, an :IDENT and a :TYPE column, where :TYPE contains ``B'' or ``S'', respectively for ``big'' and ``small'' guidestars, and ``O'' for scientific object. As the format of this table is fixed and crucial for all the following operations, there is a dedicated command for this purpose:

CREATE/OPTOPUS inp_file [out_tab] [fmt_file] [old_equinox]
A standard fmt_file can be seen in Table H.2.

Table H.2: Example format file
define/field 1 16 c a16 :ident  
define/field 18 19 d f2.0 :ahr "hours"
define/field 21 22 d f2.0 :amin "min"
define/field 24 29 d f6.3 :asec "sec"
define/field 33 33 c a1 :sign  
define/field 34 35 d f2.0 :ddeg "degrees"
define/field 37 38 d f2.0 :dmin "arcmin"
define/field 40 44 d f5.2 :dsec "arcsec"
define/field 48 48 c a1 :type  

A copy of this format file will be put in the working directis available in the file:

so that it can be copied to the user's working directory and subsequently modified according to the positions and field widths in his/her ASCII file. You can copy the format file into your working directory with the CREATE/OPTOPUS command itself. To do so give the third parameter fmt_file in the command the value copy. However, a copy will not be made if a file with the name opto.fmt is already present.

In case the targets are already stored in a MIDAS table the user should check if the table columns have the correct labels. If required, modifications in the table can be made by using one or more commands for table manipulation.

The equinox of the data has to be stored in the descriptor TABEQUI of the MIDAS table. It is important to verify whether the equatorial coordinates have been precessed or not. In fact, next step in this ``building-up'' of the Optopus session is the command:

PRECESS/OPTOPUS [inp_tab] [new_equinox],
which corrects the right ascension and declination for precession to the date of the observation (this is the default, which can be changed by defining the parameter NEWEQ), and updates the value of the double precision descriptor TABEQUI. To limit the number of files created in an Optopus session, this command will not to create a new table, but will add two new columns :RA and :DEC in the table created by CREATE/OPTOPUS. The old columns :RA and :DEC are renamed to :OLDRA and :OLDDEC, respectively. Note, that in this table the equatorial coordinates are in decimal format.

next up previous contents
Next: The Optopus session Up: Using the Optopus Package Previous: Using the Optopus Package
Petra Nass