Autoslit is used to create slit-masks for the LRIS instrument from a list of object positions. Given an input file of object positions and a parameter file to control the operation of the program, Autoslit may be used to automatically and/or interactively match slits of various shapes to a selection of the objects. Autoslit will produce output files for the LRIS slitmask mill machine and the slitmask alignment program.
Autoslit was developed by Judith Cohen and Patrick Shopbell, but it is currently distributed and supported by W.M. Keck Observatory.
Autoslit and a number of support files are available via the URL:
Alternatively, the source may be retrieved and compiled locally. A Makefile is including for compiling Autoslit. The code should compile on most Unix systems, although it is currently developed on Mac OS X and RedHat Enterprise Linux hardware.
Autoslit is distributed as a gzipped tar file, that should be unpacked using the 'gunzip' utility from GNU and the Unix 'tar' utility:
> gunzip autoslit.tar.gz
> tar xvf autoslit.tar
Alternatively, the version of 'tar' from GNU includes an option to use 'gunzip' directly:
> tar zxvf autoslit.tar.gz
This process will create a directory, autoslit-3.x, which contains the source code and example input files for Autoslit.
This file contains parameters settings which control the behavior of Autoslit and define addition slit types. Autoslit will prompt the user for the name of this file.
The parameter file consists of two sections, with a structure as follows:
<keyword> <value>
<keyword> <value>
...
END
<slit definition block>
<slit definition block>
...
END
All words are case-insensitive, and spacing is not important.
The keyword-value pairs may be given in any order. The seventeen possible keywords are as follows:
FILENAME <name> - name of input object file
FILEOUT <name> - root file name for output files
PRIORITY <int> - object priority to divide objects
RANK_TOP [1|2] - number of slit ranks in top half
RANK_BOT [1|2] - number of slit ranks in bottom half
SLIT_WID <real> - width of slits in arc-sec
SLIT_LEN <real> - minimum length of slits in arc-sec
SLIT_SEP <real> - separation of slits in arc-sec
EPOCH <real> - epoch for slitmask use
TEMP <real> - temperature for refraction calc in Celsius
PRESS <real> - pressure for refraction calc in mm of Hg
WAVE <real> - wavelength for refraction calc in Angstroms
LAT <real> - latitude of observatory in decimal degrees
POS_ANGL <real> - position angle in decimal degrees
HOUR_ANG <real> - hour angle in decimal degrees
MIRROR <object> - use guide star [DEPRECATED in v3.20]
ENG_TEST <boolean> - engineering test?
ADC <boolean> - atmospheric dispersion corrector in use?
INTERACT <boolean> - interactive slit assignment?
VERBOSE <boolean> - verbose output?
For the values of the boolean keywords, any string beginning with one of the letters [tyTY] denotes true/yes, while any string beginning with one of the letters [fnFN] denotes false/no.
Autoslit 3.0 enables the use of four non-standard slit types: tilted slits, arc slits, line segment slits, and boxes. These slits are defined in the second section of the input parameter file. Definition blocks are structured as follows:
TILTS <int> <object> <pos angle> <min up> <min down> <object> <pos angle> <min up> <min down> ...
The first line specifies the number of tilted slits to be defined. Each subsequent line defines one tilted slit. Each slit is defined by the name of the object on which the slit will be placed (from the input object file), the position angle of the slit, and the minimum extent of the slit in arc-seconds, above and below the position of the object.
ARCS <int>
<name> <ra> <dec> <epoch> <radius> <min pa> <min pa>
<name> <ra> <dec> <epoch> <radius> <min pa> <min pa>
...
The first line specifies the number of arc slits to be defined. Each subsequent line defines one arc slit. Each slit is defined by a name (arc slits need not be placed on objects), the position of the center of curvature of the arc, the epoch of the center position coordinates, the radius of curvature, and the position angles of the ends of the slit. The RA and Dec of the center should each be defined by three numbers (hours|degrees, minutes, seconds), separated by whitespace. The radius should be positive for arcs to the right of the center, and negative for arcs to the left of the center. The slit will extend along the smallest arc between the specified position angles.
SEGMENTS <int>
<name1> <ra> <dec> <epoch>
<name1> <ra> <dec> <epoch>
<name1> <ra> <dec> <epoch>
<name2> <ra> <dec> <epoch>
<name2> <ra> <dec> <epoch>
<name2> <ra> <dec> <epoch>
<name2> <ra> <dec> <epoch>
...
The first line specifies the number of points to be defined for line segment slits. Each subsequent line defines one point in a line segment slit. Each point is defined by the name of the line segment slit (line segment slits are not placed on objects), the position of the point, and the epoch of the position coordinates. All consecutive line segment points which share the same slit name will be connected to form a single slit. For example, the above declaration would create two slits, one with 3 points (name1), and another with 4 points (name2). See the file Examples/test.in for more examples. Note that the value on the first line of the block indicates the number of points in the line segment slits, not the number of slits.
BOXES <int>
<object> <size>
<object> <size>
...
The first line specifies the number of box slits to be defined. Each subsequent line defines one box slit. Each slit is defined by the name of the object on which the slit will be placed (from the input object file), and the size of the box, in arc-seconds.
The order of the slit definition blocks does not matter. Multiple definition blocks are also allowed, i.e., two sets of arc slits. The only requirement is that the number of slit definition lines in any given block must match the number given on the declaration line, i.e., 'ARCS 4' must be followed by 4 arc slit definitions.
This file must contain one-line descriptions of each object of interest in the field, in a format identical to that used for Palomar Observatory's Norris spectrograph. This format is described in more detail in the file GET_OBJ.C, but is summarized as follows:
Each object description line consists of:
<name> <prior> <mag> <ra> <dec> <epoch> <equinox> <ra_pm> <dec_pm>
where
<name> = object identifier (or name)
<prior> = object priority as assigned by the observer
<mag> = object magnitude
<ra> = object right ascension: <hours> <minutes> <seconds>
<dec> = object declination: <degrees> <minutes> <seconds>
<epoch> = epoch of the object's coordinates
<equinox> = object equinox
<ra_pm> = object proper motion in right ascension in arcsec/yr
<dec_pm> = object proper motion in declination in arcsec/yr
Although the order of the fields is important, spacing between the fields does not matter.
The lines may be given in any order, *except* the first line, which should have a priority of '9999' and should provide the coordinates of the center of the field of interest.