The PILMOS Software for VIMOS

What is PILMOS?

Recent upgrades to VIMOS have improved its stability and a detailed investigation into the accuracy to which slit positions could be predicted concluded that for many realistic observing programmes it would be possible to skip pre-imaging and directly produce the VIMOS MOS masks based on contributed catalogues. As of June 2012 Pre-ImageLess Multi Object Spectroscopy (PILMOS) is being offered as an option to VIMOS users.

To use the PILMOS mode, the contributed catalogues must have:

  • Very good (<0.2") relative astrometric precision for targets coordinates (RA,DEC) on a single astrometric
  • The list of targets must include some relatively bright reference stellar sources used to align the MOS masks.
  • Absolute astrometry must have <2" accuracy with respect to the guide star catalogue from which the guide star is selected.

The PILMOS observations have the following restrictions:

  • The slit width must be 1" or larger.
  • The position angle must be 90 degrees, or 0 degree for targets with -45<DEC<-5 deg (same rule as for MOS observations).
  • The airmass restriction is the same as for MOS observations: it is allowed to observe beyond +/-3h (if declination within -45<DEC<-5 deg and rotator at 0 deg) or +/-2h (if rotator at 90 deg) from the meridian.
  • No curved or tilted slits.

Observations that cannot be made within these constraints must use the conventional pre-image approach.

The observation preparation for PILMOS mode requires the use of the PILMOS tool for the selection of the suitable guide star and the guide probe orientation, and for creation of the fake pre-images and VIMOS catalogues that are then fed to the standard VIMOS mask preparation software VMMPS. If you want to change the names of the fake images and VIMOS catalogues please make sure that they still contain the string 'pilmos' in their names. Else, they are not valid.

The PILMOS tool is based on Guidecam, and differs only slightly from it. It is a Skycat-based tool that in addition to the standard functionality of Guidecam allows the user to upload his/her contributed catalogue, which contains accurate and precise coordinates of potential spectroscopic targets, and to transform it into a VIMOS catalogue suitable for mask design in VMMPS. In addition it generates four fake images, one per quadrant, that are used together with the transformed catalogue as input to VMMPS, and later for the finding charts.

Supported Platforms

As of Period 90, PILMOS tool is supported for Scientific Linux, but has been used successfully under other Linux operating systems (32-bit architectures). PILMOS is not available yet for 64-bit architectures.

Note about this release

PILMOS tool is shipped with the additional "Finding Chart" plug-in. Please note that PILMOS OBs must have a finding chart created with PILMOS tool attached, in addition to the 4 finding charts created with VMMPS, one per quadrant, showing the slits mask design. The finding charts must be based on the fake PILMOS images. Do not use true-sky images for the finding charts!

The Finding Chart plug-in allows you to superimpose the VIMOS detector footprint on your Finding Chart. Learn more about the plug-in in our Finding Charts cookbook.

PILMOS tool Installation

To install PILMOS tool, you will need to retrieve the tarball for your operating system, unpack it, and start the PILMOSt executable.

Please follow these steps:

  • Move to the directory where you want to install PILMOS tool.
  • Download the following tarball to the chosen directory:
  • Unpack the tarball gunzip -c pilmos-LinuxRH9-P90.tar.gz | tar xvf -

    This creates a directory structure that starts with:

  • Move to the pilmos directory cd pilmos-LinuxRH9-P90
  • Run the installation script and follow the instructions:./
  • Start-up the software ./pilmosLINUXRH9/bin/

    If the Guidecam main panel appears, and it has a PILMOS button, you have successfully installed the PILMOS tool. You can delete the compressed TAR file.

PILMOS User Guide

  • Users who wish to use VIMOS spectroscopic mode without pre-imaging (PILMOS) must read carefully the PILMOS User Guide included as Chapter 7 in the VIMOS User Manual.

Known features/bugs

  • If the magnitude column (containing the string 'mag' or 'MAG' as column description) is the last column of the catalog and is the only magnitude column, PILMOS does not display the targets in the 'fake' PILMOS finding charts. The work around is to just add another column to the catalaog that is not a magnitude column.
  • PILMOS might not work properly if the format of the column contents in the input catalog is not the correct one. For example, the ID column for reference objects require interger values.
  • After starting PILMOS and entering the pointing coordinates into it, no image is displayed and a dialog
    box pops up with the error message: ”Can’t find host IP address for: wvgarc” Normally it can be solved
    by restarting the tool. This is not related to the PILMOS functionality, but rather an issue of the regular
    Guidecam tool as well.

Instrument selector

This page is specific to VIMOS