How to create Finding Charts for Service Mode

In general, a finding chart has to be attached to each OB. Exceptions are given in the instrument-specific rules. Please read the P2PP3 User Manual for a detailed description on attaching finding charts to OBs.

General Finding Chart Requirements

Regardless of the instrument, finding charts must have all the following characteristics:

  • Clearly indicate the Observing Run ID.
  • Clearly indicate the PI Name.
  • Clearly indicate the OB Name or Target Name, as used in the OB to which it is attached.
  • The target(s) position(s) must be clearly indicated.
  • The entire instrument field-of-view must be shown.
  • North and East must be clearly indicated.
  • The scale must be indicated by drawing a bar and writing the bar length in arcseconds or arcminutes.
  • The wavelength range of the image must be indicated. Whenever possible, finding charts should have similar central wavelength to observations (e.g. DSS charts are often inappropriate for IR observations near the galactic equator).
  • The images should be negative, i.e. dark objects on light background.
  • The output files must be in JPEG format and their size must be less than 1 Mbyte.
  • Positions of spectroscopic acquisition reference stars, if any, should be marked.
  • Spectroscopic finding charts must indicate the slit(s) position(s) clearly (unless slits are aligned along parallactic angle)

Please verify that finding charts have sufficient quality and resolution. This can be easily done from within P2PP by using the View Finding Chart option in the Finding Charts menu of the main P2PP interface (see also the P2PP User Manual).

Skycat Finding Chart tool

Although in most cases valid finding charts can be produced with any software tool able to produce output files in JPEG format, ESO recommends the use of the SkyCat-based finding chart tool. This tool provides a user-friendly interface to easily produce finding charts with the general characteristics described above.


Additional rules for VIMOS finding charts

In addition to the general requirements for finding charts, the following requirements should be fulfilled.

All VIMOS imaging (IMG_), pre-imaging (PRE_), and IFU OBs must have one finding chart attached to them. The MOS and PILMOS OBs must have 5 finding charts attached to them, four showing the slits and the mask design (prepared with VMMPS) and the last one showing the guide star and the guide probe orientation (prepared with GuideCAM).

VIMOS specific requirements for VMMPS and PILMOS users:

  • The user-selected reference stars have to be identified and the slit alignment checked by the service mode observer interactively. Therefore, the VMMPS tool must be used for the generation of finding charts in MOS and PILMOS mode (the focal field setup can be displayed over the pre-image or PILMOS fake image via the VIMOS-MPS -> Verify ADP File menu in VMMPS).
  • One finding chart per quadrant needs to be produced and attached to the corresponding OB(s). The finding charts prepared with VMMPS must comply with the general specifications (see above). The finding chart plugin distributed with the VMMPS software provides a convenient way to do so.
  • The valid VMMPS-based finding chart should have the slit configuration overplotted (using the Plot Slit button in VMMPS).
  • VMMPS-based finding charts must be saved in jpeg format from the VMMPS File -> Make finding chart... window and must contain an overlay of the full VMMPS field clearly showing the reference stars and the slit geometry. The high resolution image generated in this way will allow to verify at the telescope the successful acquisition of the objects in the slits.
  • In the case of Pre-ImageLess Multi Object Spectroscopy (PILMOS) the finding chart has to be based on the fake images created by the PILMOS tool. Please do not use other true-sky images!

VIMOS specific requirements for imaging and pre-imaging runs:

  • The Guidecam tool with its convenient finding chart plugin must be used for the generation of finding charts in imaging and pre-imaging mode. The guide star should be clearly indicated in the finding chart.

VIMOS specific requirements for IFU users:

Since the target to be observed cannot be seen in an acquisition image once the IFU has been deployed, it is often difficult to assess whether or not the telescope is presetting to the desired position. For this reason, the following is required:

  • A 5' x 5' Digitized Sky Survey view of the field centered on the preset coordinates of the telescope. The field of view of the chosen IFU mode should be clearly indicated on the chart, together with the the distance between the center of the IFU field of view and the closest visible star. The requirement of using the DSS is mandatory, and motivated by the need to ensure that all the objects in the finding chart can be identified in the Guidecam display used at the telescope.
  • The finding chart plugin to SkyCat provides a convenient way to prepare ESO-compliant finding charts also for IFU users.

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