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).

NEW: Unified Guidecam tool for Finding Chart preparation

VIMOS, VISIR, MUSE and HAWK-I users shall use the unified Guidecam tool (GUCT) to prepare ESO-compliant Finding Charts. Using GUCT will also allow to directly connect to P2PP and upload the Finding Chart(s) to the OB(s) in preparation.

Other Finding Chart tools

Alternatively, valid finding charts can be produced with any software tool able to produce output files in JPEG format. Users who do not use the new unified Guidecam tool, 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 VISIR finding charts

  • Finding charts are to be provided based on existing infrared (K-band or longer wavelength) images. Typically, 2MASS or DENIS K-band images are acceptable, although higher spatial resolution is preferable. 
  • If the wavelength at which the finding chart has been taken is different from that of the science observation, e.g. a K-band finding chart for a N-band spectroscopic observation, the user has to clearly describe how to identify the target at the wavelength of acquisition in the README section of the programme description. Adequate examples of such comments can be:
    • the sources is the brightest source in the field of view in N-band or
    • two bright sources are expected in our field of view. The science target is the southernmost of the two.

Finding Charts for VISIR observations which are compliant with the above additional rules can easily be prepared using the new unified Guidecam tool (GUCT).

High-Resolution Spectroscopy OBs

The operating range in ADUs of the new Aquarius detectors is relatively small. Therefore, for high-resolution spectroscopy, the Detector Integration Time (DIT) needs to be optimized by the night-time astronomer for a given wavelength. It is therefore important that he wavelength(s) of scientific interest need to be clearly indicated in the README information, and by means of a plot of the Exposure Time Calculator (ETC) transmission spectrum, attached as an additional Finding Chart to the OB. If the wavelength(s) of interest are different from the central wavelength, this needs to be clearly indicated in this plot.

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