How to create Finding Charts for Service Mode
In general, a finding chart has to be attached to each OB. Exceptions are possible for some instruments, in which case this is specified in the instrument-specific rules, which can be found by selecting the instrument from the pull-down instrument selector menu in the upper right of this web page.
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, e.g. 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 the parallactic angle)
Please verify that finding charts have sufficient quality and resolution. This can be done using p2 by attaching the finding chart and then clicking on the "thumbnail" version to see the full size version displayed in your browser.
Please read the P2 finding chart tutorial for a detailed description on how to attach finding charts to OBs.
How to create finding charts
p2 Finding Chart Generation service
A Finding Chart Generation service, called p2fc, is integrated into p2. It allows the automated, non-interactive creation of finding charts for individual or multiple OBs at the push of a button for almost all of the current VLT and La Silla instruments that require finding charts. A detailed description and instructions for usage are available in the dedicated p2fc Finding Charts page.
A command line interface to p2fc is also available, via the Python p2api, allowing control over many of the characterisitics of the FC generation that are not possible in the single click implementation available in p2.
Other Finding Chart tools
Alternatively, valid finding charts can be produced with any software tool able to produce output files in JPEG format. For users who do not use the p2 finding chart generation service or instrument specific preparation tools like FIMS or KARMA, ESO recommends the use of the SkyCat-based finding chart tool. This tool provides another user-friendly interface to easily produce finding charts with the general characteristics described above.
Skycat, including the ESO Finding Chart Plugin, is now available from the ESO software repositories (see below), package name eso-skycat.
Additional rules for VISIR finding charts
- Finding charts are to be provided based on existing infrared (K-band or longer wavelength) images. Typically, 2MASS 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 Obsprep tab in p2.
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.