FAQ, Hints, and Tips

version: 2003-01-15 oh

This page lists various hints, tips, and frequently asked questions. If you don't find a reply to your problem, pls contact us.

Content


I cannot read my CD / some data are missing from my CDs

If it is a recent observing run on a VLT-compliant instrument (i.e. with P2PP), you can send us (to lasilla@eso.org) a request. Pls be as specific as you can: we absolutely need the date of the nights and the instrument, and ideally the file name of the missing files. We'll produce a new CD and mail it to you.

If these are data older than a few month, obatained on a VLT compliant instrument, you will have to retreive the data from the Archive, at http://archive.eso.org/

If these data are from a non VLT-compliant instrument, send us a request at lasilla@eso.org.

I cannot read my tape...

The La Silla tapes are written with DDS3 (3d generation DAT), which is the standard for any unit less than 5-6 yr old. They are written in native density (no compression), unless you did something strange. The format is standard FITS, either directly as individual files or in Tar, depending how your wrote your tape.

The basic commands to read the tapes are:

Scripts to read a dd tape

If you have a tape that was written with dd (i.e. individual FITS files written to tape), you can read it directly to disk using this script: tape2disk. Ideally, it should be combined with RestoreID to rename the files to their original name (which is stored in the header). Download the scripts, edit them to adjust the name of your devices, and store them somewhere in your path for executables. For competeness, we also have a disk2tape script to write to tape. These scripts were written by James Brewer.

Conversion of ESO FITS headers to IRAF compatible headers

The FITS files produced by ESO instruments make extensive use of the hierachical keywords. Some image processing systems, including IRAF, cannot deal with them. To convert these keywords (e.g. from HIERARCH ESO TEL AIRM START to AIRMASS ) use the hierarch28 program developped by N. Devillard. This program, together with a series of other useful FITS-related programs, is available at http://archive.eso.org/saft. (They are part of the ECLIPSE package, and therefore directly available at the telescope and on any scisoft machine). Alternatively, ESO has developped a set of tools to deal more generically with the FITS headers, the FITS Translation Utility, or FTU, which is available from http://archive.eso.org/ftu

NTT: Active Optics and Image Analysis

Short version

Long version:

See the NTT active optics page

NTT: Observations at Zenith and Alt-Az Mount

The NTT has an Alt-Az mount; as a consequence, the singularity for the pointing is at Zenith, and not at the pole as it is on traditional equatorial mounts. When observing very close to the Zenith, the telescope, building, and instrument rotators have to rotate very fast to track the object. This will result in a poor image quality, unaccurate pointing and tracking, objects getting out of the slit, etc. In the worst cases, presetting too close to the Zenith can also crash the system.

To avoid any problem:

So, adjust your program taking this into account.

As a compensation, the NTT does not have a 6h limit on the hour angle, as on equatorial mounts: you can point below the pole at 12h HA.