Query constraints
The query interfaces can be used to display or to download data according to the query constraints that a user can set on any field. On all query forms, the button “Syntax Help” brings the user to the documentation describing how a query constraint can be formulated.
Most typically the user will want to retrieve measurements related to a specific time range; to achieve this, the user must type an interval in the Date field, using the range operator “..” For example: 2016-04-01..2016-05-01 can be used to retrieve the data for the entire month of April 2016.
Use the checkbox on the right of the parameter name to either include or exclude that parameter from the ouput result set.
Output preferences
At the top of any query form the Output preferences panel can be used to set the following properties:
- Output format, one of:
- html table (default)
- ascii fixed length/display
- ascii fixed length/download
- ascii csv/download (comma separated values)
When a download option is chosen, the browser will not show the results on screen, and instead it will prompt the user to either save the results in a file, or to use an helper application to open the results into.
To be noted that in “ASCII fixed length” output mode the null values are replaced by the string N/A.
- Return max rows:
- The query interface limits to a maximum of 15,000 the number of records returned when the user chooses to display the results within the browser (and not to download the data); if instead the user specifies a download mode (e.g. csv/download), or the query is executed programmatically (e.g. using curl or wget) then the maximum number of returned records is set to ten million. The user can change the default behaviour by setting the “Return max rows” to a lower number.
Query parameters common to all Paranal query forms
| This section provides
information on the common query parameters used in the La Silla ambient and meteorology query forms.
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| Date time |
The date time (UTC) when the data measurement has started (aka, start time).
To query it is possible to specify a range
in date or datetime, or an operator ( < > ) as shown in the examples here below:
- 2016-04-10..2016-04-12 (for a 2-day interval)
- 2016-04-10T18:00..2016-04-11T02:00 (for a 8-hour interval)
- >2016-04-28 (for an open-ended interval)
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| Integration time |
Timespan used for measurement of ambient data sample [s].
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| Monitor |
Link to the ambient monitor interface. Note that the displayed time interval starts at 21:00 on the graphs.
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 - More |
If you are in tabular mode and you wish to display the full individual record of a matching source, click on the appropriate magnifying glass in the query result page.
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Ambient The ESO seeing monitor (DIMM2) was installed in March 1991, on a 5m high tower, close to the Schmidt telescope as part of the permanent Astronomical Weather Station (AWS). Routine operation started in September 1991 and full automation was reached in December 1993. Seeing measurements were initially conducted from Cerro Vizcachas, 7km to the East of La Silla, and once candidate site for the VLT, from Oct. 1988 to Feb. 1991. As part of the same ridge, Vizcachas and La Silla present similar seeing conditions.
The seeing is defined as the Full Width Half Maximum of a stellar image observed with a perfect large telescope, at 500nm wavelength and at zenith. It is measured over periods of a few minutes all night long. Maximum wind speed for operation is about 18m/s and sky must be clear in the zenith area.
| DIMM-Airmass |
Airmass at which the ASM-DIMM telescope measures the site seeing.
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| DIMM-Seeing |
Observatory site seeing as measured by the ASM-DIMM telescope, Full Width Half Maximum at 500nm [arcsec].
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| RA |
The right ascension of the target star at which the ASM-DIMM telescope measures the site seeing [deg].
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| DEC |
The declination of the target star at which the ASM-DIMM telescope measures the site seeing [deg].
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Meteorology The Vaisala meteorological station was installed at La Silla in February 1985, it includes, on a 30m high mast, a number of sensors. The on-line database started storing data on January 1st, 1994. The following measurements are provided: Wind speed and direction, Temperature and Humidity.
The meteorological stations compute and store average, root mean square and extrema of each parameter during a preset averaging period (20 minutes). The sampling intervals are 2 seconds for digital sensors (wind speed and direction) and one minute for analog sensors (T, Rh, P). One minute averages are ingested into the database.
| Main parameters: | Air pressure, temperature, humidity, wind direction and speed at different heights. |
| Time coverage: | December 1993 onwards. |
| Access | the La Silla  La Silla Meteorology query form. |
| Air Pressure |
Temporal mean of observatory site ambient baromeric air pressure measured at sensor position 2m during measurement period [hPa].
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| Air Pressure Normalised |
Temporal mean of observatory site ambient air pressure normalised at sea level [hPa].
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| Ambient Temperature |
Temporal mean of observatory site ambient temperature measured at sensor position 30m, 2m and at ground during measurement period [C].
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| Dew Temperature |
Temporal mean of observatory site dew temperature measured at sensor position 2m during measurement period [C].
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| Relative Humidity |
Temporal mean of observatory site relative humidity measured at sensor position 2m during measurement period [%].
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| Wind Direction |
Temporal mean of observatory site wind direction measured at sensor position 30m and 10m during measurement period (deg 0-360).
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| Wind Speed |
Temporal mean of observatory site ambient wind speed measured at sensor position 30m and 10m during measurement period [m/s].
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![[ ESO ]](/images/eso-logo.gif){kind=logo}