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Дата изменения: Unknown Дата индексирования: Sun Apr 10 20:07:51 2016 Кодировка: Поисковые слова: crab nebula |
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VLTI Calibrator Selector |
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The VLTI Calibrator Selector Tool is a tool intended to assist in the selection of suitable interferometric calibrators for VLTI observations with MIDI and AMBER. It uses a model of the VLTI and its instruments to assess the fringe visibility, given the observed bandpass, the geometry, spectrum, and coordinates of the target and the time at which the observations are to be made. It also takes into account shadowing by telescope structures and the maximum available stroke of the delay lines for the feasibility assessment of the observations.
The tool offers an HTML/Java based interface and consists of two pages. The observation parameters page presents the entry fields and widgets for the target spectrum and geometry, time of observation, instrument configuration and results selection. A "Submit" button submits the parameters to the model executed on the ESO Web server. The results page presents the computed results. The optional graphs are displayed within Java applets allowing interactive manipulation. The results are also provided in ASCII and GIF formats for further analysis and printing. Finally, a summary of the input parameters is appended to the result page.
In this section, the instrument and mode must be selected. Instrument description and additional information is available for VLTI.
Precision Integrated-Optics Near-infrared Imaging ExpeRiment.
Astronomical Multi-BEam Recombiner.
Disperser Description.
Beam combiner description.
Fringe Sensor description.
In this section, the spectrum and geometry of the target to be observed must be defined.
Given in hours, minutes, and seconds, or in decimal degrees
Given in degrees, arc-minutes, and arc-seconds, or in decimal degrees between -90 and +90 degrees.
The target name is resolved by Simbad. This service determines the coordinates of the target automatically.
Here you specify the target magnitudes, as needed.
J, H, K, or N band, needed to find matching calibrator.
Only needed if FINITO is to be used (fringe tracking in H band).
Magnitude of the target itself or its Coude offset guide star in V band to check feasibility of guiding.
Here you specify the uniform disk equivalent diameter of your target. This value is needed to predict visibility amplitudes of the target. A suitable calibrator would have amplitudes significantly larger than these to provide a reliable calibration.
Given in mas. For binaries, specify for the larger component.
Best suited for planning visitor mode observations on a specific date. In service mode, January is best for RA of 8h, then advance RA by 2h for each month, e.g. April for RA of 14h, July for RA of 20, October for RA of 2h.
Best suited for planning service mode observations on any date.
Best suited for planning service mode observations on any date.
Please select the telescopes of a baseline individually.
Range of angular distances to the target (in degrees).
Range of magnitude difference to target.
Range of calibrator diameters.
Various constraints on the calibrator spectral types.
Range of calibrator luminosity classes.
The quality flag depends on LDD_chi2.
Range of normalized visibilities. NB: Experimental!
Using the default values in the html input page an example of the calculations can be seen using the 'MAPLE' application
The web page takes into account the filter transmission, and uniform, blackbody and spectral target fluxes in calculating a weight average curve which is used to calculate the final visibility value.
Units: aU aV [metres] lambda [metres] double uCoord = aU/lambda; double vCoord = aV/lambda; double rho = sqrt(uCoord*uCoord + vCoord*vCoord);
Units: singleDiscDiam [radians] double uda = _pi*singleDiscDiam*fabs(rho); double vis = 2* fabs(j1(uda))/uda;
Bug fixes on the Observability Criteria. Gravity is now supported.
Telescope configurations updated for P96. Removed support for MIDI.
The instrument mode incorporates all available options in the drop-down list. The calibrator database is updated with the new JSDC v2 release (23.04.2014)
Update: a distance between target and calibrator might equal zero, in this case the calibrator appears twice on top of the resulting table.
All ETC version numbers have been aligned at 5.0.0 as the ETC system infrastructure was re-factored and installed on a new web server. Please report significant discrepancies to the ESO user support group usd-help@eso.org
New baselines for Period 90 have been added.
JMMC provided calibrator list (released 06 December 2011) is implemented.
It is now based on JSDC catalogue.
New interface for plots - the calibrator observability windows
are displayed as coloured background at any plot.
"Astrometric" mode is implemented. It gives access to the proper motions and paralaxes.
The algorithm to compute U,V,W has been made more accurate due to the use of CPL matrix multiplication.
Bugfix. All visible calibrators are displayed inside the table.
The new format of the observable time intervals is implemented.
A list of the intervals is displayed in the corresponding column.
Send comments and questions to usd-help@eso.org | ![]() |