VLTI Visibility Calculator

Interferometry VisCalc Expert Mode Version P114
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NOTE 1: GRAVITY and MATISSE users should use the dedicated GRAVITY and MATISSE ETC for visibility calculations and their feasibility.

NOTE 2: The Shadowing in VisCalc is not up-to-date compared to the one used in GRAVITY and MATISSE ETCs.

NOTE 3: The baseline configurations in VisCalc are those valid up to P110. For the latest configurations, please refer to the VLTI Configurations Overview and to the GRAVITY and MATISSE ETCs.

Switch to Call for Proposal Mode

Target Definition

Target Coordinates:

 Declination:        deg min sec      Start:   HOUR ANGLE              Timespan:  hours
*Date & Time information required ->

 Right Ascension: hr min sec   Declination: deg min sec  Target Name:       Target name is passed to the Simbad Web App
Observation Date & Time Start (UT):
Year: Month: Day:
Hour: Min: Sec:
Timespan: hours
Epoch: 2000

Target Spectrum:

Uniform: Constant over wavelength range Blackbody Temp: kelvin Stellar Template Spectra: (* not suitable for Midi) Spectrum User Defined: Upload a spectrum file, should be an ascii file (*.dat or *.txt).

Target Geometry:

Single Disc: Diameter: mas Gaussian: FWHM: mas Gaussian: FWHM: Elliptical major mas minor mas angle deg Binary Discs: Angle: deg Angles counted from North to East Separation: mas Diameter, Primary: mas Diameter, Secondary: mas Brightness Ratio: Fits: Pixel Scale: mas
Supported formats: FITS images. Bits per pixel must be 32, Maximum pixel size 1000x1000. Angles counted from North to East.

Observation Setup

Wavelength Domain:

Filter: Bandpass: Central Wavelength nm FWHM: nm MultiWavelength: nm

Observatory Location:

Location Paranal:      Latitude: -24.62794830 Longitude: -70.40479659
    Offered configurations:
    All stations:

    VLTI Station Positions

    VLTI station layout
Location UserDefined: Latitude: Longitude:


Max. Target Airmass: Max. Sun Altitude: degrees


Time between UV points: mins Max delay line difference: ± metres


 All results 

 Show Input Parameters
 Show Input Target Image (fits file upload required)

 Delay Lines 

 Observation Time Window
 Target Altitude
 Target Azimuth
 UV Tracks
 UV Tracks (Over Fourier Transform)
 UV Tracks (Constant Shape vs Wavelength)

 Visibility Squared
 Loss of Correlated Magnitude
 Baseline Length
 UV Azimuth

 Phase - Map 2D
 Phase - Baseline Specific
 Phase - Triplet Closure

 Finito (AMBER only)


This software has been prepared in collaboration between ESO and the Jean-Marie Mariotti Centre