Welcome to the VLBA Calibrator Search Tool

The VLBA Calibrators List drives a search engine to find calibrators that are close to a specified position. Please fill out the VLBA Calibrators Search Form below. The search will return a table of sources within the search radius and a diagram showing the proximity of each source to the search center. Plots of the source visibility and image distributions are given for many sources.

Users are encouraged to use the NRAO helpdesk to get assistance identifying the optimum calibrator for their observations.

Users are encouraged to report any issues to the helpdesk. Users may also want to try the NASA VLBI Calibrator Search Tool.

Reset Values

RA:*

RA Formats: XX:YY:ZZ.ZZZ, XXhYYmZZ.ZZZs, XX YY ZZ.ZZZ, XX YY

DEC:*

DEC Formats: XX:YY:ZZ.ZZZ, XXdYY'ZZ.ZZZ", XX YY ZZ.ZZZ, XX YY

Search Radius (degrees):*

The maximum search radius is 45.0 degrees.

Maximum Number of Sources Returned:*

The maximum number of sources allowed is 100.

Minimum Flux Density (Jy):*

Select sources with short baseline (<400 km) flux density greater than or equal to the specified value at the selected observing band.

Observing Band:*

Additional Resources

The Calibrator list and accurate positions as a text file: Calibrator List
The Calibrator list and accurate positions as a SCHED .key file: Calibrator List (SCHED)

Major Catalogs

The ICRF3 VLBI Source Position Catalog: ICRF3 source list
The NRAO SCHED Source list using ICRF3 positions: ICRF3 SCHED calibrator list
The ICRF3 publication: Charlot et al. 2020
The Radio Fundamental Catalog (RFC): RFC
The RFC publication: Petrov & Kovalev 2025

Other Search Tools

NASA VLBI Calibrator Search Tool: VLBI Calibrator Search

VLBI Image Databases

NASA's Astrogeo VLBI image database: Astrogeo image search
The Bordeaux VLBI Image Database: BVID
The US Naval Observatory Fundemental Reference Image Data Archive: FRIDA