We have been developing a systematic effort to collect good quality images of the optical counterpart of ICRF sources, in particular for those that have been regularly radio surveyed either for future implementation at high frequencies and/or those that will be the link sources between the ICRF and the Gaia CRF.

To link the future Gaia CRF (at optical wavelength) with the ICRF (based on the VLBI observations of quasars at radio wavelengths) it is required to observe a set of QSOs which are visible in the optical domain. Only about 10% of the ICRF sources (∼ …

The goal of this paper is to examine the link between the defining radio reference frame (ICRF) and the optical reference frame (HCRF) by observing the optical counterparts of ICRF sources on the HCRF using theTycho-2as reference star catalog in a two-step process to bridge the large magnitude difference.

The Gaia CRF will be based on bright quasars (QSOs) with the most accurate coordinates, and will supersede the current International CRF (ICRF) which is based on Very Long Baseline Interferometry (VLBI) radio data.

2015年1月4日 · The most complete bank of optical images of the ICRF objects was created by Andrei et al. (2015 presented the 3rd release of the Large Quasar Astrometric Catalog (LQAC-3).

2019年2月1日 · LQAC3 contains all the known QSOs discovered in the 2dF/2QZ survey, the DR10Q of SDSS-III (Bolton et al. 2012; Pâris et al. 2014) and the VLBI QSOs listed in the ICRF2, VLBA, VLA and JVAS catalogs.

Between 1997 and 2004 several observing runs were conducted mainly with the CTIO 0.9 m to image ICRF counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to...

Optical astrometry of 12 fields containing quasi-stellar objects (QSOs ) is presented. The targets are radio sources in the International Celestial Reference Frame with accurate radio positions that also have optical counterparts.

The optical observations of QSOs are useful for photometry (SDSS, ugriz>BVR) and morphology tasks by using mentioned telescopes (and good CCD detectors); seeing=1.˝5 to 3.˝5, and 1.˝2 for 60cm ASV. Correct calibration (dark, bias, flat, +dead/hot pixels) and stacking.

To link the future Gaia CRF (at optical wavelength) with the ICRF (based on the VLBI observations of quasars at radio wavelengths) it is required to observe a set of QSOs which are visible in the optical domain. Only about 10% of the ICRF sources ($\sim$ 70 sources) are suitable for this task.