**Table 2:** Comparison with other northern optical astrometric surveys.
	Optical astrometric survey		This paper
	Optical - ICRF		Optical - ICRF		No. of
Survey	$\sigma(\Delta$ $\alpha$ cos $~\delta)$	$\sigma(\Delta$ $\delta)$	$\sigma(\Delta$ $\alpha$ cos $~\delta)$	$\sigma(\Delta$ $\delta)$	common
	(mas)	(mas)	(mas)	(mas)	sources
ZZ	25	20	50	42	6
ZA nc	68	81	50	56	46
ZA co	69	81	50	56	46
SN HIP	194	236	54	57	41
SN TYC	177	152	54	57	41
SN ACT	154	158	54	57	41
FA A2	135	123	59	47	13
FA GSC	118	137	59	47	13

ZZ stands for Zacharias & Zacharias (2005); ZA co and nc refers to Zacharias et al. (1999) with and without galactic rotation correction, respectively; SN HIP, TYC and ACT stand for positions referred to the Hipparcos, Tycho and ACT catalogs from da Silva Neto et al. (2000); FA A2 and GSC refer to positions from Fienga & Andrei (2002) based on the USNO A2 and GSC 2.2 catalogs.

Source LaTeX | All tables | In the text