Formal errors in the right ascension (times cosine declination, top) and declination (bottom) as a function of declination for the ICRF sources at G <  18.7 in Gaia DR2 and all sources in ICRF catalogs. In the right ascension the formal error is calculated as σ_α^* = σ_α cos δ. The shown formal error is the median of bins by every certain number of sources for the sake of clarity. The bin size was chosen to be 20 for the ICRF1, ICRF3 K-, and X/Ka-band, along with 50 for other catalogs.