Table 1: VLT/NACO observation log and astrometric calibration results from HIP 73357.
Epoch Date of No. (a) FWHM Re- Pixel scale in [mas/pixel] Detector orientation in [$^{\circ}$]
year observation images [mas] mark value and abs. err. change and rel. err. value and abs. err. change and rel. err.
2004.48 25 Jun. 2004 27 64 (b) $13.23 \pm 0.05 $ (b) $0.14 \pm 0.25$ (b)
2005.40 27 May 2005 18 74   $13.240 \pm 0.050$ $0 \pm 0.001$ $0.21 \pm 0.33$ $0 \pm 0.007$
2005.60 7/8 Aug. 2005 15 63 (c) $13.250 \pm 0.052$ $0.010 \pm 0.002$ $0.35 \pm 0.34$ $0.146 \pm 0.014$
2006.14 22 Feb. 2006 15 66 (c) $13.238 \pm 0.053$ $-0.002 \pm 0.003$ $0.18 \pm 0.35$ $-0.024 \pm 0.020$
2006.38 20 May 2006 15 100   $13.233 \pm 0.055$ $-0.007 \pm 0.006$ $0.39 \pm 0.36$ $0.184 \pm 0.028$
2006.54 16 Jul. 2006 15 73   $13.236 \pm 0.055$ $-0.004 \pm 0.005$ $0.43 \pm 0.36$ $0.221 \pm 0.031$
2007.13 19 Feb. 2007 15 110 (d) $13.240 \pm 0.059$ $0.000 \pm 0.010$ $0.34 \pm 0.38$ $0.128 \pm 0.044$
Remarks: for each VLT/NACO observation, we list the pixel scale determined with its absolute error and the change in pixel scale since the first new observation (2005.4), always with the same astrometric standard star HIP 73357; same for detector orientation in the last two columns.
(a) Each image consists of 200 exposures with 0.347 s each, for both GQ Lupi and the astrometric calibration HIP 73357. (b) Results from 2004.48 as in N05, no relative errors available, because another astrometric calibration binary was observed. (c) GQ Lupi A in a non-linear regime (not saturated). (d) GQ Lupi A and HIP 73357 A in a non-linear regime (not saturated). Calibration (for 19 Feb. 2007 GQ Lupi data) obtained on 1 Mar. 2007 with HIP 73357, see footnote 1.


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