Log of the two sets of SPHERE observations of HR 4796 A.
|Date||Set-up||DITa (s) ×||Par.||Seeing||Coh.||Wind||True||Platescaled|
|NDIT × NEXP||angleb (°)||(′′)||timec (ms)||(m/s)||northd (°)||(mas/pixel)|
|2014/05/19||IRDIS H||3 × 15 × 32||8.1; 39.3||0.8; 1.2||2.3; 1.0||10.5||−134.87 ± 0.6||12.238 ± 0.020|
|2015/02/02||IRDIS H2H3||32 × 8 × 14||−9.3; 39.4||0.6; 0.7||11||3||−134.155 ± 0.006||12.257 ± 0.03|
|IFS YJ||64 × 4 × 9||−33.65e ± 0.13||7.46 ± 0.02|
Parallactic angle at the start and end of the observations. For the April 2014 observations, not all the available field rotation was used (see Sect. 2 for details).
The coherence time τ0 is defined as τ0 = 0.31r0/v, where r0 is the Fried parameter measured by the DIMM and v is the maximum of the wind speed measured at30 m height, and 0.4 times the predicted wind speed at an altitude of 400 mbar (Sarazin & Tokovinin 2002).
The calibration of the true north and platescale are detailed in Maire et al. (2016). The true north indicated here includes the offset between the pupil-stabilised and field-stabilised mode.
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