Mean plate scale and true north orientation for the SPHERE commissioning runs measured on the 47 Tuc field-stabilized observations in the IRDIS images in the H23 filter pair obtained with the APLC coronagraph (Sect. 2).
|Com. date||Plate scale (mas/pix)||True north (°)||Plate scale (mas/pix)||True north (°)|
|July 2014||12.252 ± 0.006||−1.636 ± 0.013||12.247 ± 0.006||−1.653 ± 0.005|
|August 2014||12.263 ± 0.006||−1.636 ± 0.013||12.258 ± 0.006||−1.653 ± 0.005|
|October 2014||12.259 ± 0.006||−1.788 ± 0.008||12.254 ± 0.005||−1.795 ± 0.008|
Notes. To align the IRDIS science images so that north is oriented up and east left, an offset accounting for the zeropoint of the derotator in pupil-stabilized mode of 135.87 ± 0.03° has to be added to the parallactic angles indicated in the fits header. This offset is measured on data of 47 Tuc acquired in July 2014 in both stabilization modes and assumed to be constant between the runs. For the astrometric calibration of the IFS science images, an additional offset accounting for the relative orientation between the IFS and IRDIS fields of −100.46 ± 0.13° also has to be added. This value is measured on simultaneous data of distortion grids of both instruments.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.