Conventions

Image Center

By default, VIP routines are compatible with either even- or odd-dimension input frames. For VIP routines that require the star to be centered in the input images (e.g. post-processing routines involving (de)rotation or scaling), the code will assume that it is placed on (zero-based indexing):

• size/2-0.5 for odd-size input images;

• size/2 for even-size input images;

i.e. exactly on a pixel in either cases. The VIP recentering routines will place the star centroid at one of these locations accordingly.

Position angles

In VIP all angles are measured counter-clockwise from the positive x axis (i.e. trigonometric angles), as all packages it leverages upon, including for the position angles retrieved when characterizing directly imaged planets. This is different to the typical astronomical convention to measure angles east from north (just add +90deg to angles returned by VIP).

4D IFS+ADI cubes

For all routines compatible with 4D IFS+ADI cubes, the convention throughout VIP is to consider the zeroth axis to correspond to the spectral dimension, and the first axis to be the temporal (ADI) dimension.