Assesment of Gaia Guiding Stars

We use the Gaia database through the astroquery interface to generate sky fields with stars. For the Schmidt scale at the focal plane of 86.20 arcsec/mm and a typical guiding detector of size 4x4mm (e.g. a CMOS 1000x1000 pixels of 4micron each) the FoV to search for guiding stars at any one location on sky is 5.75’x5.75’. To study the availability of stars for guiding, we generate random locations on a sphere and select 10000 fields with declination above -22.78º (so that maximum airmass < 2). We then count the stars brighter than a given magnitud (Gaia ‘phot_g_mean_mag’). The figure shows the percent number of these fields with at least one guide star brighter than a given magnitude. Clearly, basically almost any 5.75’x5.75’ location on the sky has guide stars brighter than 16 mag, which guarantees that we can guide by having a single CCD located at the Focal Plane next to the IFU (credit: Enrique Pérez).