This week we don’t look at one of our light curves, but at where the HOYS fields are on the sky. This is shown in the above plot. While it looks quite boring, there are a lot of data in the figure. We have not just plotted a black square for each HOYS field. But indeed every single star.

In particular the plot is part of the preparation to improve the speed of data access in the database. As mentioned before, we plan to cross match all the measurements to the news data release from Gaia (Data release 3). In a first step we have downloaded all Gaia sources that are within a 1.5 x 1.5 deg square around each HOYS field. This size covers all potential stars in our images based on the largest camera we have data from. In total there are 3 million (!!!) stars in those fields, after one removes the double entries in overlapping regions.

Our data is typically less deep than Gaia. Gaia detects sources down to Gmag=21mag. This roughly corresponds the a limiting magnitude in the R-band of 21mag. Most of our data is not much deeper than 18th magnitude. We thus will limit the sources for potential cross-matching to Gmag brighter than 19th mag. Thus, it considers that we might detect some of the 19th magnitude stars when they vary by more than one magnitude. With this cut, there are only about 970,000 stars left. And this is what has been plotted in the figure.

As you can see, our targets fall roughly in the two groups Summer (left) and Winter (right). Maybe have some fun finding out which ‘square’ is your favourite field 😉 One can see, there is quite some overlap. The pair IC1396A/N (top left), the three fields PCyg, MWS3274, and Berkeley86, as well as several fields in Orion.