If you use this data, please acknowledge: "This work made use of the HDAP which was produced at Landessternwarte Heidelberg-Königstuhl under grant No. 00.071.2005 of the Klaus-Tschira-Foundation."
The data in this service was calibrated using Astrometry.net, 2010AJ....139.1782L.
To the extent possible under law, the publisher has waived all copyright and related or neighboring rights to the HDAP scans. For details, see the Creative Commons CC0 1.0 Public Domain dedication. Of course, you should still give proper credit when using this data as required by good scientific practice.