Solar Observatory Einstein Tower: Data Release Of The Digitized Solar Full-Disk Photographic Plate Archive

We present solar full-disk observations that were recorded at the Einstein Tower during the years 1943-1991 (solar cycles 18-22). High-school students from Potsdam and Berlin digitized more than 3,500 full-disk images during 2-3-week internships at Leibniz-Institut fur Astrophysik Potsdam (AIP). The digital images cover a 15 cm x 15 cm region on photographic plates, which were scanned at a resolution of7,086 x 7,086 pixels. The raw data are monochromatic 8-bit images in the tagged image file format (TIFF). These images were calibrated and saved with improved photometric precision as 16-bit images with2,048 x 2,048 pixelsin the Flexible Image Transport System (FITS) format, which contains extensive headers describing the full-disk images and the observations. The various calibration steps include, for example, accurate measurements of the solar radius, determination of the limb-darkening function, and establishing an accurate coordinate system. The contrast-enhanced and limb-darkening corrected images, as well as the raw data, are freely available to researchers and the general public in a publicly accessible repository. The data are published as a special data release of the Archives of Photographic PLates for Astronomical USE (APPLAUSE) project.