Astroplate Wiki served in the initial phase o the APPLAUSE project for sharing know-how on digitization and preservation of astronomical photographic records.
Astroplate Wiki is a result of the AstroPlate Meeting 2014 in Prague, where many scientists from Europe, America, Asia came together to present their current efforts to digitize the photographic plates from a century of astronomical observations, or scientific work using the plates and digitized images. Software not only to annotate and publish images of the plates, but also to generate catalogs with astrometry, photometry and even spectroscopy of the celestial objects contained in the plates was presented.
Contributions on all issues related to photographic plates and films are welcome.
Please contact the project for suggestions & contributions.
Note: We have incorporated the original wiki into the APPLAUSE wordpress. All content remains unchanged from old wiki. Only occasional hints (e.g. that the FITS header version of the wiki has been revised in DR3) were added. A. Galkin, H. Enke, 02/2020, AIP
- Archives and preservation of photographic records
- Digitization process
- Handling of digitized data
- Data structure and file formats
- Lost and Found
Archives and preservation of photographic records
Acquisition of digital image data is the basis for building up a digital archive of photographic plates and films. This section is dedicated to sharing any information pertaining to this task. As digitization methods for plates can be different in some aspects from those for films, these methods are described here separately.
- workflow at the Leibnitz-Institute of Astrophysics Potsdam (AIP)
- workflow at the Dr. Remeis-Sternwarte Bamberg
- Digitization of photographic plates and films
Digital image data alone cannot be of much scientific use. Thus, all observational data available in any form has to be digitized as metadata, too. It will have different contents, depending primarily on the object and method of observation. Similarly, there can be different sources of metadata - observational books, plate indices, plate envelopes, hand-written notes on plates themselves, etc. - and all of them should be taken into account with high precision and accuracy in order to fill the gaps and to eliminate errors. Also, different levels of detailing in metadata can occur due to scarcity of sources, lack of man-power to compile metadata or for any other particular reason. Finally, the structure of metadata must match the requirements of software which will handle it later on. By these reasons different approaches to digitize plate metadata are possible. Nevertheless, there are attempts to create general standards. Below are descriptions of some metadata structures and their contents:
Handling of digitized data
Extraction of sources on direct images
The positions (Cartesian coordinates x,y) and the optical densities caused by the celestial objects on the photographic emulsion are extracted for each object on each plate using the program packages SExtractor and PSFEx. See also Tuvikene et al., 2014 and Tuvikene, 2014.
The astrometric calibration, i.e. the transformation of the Cartesian coordinates x,y from the plates into the celestial coordinates, RA and DEC, is carried out by a python package called PyPlate which is currently being developed at the AIP in Potsdam (see Tuvikene et al. 2014 and Tuvikene, 2014). This script combines the programs SExtractor, astrometry.net, and SCAMP, and uses astrometric data from the fourth U. S. Naval Observatory CCD Astrograph Catalog (UCAC4).
The photometric calibration will be done by applying a relation between the relative magnitudes derived from the plates to observed values from all-sky catalogs (see Tuvikene et al., 2014 and Tuvikene, 2014).
Data structure and file formats
Archives and digitization projects - APPLAUSE-constortium
Archives and digitization projects - other
Processing of digitized plate data
Science results - APPLAUSE-constortium
Science results - other
Lost and Found
Astronomical plates missing from a collection that that are being sought Astronomical plates found that do not belong to the observatory currently holding them