Astrophysics

Photographic Plate Collection Laboratory

In México part of the sky surveys was carried out mainly with the astronomical plates that were taken by the Schmidt Camera of the National Astrophysics Observatory. For decades, great discoveries were made through those observations and analysis of these plates.

Nowadays the employ of astronomical plates has been abandoned due to the use of other recording techniques for observations such as CCD cameras; however, the fact that the astronomical plates are no longer used as storing devices of images does not imply that its importance was lost, but on the contrary, the astronomical plates of INAOE were sky studies taken during 50 years which have plenty of historical information. These plates are being sheltered in a place under controlled conditions of temperature and humidity at INAOE. Not many people have access to the plates due to the fact that they are very fragile. Only a few trained researchers are allowed to make use of them.

In order to avoid the loss of historical astronomical data, the Institute has been working on the preservation of the original plates by digitalizing them. Today, many observatories that used astronomical plates are generating their own image databases with the purpose of preserving and sharing their information. They are also focusing on the creating of programs to analyze information; an example of an image database project can be seen at the website: http://www.hs.uni-hamburg.de/surveys.html; Simbad-Aladin. This project will analyze the automatic study in which spectrophotometry is applied to different sky regions.

The intention of this laboratory is to design a program that automatically extracts digitalized images and spectra, identifies the coordination of objects, determines their exact position and identifies spectral lines; both emission lines and absorption lines, depending on whether we study stars or galaxies. For line identification, the program will do a sky extraction, find that plate’s characteristic curve and calibrate wavelength and flux.

Importance of the astronomical images database

An image database with these characteristics would be the first one of its kind in our country; we are the only observatory that has astronomical plates.

Astronomical Images Database

The astronomical image database will be a manager that will work as a storage place for tables of and image plates. Tables of data contain specific astronomical plate information and their central objects. Plates include data of emulsion type, data and time exposition and their central objects. Tables of the plate’s central object include the name and the coordination of objects, speed data, spectral time and other information. The images also present size and format information.

Automatic Spectral Extraction

Photographic plate studies are very difficult to develop, due to the nature of emulsions; the results are often not satisfactory. However, the information obtained from them, especially from spectral plates, can be very useful for sky mapping where variable objects can be found.

Advances

An assisted computer program has been created in the development stage, it is able to provide a digitalized image’s spectra and identify it according to the program’s particularities. The next step would be to achieve the complete automation, this means that the program will be able to find each image’s characteristic curve and calibrate wavelength and flux from the result. Once this is achieved, the results are represented through graphs to complete the program’s automation.

By having a system with these characteristics, it is possible to use the results in a spectrophotometric analysis in which Ha emission lines can be studied and Herbig-Haro objects can be identified (among other studies). Plate studies however, are not limited by a lack of handling experience anymore or by unavailable information. Through the validation of results and their comparison to traditional techniques a reliable system can be created.

A system with such characteristics makes possible to use its results in a spectrophotometric like analysis where Ha lines emission can be studied, some Herbig-Haro objects identification studies, among others. The ability to initiate studies in photographic plates is no longer limited by the lack of experience in its handling nor the availability of information. In order to have a trustable system, validation of results and its comparison with traditional techniques will be needed.

Regarding the images database, the staff of the laboratory has worked on the design and so on its programming. Currently, technicians of the lab are working on the digitizing of the astronomical plates -over 100 plates have been digitalized already-.

A prototype of the Astronomical Images Database of INAOE will be available soon.

Contact person: Raúl Mújica, Ph.D. rmujica@inaoep.mx