Aldo Radrizzani's Schmidt Archive

The astrophotographic work of Aldo revealed immadiately of great interest; he worked hard in the years between 1989 and 1998, producing an archive of 921 negative plates, most on Kodak Tecnical Pan 2415 (10x12 cm format, 4x5 in), cut to a diameter of 82 mm to be placed in the focal plane of the telescope. He imaged the sky for a total of about 20000 minutes (320 hours), all manually tracked at the reticle eyepiece of the guide refractor. The obtained images was of such a quality that his "traditional" astrophotografic work became of secondary importance: in example his images of the total eclipse, of Hale-Bopp, and of the Leonid shower, made with 24x36 mm and 6x6 cm reflex, was considered one of the best. And the Hale-Bopp was the only regret of Aldo, forced to image it with standard objectives or with friend's telescopes, because the trees at the East and West horizon inhibited the imaging with the Schmidt camera: we can only imagine the quality and the quantity of images he would have obtained!
The focal plane at the center of the telescope frames a huge 7° of sky, with a perfect optical quality all over the field, able to produce stars with a diameter of 10 µm (micrometers), near the limit of the Technical Pan 2415 film, with a grain size of 3 µm. This quality is obtained thanks to bending of the film plate, so that a perfect match with the curved focal plane of the Schmidt camera is obtained.
The plates are so big that to reproduce them on a 24x36 mm slide a reduction is necessary. Also printing them in big format, such as 70x70 cm, would not do justice to the originals, that would also sustain higher enlargements. This is the reason allowing to obtain tens of enlargement slides from a single plate, each with a galaxy, a nebula, a cluster and so on...

The huge work of scanning the image archive was started in 2005 by Lorenzo Comolli in spare time with a Canoscan 9950F. But scanning is only a little part of the work for building this website: first of all the scansions must be hand inspected at 100% resolution. Then each image is processed: gradients removals, levels and curves to extract any hidden information. This is a quite time consuming process, being the images really big (about 15000x15000 pixel, 16 bit/pixel, 400 MB). A complete excel spreadsheet was compiled from Aldo's hand written notes. Finally all the work was put online in this website. More info about this archive can be found in the article "Tutto il cielo di Aldo Radrizzani" ("All the sky of Aldo Radrizzani") published on the Italian magazine Nuovo Orione, March 2009.

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