Astrophysics

Schmidt Camera Photographic Techniques

During the early 20th century, black and white photography flourished and the Schmidt Camera optical system was invented in the 30’s , this made it possible to develop a series of photographic emulsions that were deposited in glass plates, 20.3 x 20.3 cm in size. In arc degrees this means 5 x 5 arc degrees, thus obtaining in a single photographic plate a field equivalent to ten moons aligned in a single plate (width and length).

Several photographic techniques were developed with the Schmidt Camera and six optic filters were used along with an objective prism as a complementary optic in obtaining spectral images, among them:

• Single image without a filter in which a single exposition was achieved
• Three colors that consist of three expositions in a single plate (with one filter each): blue, yellow and ultraviolet, which allows us to determine a stellar field’s emission scale in three wavelengths.
• Six (or more) expositions technique, in a single plate in which the presence of variable stars -within nebular regions- can be determined.
• Spectral Plates: Obtained with an objective prism in the preceding edge, above the corrective lens, in this manner, sky fields are obtained through spectral images.

The following are in the category of plates with objective prisms:

• Spectral images without a filter: After obtaining one or several plates, comparison standards were analyzed in order to determine some emission or absorption lines, or spectral type, chemical composition and shifts, among other parameters and spectral studies.
• Spectral Plate with a F-29 Filter: Its wavelength is in the Balmer Series, H-Alfa, these images allowed us to determine the presence of stars in H-Alfa emission.
• Finding spectral plates with the Schmidt Camera.
• The Schmidt Camera has a third optical element that obtains spectral plates: the objective prism. It has a 65 cm. diameter, weighs 80 kg, has two flat sides (that meet in a 3.99 angle) mounted on an scale ring. When in use, this is lifted with a winch and placed according to the reference angle on the top part.
• Due to spectral images, astrophysicists are now able to analyze studied regions more closely.