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"I want to know why the universe exist, why there is something greater than nothing."

Steven Hawking

Scientist, Space Lover

Dusk of the Planets

Tomorrow's picture: More than 1000 Words (Usually) < | Archive | Index | Search | Calendar | Glossary | Education | About APOD | > Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.

21st Century Wet Collodion Moon

In the mid 19th century, one of the first photographic technologies used to record the lunar surface was the wet-plate collodion process, notably employed by British astronomer Warren De la Rue. To capture an image, a thick, transparent mixture was used to coat a glass plate, sensitized with silver nitrate, exposed at the telescope, and then developed to create a negative image on the plate. To maintain photographic sensitivity, the entire process, from coating to exposure to developing, had to be completed before the plate dried, in a span of about 10 to 15 minutes. This modern version of a wet-plate collodion image celebrates lunar photography's early days, reproducing the process using modern chemicals to coat a glass plate from a 21st century hardware store. Captured last November 28 with an 8x10 view camera and backyard telescope, it faithfully records large craters, bright rays, and dark, smooth mare of the waxing gibbous Moon. Subsequently digitized, the image on the plate was 8.5 centimeters in diameter and exposed while tracking for 2 minutes. The wet plate's effective photographic sensitivity was about ISO 1. In your smart phone, the camera sensor probably has a photographic sensitivity range of ISO 100 to 6400 (and needs to be kept dry ...).

Infrared Helix

Over six hundred light years from Earth, in the constellation Aquarius, a sun-like star is dying. Its last few thousand years have produced the Helix Nebula (NGC 7293), a well studied and nearby example of a Planetary Nebula, typical of this final phase of stellar evolution. Emission in this infrared Spitzer Space Telescope image of the Helix comes mostly from the nebula's molecular hydrogen gas. The gas appears to be clumpy, forming thousands of comet-shaped knots each spanning about twice the size of our solar system. Bluer, more energetic radiation is seen to come from the heads with redder emission from the tails, suggesting that they are more shielded from the central star's winds and intense ultraviolet radiation. The nebula itself is about 2.5 light-years across. The Sun is expected to go through its own Planetary Nebula phase ... in another 5 billion years.



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