The Sloan Digital Sky Survey is the name given to a very large collection of images taken with a special telescope that is located at Apache Point New Mexico.


Like most modern telescopes that are used for research, the SDSS telescope uses a large curved mirror to gather light. This is called the primary mirror.


The curve of the primary mirror reflects the light toward a second mirror. This secondary mirror is smaller and is located in front of the primary mirror. It directs light through a hole in the middle of the primary mirror through two lenses that help focus the light more and then to the camera.


The job of the SDSS telescope is to take images of very dim objects over big portions of the sky. To do this, engineers had to design the telescope that is very steady and is able to capture and focus a lot of light. Let’s see how they did it.

Galaxies outside our own Milky Way Galaxy are one of the main targets for the SDSS. Galaxies are collections of billions of stars. They are so faint and far away that only a few can be seen without a telescope. The SDSS telescope has captured images of over 200 million galaxies. To capture enough light to record these galaxies engineers designed the telescope with the mirror that is 2.5 meters across.


Another goal of the SDSS is to see where the galaxies are located in the sky. To take images of large parts of the sky at a time, engineers designed the telescope with a field of view that is the size of 30 full moons! This is very big compared to most research telescopes.


Engineers did many things to ensure that the telescope will not move when it is taking pictures. Any movement of the telescope makes the images blurry. One thing they did was to surround the telescope with wind baffles that help keep the air around the mirrors very steady.


The images that are recorded by the SDSS camera are stored on computers. Scientists measure many things about each of the objects such as their size, brightness and color.


The images and information that goes with the images is stored on tables on computers so that they are easy to search. This storage system is called a database.


The SDSS database is what we will use in all the Voyages activities to learn about the universe.


Good Luck and Have Fun.