Artifacts in the SDSS

What is That?

No telescope or data processing system is perfect; sometimes, meteors or satellites come into the telescope’s field of view. The pictures below show a few of these “artifacts” – mistakes and surprises in the data. It’s up to you to become familiar with these artifacts because the Navigation tool does not label them for you. To learn more about how the SDSS collects and processes data, see the Preflight trainings under Capturing and Recording Light.

Each star, however bright, is still point-like. They only appear to be extended, with a `halo’ because of the scattered light inside the telescope. The vertical and horizontal faint stripes are due to the `bleeding’ of charge inside the detector.

Here is a second example of how bright stars appear in the SDSS. On the raw images these were much stronger, but our software successfully removes most of this effect.

 

Each bright star appears as a tilted ‘cross’ on the image. This pattern is called a ‘diffraction spike’, and is due to light scattered on the four beams that hold the secondary mirror of the telescope in place.

A wobbling satellite on a low-earth orbit. The varying intensity of the light is due to the rotation of the satellite. It has crossed the telescope field in a very short time, and it is red because its path fell on the detector with the red filter, not that the satellite is red itself.

 

Bright meteor captured in the act of burning up in the earth’s atmosphere. The trail is colored green because the image of the meteor was captured in only one of the 5 SDSS filters.

A wobbling satellite on a low-earth orbit. The varying intensity of the light is due to the rotation of the satellite.

 

The blue ‘ghost’ is the result of light from a nearby very bright star reflected inside the telescope. It is blue, because it was reflected onto the detector with the blue filter.

The red ‘ghost’ is the result of light from a nearby very bright star reflected inside the telescope. Even though such reflections are quite weak, for very bright sources they still cause such artifacts to be detected.