A coronagraph is a telescope that can see things very close to the Sun. It uses a disk to block the Sun's bright surface, revealing the faint solar corona, stars, planets and sungrazing comets. In other words, a coronagraph produces an artificial solar eclipse.

The Solar and Heliospheric Observatory (SOHO) has two coronagraphs onboard, one with a 3-degree field of view (the "C2" coronagraph) and another with a 16-degree field of view (the "C3" coronagraph). For comparison, the Sun itself is 0.5 degrees across. C2 coronagraph images are usually colored red; C3 coronagraph images are blue:

Related links:

• the latest coronagraph images from SOHO
• A Christmas Star for SOHO -- (Science@NASA) On May 17th, 2000, SOHO coronagraphs recorded an impressive conjunction of Venus and Jupiter that happened near the Sun
• Some Comets Like it Hot -- (Science@NASA) Using SOHO coronagraphs, amateur astronomers are discovering pieces of a giant comet that broke apart in antiquity as the fragments zoom perilously close to the Sun.
• Solar Smoke Rings -- (Science@NASA) The Sun puts on a dynamic show with a series of swirling coronal mass ejections
• Kamikaze Comets -- (Science@NASA) Many sungrazing comets discovered by SOHO appear to have come from the breakup of a single gigantic comet more than 2000 years ago.