M13
The globular cluster M13 is one of the most famous star clusters. Under good observation conditions, it can be seen as a nebulous cloud with the naked eye. It was discovered by Edmond Halley as early as 1714, and Charles Messier included it in his catalog under the number M13 on June 1, 1764. The cluster is more than 7.7 kpc away and is estimated to be 12 billion years old. It is made up of approximately 100,000 stars. The concentration of stars rises towards the center and is estimated to be about 500 times higher there than at the edge. The cluster also contains blue wandering stars, the origin of which is not yet fully understood. In 1974, M13 became the target of a radio message sent from the newly built radio telescope in Arecibo. Also prominent in the image is the galaxy NGC 6207.
This is one of the first tests of the new astrograph. A small shadow caused by the primary mirror mounts can be seen in the diffracted rays from the brighter stars. The aperture to remove this minor optical defect was already in production at the time of image processing.
