The invention relates to an adapter (1) for securing a camera (2) or an optical measuring device onto a telescope (3). The adapter (1) comprises a platform (6) for securing the camera (2) and a cylindrical sleeve (4) for securing onto an eyepiece (16) of the telescope (3), wherein the sleeve (4) is attached by flange onto a base plate (5) extending at right angles to a sleeve axis (7). On the base plate (5) a guide is formed, which is formed by two guiding tracks (9, 10) and runs at right angles to the sleeve axis (7), wherein the platform (6) can be adjusted by said guide. On the platform (6) a mechanical stage (23) is also arranged by means of which the camera (2) can be adjusted in a plane running parallel to the sleeve axis (7).