Bifocal anastigmatic telescope with five aspherical mirrors, comprising: - a first concave mirror, a second convex mirror, a third concave mirror and a first detector, which are common to a first and a second focal length of the telescope, - a first fourth mirror (M4 1) and a first fifth mirror (M5 1) that are associated with the first focal length, and a second fourth mirror (M4 2) and a second fifth mirror (M5 2) that are associated with the second focal length, the fourth and the fifth mirror associated with a focal length being retractable, so as to be positioned on an optical path of a beam corresponding to said associated focal length when the telescope is operating at said focal length, and outside of the optical path of a beam corresponding to the other focal length when the telescope is operating at the other focal length, - the first mirror and the second mirror being arranged so as to form, from an object at infinity, an intermediate image (lint) situated between the second mirror and the third mirror, - and for each focal length: * the third mirror as well as the fourth and the fifth mirror that are associated with said focal length being configured to form, from this intermediate image, a final image in a first focal plane (P F) of the telescope that is common to the two focal lengths and in which the first detector is positioned, * the fixed positions and forms of each mirror being determined from the generalized Korsch equations with 5 mirrors, with the constraint of the first, second and third mirror (M1, M2, M3) and of the first focal plane (P F) that are common to the two focal lengths, and so as to optimize the image quality in the first focal plane (P F) of the telescope in accordance with a predetermined criterion. - a first concave mirror, a second convex mirror, a third concave mirror and a first detector, which are common to a first and a second focal length of the telescope, - a first fourth mirror (M4 1) and a first fifth mirror (M5 1) that are associated with the first focal length, and a second fourth mirror (M4 2) and a second fifth mirror (M5 2) that are associated with the second focal length, - the first mirror and the second mirror being arranged so as to form, from an object at infinity, an intermediate image (lint) situated between the second mirror and the third mirror, - and for each focal length: * the third mirror as well as the fourth and the fifth mirror that are associated with said focal length being configured to form, from this intermediate image, a final image in a first focal plane (P F) of the telescope that is common to the two focal lengths and in which the first detector is positioned, * the fixed positions and forms of each mirror being determined from the generalized Korsch equations with 5 mirrors, with the constraint of the first, second and third mirror (M1, M2, M3) and of the first focal plane (P F) that are common to the two focal lengths, and so as to optimize the image quality in the first focal plane (P F) of the telescope in accordance with a predetermined criterion. * the third mirror as well as the fourth and the fifth mirror that are associated with said focal length being configured to form, from this intermediate image, a final image in a first focal plane (P F) of the telescope that is common to the two focal lengths and in which the first detector is positioned, * the fixed positions and forms of each mirror being determined from the generalized Korsch equations with 5 mirrors, with the constraint of the first, second and third mirror (M1, M2, M3) and of the first focal plane (P F) that are common to the two focal lengths, and so as to optimize the image quality in the first focal plane (P F) of the telescope in accordance with a predetermined criterion.