Galilean Telescope

In designing a Galilean telescope , the main points which should be kept under consideration, are :

1-A concave lens forms inverted and magnified image if the object for the concave lens is virtual and its distance is smaller than the twice of the magnitude of the focal length and grater or equal to the focal length.

2-The final image which is now going to be erect, should be at distance 25cm or greater I and it should be also virtual.

3- Where we require shorter telescope, Galilean is better option. Binoculars use this one.