Did you know that most telescopes work well for daytime viewing in addition to astronomy? If your telescope is refractor or cadioptic (Schmidt-Cassegrain is the most popular example) and you would like to use it to view terrestrial objects, the most useful accessory you can get is a turning prism.
If you look through a telescope with an ordinary mirror or star angle prism, you will notice that the objects are either upside down, mirror images or both. This is not a problem when observing the stars, but it can interfere with observing terrestrial objects, especially tracking moving objects such as birds or boats. Fortunately, this problem is easily solved. By installing a Celestron 45º pivoting prism in the telescope's focus tube in place of a standard angle mirror, and placing the eyepiece in the pivoting prism, the objects turn correctly on both axes. The 45º angle of the Amici prism is very pleasant for daytime observation, when the telescope is mostly in a horizontal position.
Note: Installing a turning prism in a Newton-type mirror telescope does not correct the angle of the image to normal. The optical structure of the Newton telescope always produces an image that is rotationally indirect. This does not mean that a Newton-type mirror telescope cannot be used for daytime observation, but it requires getting used to when the position of the objects is unrealistic.
