Re: finding telescope mirror size

Hi Kevin.

I think that you are confusing two different concepts about telescopes, resolving power and seeing. Almost any telescope will allow you to see great distances. With the unaided eye on a very dark night at this time of year it is possible to see the Andromeda Galaxy which is almost 3 million light years away. Seeing distance is no problem with a telescope or with binoculars. Mirror size is important for two reasons. First, it allows us to gather more light from faint objects so we get better definition. Second, a larger mirror allows us to separate two objects that are close together. This is the resolving power of the mirror. If there are two stars that are close together, either optically or gravitationally, then the larger the mirror, the farther apart they will appear. The resolving power of a telescope is dependent on the wavelength of the light and size of the mirror or lens.

The equation is (the angle of separation) equals 1.22 times the wavelength divided by the diameter of the lens. Angle=1.22(wavelength)/Diameter of mirror There are physical limits to these values due to diffraction and atmospheric conditions. We are building larger and larger telescopes and place telescopes outside our atmosphere, so we are able to get finer and finer detail from those instruments. This allows us to resolve smaller objects at a greater distance.

I hope that this answers your question.