APO Refractor Telescopes with good color correcture

Very sharp telescopes for astronomy and astrophotography with apochromatic objectives.
There are almost as many Apos as there are stars in the sky, and the number is growing almost daily. We have therefore organized the Apos into categories.

ED Refractor: The 2-element objective has an ED element to reduce chromatic aberration, making it ideal for observing and getting started in astrophotography.

SD-APO: The 2-element objective has one or two high-quality special glasses, e.g. FPL53 and Lanthanum. The image is nearly color-free in focus. Ideally suited for observation. Photo correctors are available.

EDT-APO: The 3-element objective has a special glass, the chromatic aberration is significantly reduced. The apos are ideal for astrophotography, such as the TS PHOTOLINE series. Photo correctors and reducers are usually designed for telescopes.

High-End APO: The 3-element objective has 1-2 special glasses, such as FPL53, FPL55 or FCD100, e.g. the TS-CF Apos or the HIRO apos from Japan. These apos offer a pure color image and are also suitable for astrophotography.

Flatfield APO: These apos have a built-in image field corrector or are supplied with a corrector specially calculated and screwed on for the lens. They are specialists for astrophotography.