ZWO ADC (Atmospheric Dispersion Corrector)

Atmospheric Dispersion Corrector or ADC, is a device that corrects the effects of Earth's atmosphere when taking a pictures of the Moon or a planet. In fact, in some cases when we record a planet image we can note a sort of chromatic aberration also in reflector telescopes (that has no lenses). This is caused by the effect of the Earth's atmospheric dispersion. The atmosphere basically acts as a prism, this effect changes depending on the elevation of the object above the horizon. The lower is, the greater the effect (that's why we advise to record images of planets and the Moon when they are over 15° above the horizon). ADC corrects this effect, which allows images objects, free from aberrations.

How ADC works:

When the light of a planet or the Moon passes through the Earth's atmosphere, it is "refracted" (deviated by an angle which depends on its wavelength). This effect, similar to that created by a prism, causes a significant change in the color known as chromatic aberration. This effect is very harmful to both visual and imaging. The ADC, or atmospheric dispersion corrector, is an opto-mechanical accessory which corrects this effect using the color superposition of two counter-rotating prisms. The ADC levers allow to move the rotator of the prisms and adjust the compensation. Below you see an image of Jupiter recorded with and without the ADC.

Technical data of the ADC:

- Material: H-K9L(Schott BK7)

- Surface accurancy: λ/10@632.8nm

- Deviation angle: 2°