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400 mm F/13 telescope with built-in Atmospheric Dispersion Corrector

Submitter: Rik ter Horst
Description: In the coming years the observing conditions for most planets will be unfavorable(*). With elevations of only 15 -25 degrees above the southern horizon, the views will be severely affected by atmospheric dispersion, a prismatic effect caused by differential refraction of the atmosphere per wavelength.

For the BlackGEM/MeerLICHT telescope we built here in Dwingeloo, we've designed a corrector for this dispersion and I decided to integrate a similar solution in my new telescope, a 400 mm F/13 Modified Dall Kirkham. The system has a three-lens field corrector, of which one element is moved laterally in order to introduce dispersion opposite to the dispersion of the atmosphere. First tests show that it works flawlessly, and although the optics still need further correction I'm looking forward to observe these "low planets" in the next couple of years. I hope to show some first images soon!

(*) Due to the tilt of the Earth-axis with respect to the plane of the ecliptic (i.e. the plane in which the planets orbit the Sun), the declination of Mars will be negative this year, and even longer for the two Gas-Giants Jupiter and Saturn. Therefore, from our 52 degrees Northern latitude, Saturn and Mars will not rise more than 18 degrees above the southern horizon this year, and Jupiter will follow next year with comparable numbers.

Copyright: Rik ter Horst
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