When placed into a conventional achromatic refractor, chromacor removes most of the false color (chromatic aberration), and corrects spherical aberration as well. This device was developed by Valery Deryuzhin of Aries (Ukraine).

Chromacor works better with several Chinese refractors made by Synta. These refractors vary a lot as far as optical quality is concerned and are known as "Celestron", "Bresser", "Konus", "Skywatcher", "Astroview".

The Chromacor corrects for chromatic aberration, spherical aberration and spherochromatism. If a telescope has an excellent correction and its spherical aberration is insignificant, then a Chromacor-N is a right choice. The Chromacor-N corrects for chromatic aberration and spherochromatism only, without any effect spherical aberration. If a telescope has significant amounts of spherical aberration, then choose from four other types of Chromacors. These four Chromacor types O1, O2, U1, U2, correct for different amounts of spherical aberrations in the objective lens.

The following list summarizes the five Chromacor types.

  • Chromacor-O1 has 1/6 - 1/7 wave overcorrection built-in.
  • Chromacor-O2 has 1/3.5 - 1/4 wave overcorrection built-in (under development)
  • Chromacor-U1 has 1/6 - 1/7 wave undercorrection built-in
  • Chromacor-U2 has 1/3.5 - 1/4 wave undercorrection built-in
  • Chromacor-N has Null spherical correction, spherical aberration remains unchanged.

Uncorrected image (left), corrected image (right)

Click on images for full-sized view.

Comparison images (Synta 150 mm F/8 with matched chromacor). Daylight images.

Comparison images (Synta 150 mm F/8 with matched chromacor). Moon.

Comparison images (Synta 150 mm F/8 with matched chromacor). Vega.

Chromacor is very sensitive to both alignment and centering. The focuser has to be properly centered and aligned using a cheshire eyepiece (see below).

Synta (Sky-Watcher) 150 mm F/8 with matched Chromacor. Installation of a new Crayford focuser.
  • Crayford focuser
  • Replacing the old focuser

  • Collimating the Crayford focuser (Cheshire eyepiece)

  • Crayford focuser + Nagler 20 mm Type II

  • Crayford focuser + FujiFilm S1 Pro
  • Synta (Sky-Watcher) 150 mm F/8 with matched Chromacor
  • Synta (Sky-Watcher) 150 mm F/8 with matched Chromacor

  • Chromacor (observation setup)

  • Chromacor (imaging setup). FujiFilm S1 Pro digital camera