A filter that removes the need to combine the Neodymium Moon and Skyglow filter with the Fringe Killers to deliver an amazing colour-corrected image to achromatic refractors. The Baader Semi-Apo does it all in one filter.
Baader Semi Apo Filter against violet fringes of refractors - 1.25" cell
By selectively filtering out of those parts of the spectrum where the false colour of achromatic refractors is significant, this disturbing effect is reduced. Contrast and image definition are improved. In addition, neodymium-containing glass provides a more neutral colour tone.
This filter delivers a dramatic improvement on sharpness and contrast, even with smaller aperture refractors. The RGB enhancement of the Neodymium substrate layer boosts colour contrasts, for planetary viewing and particularly for Jupiter and Mars.
Differences to Fringe Killer and Contrast Booster:
These two filters have a similar effect. They both reduce false colour, but the image also gets a yellowish touch. In some cases, for example for planetary observation, this is wanted.
The Semi Apo filter causes significantly less yellow tinting. The image has only a slightly warmer touch with a light yellow-green tone. It also has more transmission compared with a standard minus violet filter. It can also be used for deep-sky and double star observation.
The Semi Apo filter is a good addition to the Fringe Killer and the Contrast Booster. It can replace a normal minus violet filter and gives less colour shift.
