AGEMA Super Doublet Apochromats



Our objective is a fluorite-doublet featuring a glass-in-front combination. Putting the glass in front protects the fluorite from any external influences. We use the highest quality optical materials for lens production, including glass that never undergoes secondary molding or annealing, and fluorite with optimal crystal orientation and uniform internal structure. Our complex lens cell eliminates the risk of deforming the optical components and protects them during telescope transportation. 


We use fluorite with unique dispersion properties in our design, resulting in an optical system with a high chromatic aberration correction. The amplitude of residual deviation in our system is 2.5–3 times smaller than the Abbe criterion for apochromatic lenses. The system’s Polychromatic Strehl Ratio exceeds 90% for the entire 430–700nm visual range. (Strehl Ratio graphs for each model are provided in the specifications.)

Here are the Strehl Ratio comparison graphs for a few known models of similar size with our AGEMA SD 130. All graphs were constructed for one focal plane with the main e line.

By carefully selecting our glass and fluorite and using the refractive index data from the actual glass melt, we produce optics precisely fabricated according to calculated design. Our improved polishing process provides higher quality surface and in combination with low light scattering of fluorite it delivers excellent contrast images.


Each lens is individually controlled during manufacturing and again at final assembly. All optical elements have Broad Band Anti-Reflection coating.


A Field Flattener, which improves the image quality in a larger field of view (a 60mm clear aperture ensures non-vignetting field for a 24mm x 36mm area/42mm diagonal) is also available. The Field Flattener is designed to guarantee diffraction quality over the entire field of view without disturbing color correction. 


The aluminum tube has internal baffles with knife edges that suppress indirect stray light. The tube is equipped with an extendable dew cap that reduces the entry of stray light and the chance of dew on the front lens. The inner surface is matte black; the exteriors are powder coated for a durable finish.


All our telescopes are equipped with a robust rotatable focuser (draw tube size depends on the model). The focuser has a 2-inch adapter with a collet-lock mechanism for attaching eyepieces, diagonal mirrors, prisms and other equipment. The Field Flattener can be installed by attaching it to the mating draw tube and securing it with the coupling nut.


The focuser has 125 mm of travel and dual-speed operation with an approximate ratio of 1:10. The backlash-free motion mechanism accomplishes a reliably smooth operation you can count on. Fixing the movable tube in any position is achieved with the drum-type brake conveniently located directly on the pinion shaft. This prevents damage to the rack if accidentally forced without releasing the brake. The focuser has all the necessary adjustments, including friction control that provides the ability to support different equipment weights. 

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