Description and Design Goals

Introducing the 110mm F6 Starfire GTX dual-purpose portable refractor. The design goal was three-fold: 1) a compact refractor with as much aperture as possible that would fit into an airline overhead case, 2) a fast, highly-corrected triplet refractor that can cover a full format CMOS chip with pinpoint stars to the corners when coupled to our matching Telecompressor-Corrector,   3) a superb visual refractor with the highest possible polychromatic Strehl in a compact triplet lens.

Airline Transport.  The 110GTX fits nicely into an airline-approved carry-on case with plenty of padding for protection.

Optical Design for Newest Small Pixel Cameras.  We chose a focal ratio of F6 for the objective lens and an aperture of 110mm as a sweet spot for portability and deep-sky imaging capability. The lens uses the newest Super-ED glass available from our Japanese optical supplier along with two matched elements to provide diffraction-limited performance from deep red to deep violet. The scope is designed for imaging with our F5 TCC, and will cover the full-frame 35mm format of the popular CMOS cameras. The F5 focal ratio produces a maximum 5-degree, 50mm image circle that is matched to the resolution capabilities of the 3.75 micron pixel size. The TCC is designed to extend the color correction range far beyond the visual spectrum to produce high-resolution images from the latest CMOS sensors. Polychromatic spot size is well within the Airy disc limit, even at the periphery of a full 35mm format.  Refer to the Technical Design Details tab to see the spot diagram. 

Visual Performance.  For the best possible visual performance, we designed the objective lens to have very high polychromatic Strehl ratio over the visual spectrum for wavelengths of red, yellow, green and blue colors. We chose the wavelength range that was matched specifically to the human eye response for best contrast and resolution at any power - whether it be low-power, wide-field scanning of the Milky Way or high-power observation of the Sun, Moon, planets and double stars. Furthermore, the lens was designed for best wavefront performance, not for RMS spot radius. The reason for designing the lens this way is to provide the highest contrast over the largest possible wavelength range. In that way, the lens performs extremely well with high-power eyepieces, identical to what much longer focal ratio lenses of this aperture would produce. Even so, the polychromatic spot radius stays well below the Airy disc limit for all visual wavelengths and over a field of almost 1 degree or 2 full Moon diameters without adding any extra optics (field flatteners) to the optical train.

To achieve these high corrections, we used carefully-selected optical glass for the outer mating elements that surround the central Super-ED glass. This glass is the perfect material to produce a fast high-Strehl objective. Normally, to get this level of color correction at such a fast focal ratio requires either wide airspaces between the elements, or putting the sensitive ED glass up front where it can be damaged by overzealous cleaning.

Wide airspaces cause two problems that we want to avoid - one is sensitivity to decentering and the second is long cooldown time.  With close-spaced elements and the expensive ED element safely snuggled between two hard mating-elements, the scope is very rugged and impervious to rough handling. The multi-layer coatings are applied with ion-beam assist techniques, and therefore are almost as hard as the underlying glass.  The entire lens cell can be easily slid out of the scope's main tube by removing 3 screws. This allows easy cleaning of the rear surface in case of excessive dew or dust settling on this surface.

FEATURES

• 3.5" Astro-Physics focuser - silky smooth with a greaseless drawtube and the dual-speed mechanism of the 9:1 Micro. The dual-speed feature is particularly advantageous for critically focusing this fast focal ratio. A digital focusing system will be available for imaging.
• Compact, lightweight tube assembly that fits into your carry-on luggage. Fully retractable felt-lined dew shield slides to its fully-extended position with thumbscrew to secure it in place.
• Latest multi-coating technology will provide optimum light transmission.
• The 110mm StarFire GTX will fit into a case for airline transport.
• Optional Telecompressor-Corrector (110TCC) converts the 110mmF6 to a fast 550 mm focal length, f/5 imaging machine with pinpoint stars across the field.
• Optional 3.5" Prime Focus Field Flattener (110FF) converts the 110mmF6 to a 732 mm focal length, f/6.65 imaging machine with pinpoint stars across the field.