This Takahashi FSQ-106EDX4 quadruplet is the ultimate portable no-compromise photo/visual refractor.
The Takahashi FSQ-106EDX4 quadruplet is a redesign of the FSQ-106, the workhorse of the Takahashi imaging refractor line. Its redesigned four-element double ED element modified Petzval optics have been optimized for imaging as well as visual applications. It is measurably the best no-compromise portable photo-visual refractor Takahashi has ever built, and they've built a lot of very good scopes over the years.
The FSQ-106ED is a 4.2" aperture f/5 (530mm focal length) four-lens photo/visual system using two ED (Extra-low Dispersion) glass elements. Based on the classic two-doublet Petzval design, the FSQ-106ED takes full advantage of the latest exotic glass types to produce levels of correction for coma, astigmatism, field curvature, secondary spectrum, spherical aberration, and spherochromatism that are unsurpassed - even better than their legendary fluorite scopes.
This Telescope's Optical System . . .
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Apochromatic modified Petzval refractor optical system: 4.2" aperture f/5 (530mm focal length) four-lens fully-multicoated system using two ED (Extra-low Dispersion) glass elements. The modified Petzval design uses a true apochromatic doublet objective lens with an ED element to gather the light. For most telescope manufacturers, this would be enough. But Takahashi goes a step further to perfect your observing and imaging experience. There is a second widely air-spaced ED doublet within the focuser drawtube itself. This second doublet optimizes the optical wavefront from the objective lens to eliminate any residual astigmatism. It also acts as a field flattener for wide field astrophotography. The result is a very wide and flat field with high contrast images that are without any hint of lateral color. Color correction has been extended to 1000nm, well into the infrared, to produce non-bloated photographic star images
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Large Image Circle: At prime focus the 88mm image circle covers a huge swathe of the sky measuring 9.5° in diameter. The large image circle will fully illuminate any 35mm, 645, or 6x7 medium format film camera; any vacuum back roll film holder; or any of the large format commercial grade CCD cameras available now or in the near future. Light fall-off is minor. The field is 90% illuminated at a 53mm diameter (a 35mm negative and the largest currently available SBIG Research Series chip measure only 44mm across their diagonals). It is still 67% illuminated at the edges of the 88mm image circle, an illumination that is easily compensated for with a CCD imager by a simple flat field.
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Long Back Focus: The generous back focus of 178mm allows the user to attach a variety of imaging packages, binoviewers, 2" star diagonals, and many other visual devices. The 178mm back focus has been designed to handle the ever-larger image trains of CCD imaging experts - electric focusers or temperature compensated focusers, flip mirror systems, filter wheels, adaptive optics systems, etc.
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Optional Focal Extender: If you need a slower system, an optional 1.6x 2" Extender-QE designed specifically for the new FSQ-106EDX4 converts the f/5 scope to a more high magnification-friendly f/8 system. It provides a 44mmm image circle with a 3° field of view.
This Telescope's Mechanical System . . .
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Compact Optical Tube: The all-aluminum 125mm diameter scope body is finished in ivory, with black trim, and is very solidly built. Knife-edge baffles within the tube block off-axis light for high contrast and dark sky backgrounds. The tube length of only 16.7" with the dew shield retracted allows the "Q" to be highly airline-transportable. Even when the dew shield is extended the total length is only 20.5".
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Focuser: The focuser is a new ultra-duty 4" rack-and-pinion design with both 2" and 1.25" eyepiece adapters. The focuser has a silky-smooth motion and oversize knobs that make it easy to achieve sharp focus, even at very high powers. The focuser includes a 10:1 ratio Micro Edge fine focuser for critical high magnification and photographic focusing.
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Camera angle adjuster: The focuser includes a new built-in camera angle adjuster/rotator that will carry a 5kg (11 lb.) load to handle the weight of the new large chip CCD cameras and their associated accessories.
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Dew shield: The optical tube has a retractable self-storing dew shield. A thumbscrew locks the dew shield in place, either when extended or when retracted. The dew shield serves the dual purpose of retarding the formation of dew during long observing sessions and improving the photo/visual contrast, much as a camera lens shade does.
