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The FSQ-85ED is a 3.35” aperture f/5.3 (450mm 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-85ED 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 . . .

• Apochromatic modified Petzval refractor optical system: 3.35” aperture f/5.3 (450mm 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 buried deep within the telescope body. 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

• Large Image Circle: At prime focus the 44mm image circle covers a huge area of the sky measuring 5.6° in diameter, over 24 square degrees of sky. The large image circle will fully cover any 35mm negative or 35mm equivalent CCD chip (a 35mm negative and the largest currently available SBIG Research Series chip measure only 44mm across their diagonals). Light fall-off at the edges of the field is minor and easily compensated for in a CCD image by a simple flat field.

• Long Back Focus: The very generous back focus of 200mm allows the user to attach a variety of imaging packages, binoviewers, 2” star diagonals, and many other visual devices. The 200mm 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.

This Telescope’s Mechanical System . . .

• Compact Optical Tube: The all-aluminum 95mm diameter scope body is finished in ivory, with Takahashi green and black trim, and is very solidly built. The tube length of only 12.7” with the dew shield retracted and no visual accessories attached makes the “Baby Q” highly airline-transportable. The FSQ-85ED uses a special optional #85TH tube holder with offset plate designed specifically to mount this scope on an equatorial mount and balance it properly.

• Focuser: The focuser is an 80mm (3.15”) rack-and-pinion design whose drawtube terminates in a 2” eyepiece/accessory holder. A 1.25” compression ring eyepiece/star diagonal adapter fits into the extension tube to hold 1.25” accessories and is held in place by the extension tube’s thumbscrews. The scope should reach visual focus with most 2” star diagonals. Straight-through viewing and 1.25” diagonal use will require adding optional eyepiece extension tube #TET0002, at $69.95. The focuser has a silky-smooth motion and oversize knobs that make it easy to achieve sharp focus, even at very high powers. The right focuser knob has a smaller separate concentric knob that controls a 10:1 ratio Micro Edge fine focuser for critical high magnification and photographic focusing.

• Camera angle adjuster: The focuser includes a 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. The camera angle rotation is controlled by a large hand-tighten knob on the top of the focuser drawtube.

• Finderscope: No finderscope is supplied. There is a flat boss on the upper left side of the focuser that will accept an optional Takahashi finder bracket and finderscope. An optional 6 x 30mm Takahashi finderscope is shown in the feature images below.

• 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.