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Questar QM 200 Long Distance Microscope
(Pictured above is the QM 200 Long Distance Microscope with it's 90 Degree Port, Questar Positioning Stage with Camera Cradle)

The Questar QM 200 is the largest Long Distance Microscope in our product line. This instrument approaches the resolution of the QM100 with a limit of 1.25 microns at 30.5cm (12 inches) and yet, it can achieve this performance at twice the working distance of the QM100. Furthermore its standard diffraction limited field of view is 16mm, with 25mm attainable with the Barlow lens. And so it is best suited for applications where the demands of relative aperture and resolution wit field of view are made and closer working distances are impractical. The QM-200 is the winner of the "Photonics Magazine" Circle of Excellence Award for 1989.

For applications requiring very high magnification and resolution, and which will allow the user to work from distances of 30.5cm (12 inches) to 76 cm (30 inches), the QM 200 is unrivaled in performance and flexibility.


Optical Characteristics:

  • Design: Maksutov-Cassegrain Catadioptric
  • Standard Corrector Lens: BK7, MgF2 AR Coated; multilayer dielectric coatings optional
  • Optional Corrector Lens: Fused Silica (for enhanced UV spectral response), MgF2 AR Coated
  • Primary Mirror: Pyrex substrate, aluminum coated with SiO overcoat; Zerodur substrate optional
  • Corrector Lens Clear Diameter: 140mm (5.5 inches)
  • Primary Mirror Diameter: 222mm (8.75 inches)
  • Standard Secondary Mirror: aluminum coated with SiO overcoat; silver with ThF4 overcoat optional
  • Secondary Mirror Diameter: 28mm (1.1 inches)
  • Baffling: Helix in central tube, all interior surfaces black anti-reflection coated

Mechanical Characteristics:

  • Barrel Material: Aluminum hollow bar, machined from seamless stock
  • Barrel Length: 80cm (22.29 inches)
  • 90 Degree Port: Machined aluminum, corrosion resistant; selectable axial or 90 degree Port.
  • Tube Assembly Length: 56.6cm (12.11 inches) front cell to focus knob seat
  • Tube Assembly Diameter: 23.4cm (9.20 inches) maximum overall
  • Tube Assembly Height: 25.7cm (10.1 inches) base of mount to top of barrel
  • Tube Assembly Weight: 14.1 kg (31 pounds)
  • Mount: Machined aluminum, 1/4"-0, 3/8"-0, and 3/8"-16 mounting holes
  • Focus Mechanism: Internal. Ball slide bearing thimble, moves on stainless steel (s.s.) baffle tube (centerless ground) lead screw mirror transit drive,
    motorized with variable speed remote control of focus and of precision focus stage
  • Finish: Aluminum components anodized natural, dark blue, or black
  • Carrying Case: ATA, Furnished Standard


  • Focus Range: 30cm (12 inches) to 76cm (30 inches)
  • Back Focus: 70cm (2.75 inches) minimum, 11.4cm (4.5 inches) nominal, 15.2cm (6 inches) maximum
  • Optical Resolution: 1.25 microns at 30cm (12 inches)
  • Format: Diffraction Limited Field 16mm diameter; with Barlow 25mm
  • Standard spectral response: 330nm to 2.3 microns, optional systems with wider spectral response available.
  • Optional spectral response: 200nm to 3.5 microns.

Object Distance Numerical Aperture f/No.
76cm (30 inches) 0.076 6.6
61cm (24 inches) 0.096 5.2
46cm (18 inches) 0.115 4.3
30cm (12 inches) 0.131 3.8


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