When you demand performance you take the best.

Questar produces some of the world's most powerful long focal length surveillance lenses. The same optics that go into our surveillance products go into our space qualified telescopes, selected above all others for their superb images and ruggedness. No other application can ask more of a lens, and in no other application can seeing be more important - Experience counts.

Questar has been a leader of the long range surveillance market for more than thirty years. When images of the earth taken through a Questar from the Gemini spacecraft were reported in Newsweek Magazine in 1965, it was news because it was the beginning of surveillance photography from space. When Apollo astronauts reported seeing a twelve and a half foot object from 1000 miles through a Questar, it was on the front page of the New York Times.surveillence-1 In 1985 a highjacker in Beirut was identified from two kilometres, and in 1986 a Questar was used to identify the cargo being unloaded off a freighter in Nicaragua from twenty five kilometres. When video evidence of a SCUD missile launcher in Kuwait was presented to the UN for sanction of Desert Storm, a Questar SZ 180 was used to make the images from a distance of thirty kilometres.

What this experience means to you is that Questar can provide an integrated system that is optimised to perform how and where you need it to perform. Questar integrates their lenses with the best of electro-optics, tripods, motion control, packaging and environmental protection. An entire system may need to fit into a small case, including lens, tripod, camera, monitor and recorder. Or the requirement may be for a permanently installed day/night system with remote operation of lens functions, pan and tilt and camera selection, with complete remote control over image contrast and enhancement. Questar's experience takes the guesswork out of your problem solving.

An example of aerial surveillance from l kilometre with a Questar3.5.


ORBIT VIEW: This Cape Kennedy photo taken from Gemini 5 is clear enough to show causeway and 33-foot.wide bridge (upper right)-and the potential of satellite espionage.

The fast telescopic images of earth were reported in Newsweek Magazine in September 1965.

Looking Sharp
A Questar telescope is one of the finest pieces of optical equipment made. It has a focal length of 56 inches but a system of mirrors allows the light beam to be neatly folded into a barrel only 8 inches long. Attached to a camera for picture-taking purposes, it is theoretically capable of photographing an object as small as a motorcycle from 100 miles away.

A real test of a lens is to increase the focal length until it no longer makes useful images.

The exacting optical tolerances that Queslar guarantees, contribute to both resolution and the versatility of the lenses. There are times when extended focal lengths are required to do the job.


The features offered by Questar lenses have made them the choice for police, intelligence and military users in more than thirty countries, and by more than two hundred Federal and State agencies in the United States.

Resolution: Take a look at these pictures. Any lens can be designed to have a long focal length. Only the world's best will make pictures like these. Our optics are hand-figured, something you will never find in a mass produced video lens. Our lenses are tested and guaranteed to give you diffraction-limited performance, which means that the only limitation on what you are seeing is the air and the physics of light.

Ruggedness: Our Maksutov Cassegrain optical design has only two main elements which are permanently collimated. Our Multi Focal Length and Step Zoom series lenses are sealed at all mating surfaces and are provided with optical windows to protect them from moisture and dirt.

Compactness: One of the remarkable things about Questar surveillance lenses is their size. More than three meters of focal length fit in a thirty five centimetre package weighing six kilograms. Almost five metres fit in a sixty centimetre package, weighing only eighteen kilograms, fully motorised.

Versatility: A Questar user at U.S. Army Special Forces called the Questar lens the most useful lens he carried. No other lens has the spread of focal lengths provided by Questar. A single lens gives wide surveillance views, and still has the power to move in for critical evidence. A single lens operates under both day and night illumination.

Sensitivity to JR: Video has transformed the business of surveillance, providing features like real-time display, still frame and tape documentation, image enhancement, and transmission by phone line and microwave. But you have to give video cameras and image intensifiers the right kind of light. Multi-element zoom lenses absorb light at every surface. It is just the light your camera wants to see. Questar uses a mixture of mirrors and a minimum number of lenses, optimising the amount and wavelength of light that gets to your camera and night vision equipment.

Here, the top photo was taken with a 55mm lens from a distance of 3.5 kilometres, the lower two photographs were taken front the same location through the Questar Field Rangers 3.5 and at 9000mm and 18000mm focal lengths respectively. Although atmospheric conditions often make photography at these focal lengths very difficult, the photos demonstrate that Questar lenses will make images at high magnifications.

We take the danger out of getting close

These video images demonstrate performance that can be expected under different light conditions. All were shot on the same day, and no attempt was made to wait for perfect weather or pictures. Air turbulence was moderate with brief periods of stability.

Here, the images in the left column were taken . with a 20mm f/1.6 lens. The images on the right were made with the SZ 180 at various focal lengths.


During the day, even when overcast, the S'7, 180 easily has the capacity to read a license plate at 2.5 kilometres at an EFL (effective focal length) of 4800mm. Finding a target at this distance would he very difficult at fixed focal length, but the 8-to-1 range of focal lengths performs the task quickly and easily.

At dusk with a significantly longer range of 9 kilometres, the effects of turbulence are more pronounced, however, the essential information is clear in this image. In spite of the lower light levels, even at a 4800mm focal length the Questar maintains high contrast.

Urban situations at night present low light level conditions with bright spot sources of light which tend to obscure the surrounding detail. Superb baffling and absence of light scatter in the lens maintain detail in this image shot at a range of 3 kilometres at a 2400mm focal length.

In the cover shot for this image the faint centre line of the road is barely visible under a 1/8 moon with heavy mist and no other ambient light. A person was no longer detectable to the eye at about 40 metres. Using image intensification and integration to increase sensitivity, detection is easily accomplished at one kilometre. This 1800mm EFL image took several seconds to make.


Questar surveillance lenses are day/night capable instruments with the highest resolution and focal length available in their aperture. They are available in two apertures: 90mm and 180mm, three configurations. Each is equipped to provide variable focal length performance with any video camera. The 3.5 provides focal lengths of 480mm to 3100mm, the Seven allows focal lengths of 635mm to 4800mm.


Field Ranger

The Field Ranger 3.5 and Seven are Questar's, most compact configurations. They are provided with accessories for varying focal lengths and filters without removing the camera.

Field Model spec Sheet 2017



Questar Field Ranger 3.5

The Questar Field Model is the ultimate spotting scope. From 10 feet to Infinity, for situations requiring long focal lengths, no other scope matches the Field Model's resolution and image contrast. As a telephoto lens, the Field Model is comparable in size to a 250mm f/2.8 lens, and weighs less than 3 pounds. It has all the controls of the Standard 3.5, giving the observer 3 powers per eyepiece and giving the photographer a separate selectable port for the camera attachment.

See detail PDF.



The Questar Birder is the spotting scope everyone turns to when identification hangs in the balance.
Spotting Scope
Standard powers of 8.5x, 40x and 65x resolve details that are feather-edge fine at 20 feet or 2000 feet. Optional available eyepieces can vary this to increase powers. The built-in multi port control box allows for visual & for photography. Our 89mm aperture and long 1300mm focal length provide light grasp and the power to reach out beyond the limits of other scopes.

See detail PDF.



Step Zoom


The SZ 90 and SZ 180 are completely motorised lenses with microprocessor control. They share the weatherisation and optical characteristics of the MFL, but have unique features provided by the microprocessor. All functions are controlled with a hand-held terminal with soft keypad. Lens function status is reported in a LCD window. Both motor speed and acceleration are programmable, and the lens refocuses automatically with each focal length change. A serial communications port is provided for computer control.



The MFL 3.5 and Seven provide the convenience of internally mounted auxiliary optics and filters, and are weatherised with seals at all mating surfaces and sealed optical flats to protect the lens. Five focal length changes and selection of four filter positions are activated from knobs mounted on the back plate of the instrument. Focal length and filter status is indicated by LEDs.


Through many years of experience in surveillance Questar has developed a line of accessories for the specialised needs of the surveillance customer, suited to the requirements of long focal length lenses.SZ-90-remote

Automatic Light Control: The ALC module contains a pair of continuously variable chrome coated neutral density filters that can be manually controlled, or auto-matically driven by the video signal. It optimises contrast in the image under varying light conditions.

Tripods: The selection of a proper support for a lens is essential. Questar offers several options of varying sizes, equipped with features such as fluid pan heads and telescoping legs to make the use and transportation of long focal length lenses comfortable and effective.

Shown is remotely operable day/night system. Included is the SZ, 90 with integrated Automatic Light Control. Alt/ Azimuth on Heavy Duty Pier with joystick control and position readout. Remote video control includes an analog processor for CCD camera and controller image intensifier.

Alt/Azimuth Mount: Most pan and tilt mechanisms offer far too little angular resolution and sufficiently slow slewing speeds to be used at focal lengths of several metres. Questar have developed two sizes of a motorised alt/az mount that provide both the required resolution and dynamic range to make positioning a long focal length lens very easy. They are equipped with joystick or computer control and are available with encoders and display of position feedback.sealed-pressurised

Video: Questar uses instrumentation grade video with their lenses. Characteristics such as signal to noise and MTF are just as important as number of television lines to create high contrast, high resolution images. Monitors are available either desk top or rack-mounted, integrated into a carrying case with a VCR, AC/DC compatible. Several types of image intensifier are available to suit various requirements.

For permanent installations, a sealed pressurised system may be provided as in this system for border surveillance which includes two cameras and electronics for remote operation. The large alt/azimuth mount is also weatherproof.

Image Processing: Both analog and digital image processing greatly improve image characteristics. Analog processing increases contrast under every condition, and digital processing greatly increases sensitivity and reduces characteristic noise under very low light level conditions.

Specialised Components: Specialised features such as remote switching of cameras, still frame image capture and storage, and remote operation and transmission of images are available.

Environmental Enclosures: Hermetically sealed, pressurised enclosures with features such as a sun shutter and motorised lens cap may be custom designed to satisfy the requirements of specific applications.

Packaging: Questar packages their lenses and accessories in either soft or hard cases. Accessories are carefully packaged for accessibility or may be integrated into the case for convenience in the field.