FAQ's

This page provides answers to the most frequently asked questions in the area of rifle scope technology, reflection sights, binoculars and lighting technology.

Rifle Scope Technology

How does the tipcontrol in DOCTERunipoint work?

The reticle illumination of the DOCTERunipoint is solely controlled by pressing the red button on the dome of the illumination unit (pressing the owl). The device is switched on or off via double-click, similar to a computer mouse. In doing so it is important to observe a certain time frame. If the interval between the two clicks is too long, the electronics will not respond and the illumination cannot be switched on or off. This functioning principle prevents an unintended switch-on of the rifle scope for example when inserting it into the sheath.

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What happens to the reticle if the zoom level is changed?

The behaviour of the reticle when changing the zoom level is determined by its position inside the rifle scope. A rifle scope has 2 image planes. If the reticle is located in the first image plane, it will also be magnified when changing the zoom level. The proportion (overlap measure) of the reticle to the target always remains the same. This enables the estimation of the distance of the target by means of a known bar distance of the reticle in all zoom levels. If the reticle is located in the second image plane, the size of the reticle does not change. Therefore, the overlap measures of the reticle change when adjusting the zoom level. Here, it is almost impossible to estimate the distance. However, this option allows a clean shot, even for larger distances, because the reticle covers very little of the target. The DOCTERunipoint with the reticle 4-0 combines both options in one rifle scope. The magnifying reticle 4 (first image plane) allows the estimation of distances and the reticle in the second image plane enables as little covering of the target as possible.

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What is the difference between an illuminated daylight reticle and an illuminated twilight reticle?

Until the beginning of the 90’s, rifle scopes were only available without illumination. After the agreement was reached that an illuminated reticle poses no violation of the German Federal Hunting Act, rifle scopes with an illuminated reticle were virtually booming and today, they are the standard in the field of hunting.

Another standard feature is the possibility to regulate the brightness of an illuminated reticle. For the twilight reticle, this adjustable brightness is adapted to the perception of the eye at night. Hence, overexposure of the target and an overstimulation of the eyes is prevented. In most cases, the reticle 4 is the basis. If used during the day, shooting is effected as normal via reticle 4 without activating the illumination. Here, the illuminated twilight reticles “light spot” or “light cross” are available for the DOCTERclassic.

Due to the development in the area of diode technology, it is nowadays also possible to offer rifle scopes with an illuminated daylight reticle. As the name suggests, this illuminating option is intended for use during the day. Thanks to the high performance of the modern diodes, the reticle can be displayed at almost all lighting conditions. Therefore, DOCTERunipoint is the ideal companion for hunting during winter, from the sun shining on the snow to raised hide hunting at night – thanks to their dimmable illuminated daylight reticle. It goes without saying that the brightness control is also adjusted to the natural perception of the eye.

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How long is the battery life?

The life of a battery, regardless of the type, mainly depends on the frequency of use and environmental influences. In doing so, the ambient temperature plays an important role. The type of the illuminated reticle is another key factor for the durability of the battery. Thus, illuminated daylight reticles require more power than illuminated twilight reticles, due to the increased brightness. If rifle scopes are often used at cold temperatures, the voltage of the battery will decrease quickly. It is recommended to replace the battery at the beginning of the hunting season, just to be on the safe side. A spare battery which is carried inside the warm trouser pocket also helps to avoid unpleasant surprises during the wintry drive hunt.

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What happens if I wear spectacles in combination with a rifle scope?

People who wear spectacles are always at a disadvantage compared to people who do not wear spectacles. Due to the use of additional lenses (spectacle lenses), image defects might occur which give the observer an altered visual impression and which are possibly deemed to be disturbing.

Each rifle scope is equipped with a dioptre compensation which is able to compensate the ametropia of a shooter up to a certain degree. However, people who wear spectacles (particularly short-sighted persons) should also wear their spectacles when shooting. Especially shooters with astigmatisms should wear their spectacles when shooting. The dioptre compensation of the rifle scope is not able to correct astigmatisms because the development of this ametropia is too individual.

Image defects are most common when using progressive-addition lenses while shooting. Due to the construction of these lenses, the shooter is only able to use a narrow optical channel. If the shooter deviates from this optical channel when aiming, image distortions occur which can show as star-shaped, frayed light spots or arched reticle bars. Additionally, the image as such becomes blurry.

The selection of the spectacle frame is another crucial criterion. If the spectacle frame is too small, the shooter looks directly onto the edge of the frame while aiming. This could cause image doublings or scotomas. Hence, a sufficient size of the spectacle lenses, especially towards the top, must be ensured.

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Reflection sights

How do I mount the DOCTERsight?

The DOCTERsight can be mounted to almost all weapons. Your gunsmith will provide specialist advice on the mounting type. Leading mounting manufacturers offer the corresponding DOCTERsight adapter plates for almost all weapon installations. An adapter plate is even available for the high-quality SHM (Suhler hook-mounting) which, however, must be adjusted to the individual weapon by a specialised gunsmith.

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How far can I shoot using the DOCTERsight?

The DOCTERsight was developed for shooting distances from 20 m to max. 60 m – typical distances for drive hunts. In terms of pure technology, it is certainly possible to shoot larger distances, however, a clear shot as well as a secure identification becomes increasingly difficult due to the single magnification and the increasing point coverage.

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Do I have to open both eyes when sighting?

It is generally possible to target using both or only one eye. The advantage of targeting with both eyes open is the utilisation of the maximum own visual field. Due to the single magnification, there are no confusing double images forcing the brain to block out an image impression when targeting using both eyes.

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Why does the dot not appear round?

The functional principle of the point display is based on total internal reflection. As any reflection, this one can also be influenced by certain factors. Here, certain light sources which can cause disturbing side reflections and therefore no longer let the dot appear as a circle are decisive. One of these disturbing light sources is the low sun coming transversely from the front.

Another significant influencial factor is the human eye. Our eye tends not to depict dot-shaped light sources as circles, especially if a certain light intensity is exceeded. This phenomenon can be observed very well when looking at a burning candle. If you look directly into the flame, a serrated corona will appear around it. This impression is only created by the depiction inside the eye.

Ametropias, especially astigmatisms, can also make dot-shaped light sources appear uneven or serrated. This ametropia does not necessarily have an effect on the daily visual tasks and therefore, it remains unnoticed. In most cases, a dot-shaped light source will then appear serrated at one side when looking at it.

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Binoculars

Where can I buy DOCTER binoculars?

DOCTER binoculars can be purchased from special hunting retailers, established gunsmiths, opticians and special photography retailers.

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Which is the right binocular for me?

As diverse as the application of a binocular, as diverse the selection of models. But one thing applies to all: the application determines the type of the binocular. If you need a binocular for hiking, stalking, raised hide hunting during the day, drive hunting or the Sunday stroll, you will decide on a model with compact design and an lens diameter between 30 mm and 42 mm. Binocular models with eyepiece diameters beyond 50 mm are mostly used for raised hide hunting or stationary observations.

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What is the difference between Porro and Roof Pentaprism binoculars?

Binoculars with porro prisms are characterised by a clear offset between lens and eyepiece, with the lenses set towards the outside in the binocular arrangement of two telescopes. This design goes back to the one patented by Ernst Abbe in 1893 which established the construction of binoculars. There are two different configurations, with the Porro systems of the first type being more common. Approximately with the beginning of the 1920’s, other binoculars using different prism inverting systems have been developed and manufactured at larger numbers, with a reflection surface designed as a roof pentaprism being typical here. These systems can be developed between the incoming and outgoing beam without an axis offset. Typical prism systems with roof pentaprism are named after König, Uppendahl or Schmidt-Pechan which is probably the most prevalent one. Optical perfomances:

  • Porro prism systems avoid the system-related disadvantage of a prism set with roof pentaprism in the form of polarisation effects which, for this type of inverting system, can only be reduced by highest precision and phase-correcting coating on the roof pentaprism.
  • For a system according to Porro, the reflection on the catheti surfaces of the prisms is realised by utilising the effect of total internal reflection and therefore, it is almost loss-free. No sensitive and transmission-reducing mirror layers are required.
  • Due to the luting of the two individual prisms, as it is used in, for example, DOCTER, the number of optically effective surfaces reduces from 8 to 6 and therefore, the possibility of negative effects on the image performance is also reduced. At the same time, the transmission is increased due to the avoidance of two glass-air surfaces. A roof pentaprism system according to Schmidt-Pechan has 10 effective surfaces which are influencing the image. 
  • The clear guidance of the beam through the prism system and the avoidance of light interspersions due to a suitable design of the prism support enable a high image contrast. The occurrence of brightenings at the light exit on the lens side (side pupils) which also cannot always prevented in high-quality roof pentaprism glasses, is completely excluded and enables a high brilliance. 
  • With a Porro prism system it is possible to realise significantly larger beams which are guided through the prisms without loss. With the same lens diameter, the fully transmitted beams are typically twice as big as in roof pentaprism binoculars. This also results in a brighter image towards the edges of the image than what is usual for roof pentaprism glasses, as well as a better suitability for twilight.

(Source: A. Köhler from www.akoehler.de)

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Why large eyepiece diameters for observations in the dark?

The size of the exit pupil of the binocular is decisive for the amount of light arriving at the eye. As this diameter is calculated from the quotient of lens diameter and magnification, the lens diameter has a significant influence on the night-suitability of the binocular.

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How does the exit pupil diameter affect the observation comfort?

Ideally, the size of the exit pupil of the binocular has the same diameter as the entrance pupil of the observing eye. Only if this is the case, the full luminous power of the binocular is used by the observer. The pupil width of the human eye is individual. The opening capability of the pupil of the eye decreases over the years but a general specification of numbers is not recommendable. For example, not every 20-year-old has a pupil opening of max. 7 mm and not every 60-year-old has a pupil width of 3 mm. But it is safe to say one thing: an exit pupil of a binocular which is larger than the pupil of the eye brings advantages in terms of observance comfort. The edges of the aperture are perceived less and the restlessness of the observer's hands shows less by spinning and shaking edges of the visual field. The user will not be able to utilise the full luminous power of the binocular but he will receive a steadier image instead.

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Why do lenses have to be coated and how can I identify the coating?

Lenses must be coated in order to ensure the maximum light transmission. For physical reasons, it is not possible to reach a transmission of 100 %. Hence, residual reflections can be seen on the lenses of binoculars which are appearing in different colours, depending on the type of the coating.

The colour appearance of an anti-reflection coating (coating layer) results from the not entirely linear course of the remaining reflection across the wavelength range. This remaining reflection is largely determined by the type of the anti-reflective coating (single layer, multilayer coating or broadband anti-reflective coating), the position of the reflection minimum, the used recipe of the coating system (material selection, layer thickness and layer sequence), the refractive index of the base material as well as production scatterings (deviations in layer thickness and position within the evaporation plant).

The traditional single layer coating using MgF2 typically shows a blue colour. Multilayer coatings often appear violet but can also have a different colour such as blue, if the reflection minimum is shifted to red. Modern broadband anti-reflective coatings are often slightly green because the reflection is slightly higher in the medium range (green) within the very large spectral range in which the reflection is very low. This is already perceived as colour.

(Source: A. Köhler from www.akoehler.de)

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Lighting technology

What are the differences between the three DOCTERaspherilux torch types?

The torches of the aspherilux midi range differ from each other in terms of the housing type, energy supply and the used illuminant. For detailed information on the lamp models, please click here!

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How do you get the circular spot?

Most torches work with a reflector behind the illuminant according to the principle of total internal reflection. The reflected light is then undirected by means of a usually plane parallel plate and reflected towards the outside. This can cause scattering and shading in the luminous field. DOCTER torches use an aspheric lens instead of the transparent disc. This gives the light beams a precise deviation and a clean, circular spot is resulting. For further information, please click here!

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What is the difference between halogen and LED?

The main difference between the two luminants is the different power consumption and colour temperature of the light spot. LEDs require significantly less power than halogen bulbs which enables an operating time of 10 hours without changing the battery. The colour of the LED spot appears bluish whereas the halogen lamp generates a yellow light colour.

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Why are DOCTER torches flat?

The flat shape has established in practical use. Due to this, the lamps fit into every pocket and an unintended rolling of the lamp is also prevented.

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