Updated:  2011-03-17

The tactical visibility rules below again assume a Terran environment for simplicity. However, the concepts should be used in conjunction with the planetary variables above and applied by analogy. For example, the rules for smoke and/or bad weather and vision enhancement could apply in the middle of a relatively "clear" day on a world with an Exotic atmosphere. And a world which has no moon would always be treated as a moonless night.

"Each halving of short range" is for targets within the vision device's short range. For example, a target within ½ the device's short range is at -1 Diff Mod, within ¼ (half of half) is at -2, within 1/8 (half of half of half) is at -3 and so on Difficulty modifiers are also applied according to the size of the target to be spotted. Find these modifiers on the consolidated Target and Spotting Size Table.

Once the basic difficulty level of the Observation task is established based on range, difficulty modifiers due to visibility conditions are applied. Although some vision aids are not affected by certain visibility conditions, unaided eyes are affected by all of them. 

Visibility Conditions: Visibility conditions are of three types: night, weather, and smoke. Each of these conditions adds one or more levels of difficulty to the basic Observation task. Some of these conditions actually prevent the use of some vision aids, as discussed with each aid.

Night: Visibility at night varies considerably, depending on the amount of background light. The referee should assign a background light level of from 1 to 3, with 1 being the brightest, representing a clear night with one or more full moons high in the sky, and 3 being the darkest, a cloud-covered, moonless night. The background light level equals the number of + diff mods applied to the task. However, night modifiers do not affect some systems, see below.

Weather: Weather is characterized as poor (+1 diff mod) and very poor (+2 diff mods), although referees may stipulate even worse conditions. Weather mods apply during daylight as well as night, although these mods do not affect some vision aids.

Smoke: Smoke can be of varying densities as established by the referee, and imposes difficulty modifiers starting with +1 for light smoke. At higher tech levels, artificially generated smoke can prevent the use of radar or ladar by the use of suspended particles.

Spotting Size Table

Multiple Modifiers: All modifiers, from visibility conditions as well as other modifiers, are cumulative.

Encounter Ranges: Player character parties will periodically run into other groups. Roll for the range at which the PC group first becomes aware of the other group, based on terrain and modified by visibility, In poor weather, halve all encounter ranges (except in woods). In very poor weather, quarter all encounter ranges (except in woods). At night, divide all encounter ranges (except in woods) by 3× the background light level, then modify for poor or very poor weather. Woods are unaffected by reduced visibility, as visibility is already so limited that encounter range depends as much on hearing the encounter as seeing it anyway.

Vision-Enhancement Devices: A number of vision aids are available. They have the following effects.

Binoculars: Binoculars are useful only during periods of good visibility (daylight and good weather). Characters equipped with binoculars and who have a good field of view have their Observation asset increased by 1. If they spot a group before its pots them, double the range of the encounter.  Binoculars have no effect in woods and smoke.

Image Intensifier: An image intensifier has the same effect as binoculars, except that characters add 2 to their Observation assets. The device incorporates both telescopic and low light intensification, and has a short range of 250 meters.  Image intensifiers allow their users to disregard up to 2 night diff mods (Le., in background light level 3, only takes a -1 difficulty modifier rather than -3), but are fully affected by weather diff mods. Image intensifiers have no effect in woods or smoke.

Color Enhancement: Color enhancement assists in resolving detail at long distances, and is helpful in detecting camouflage.  Color enhancement devices add 1 to the Observation asset, but are useless in other than daylight and good weather.

LA Goggles: tight-amplification goggles allow characters to see in all but absolute darkness by intensifying ambient light. They have a short range of 100 meters. LA goggles allow characters to disregard up to 2 night + diff mods, but they are fully affected by weather diff mods, and have no effect in woods or smoke.

IR Goggles: Infrared goggles allow characters to see heat sources at night, and have a short range of 100 meters. In addition, characters wearing infrared goggles can see the beam of an IR spotlight (immediately below). IR goggles are not affected by night diff mods, but have no effect in woods, smoke or poor or very poor weather.

IR Spotlight: An infrared spotlight can illuminate an area 20 meters across at a range of up to 1000 meters. Only characters wearing IR goggles can see the light, and they make Observation rolls against targets within the illuminated area as if it were daylight. However, any character within 3000 meters and wearing IR goggles will see the searchlight IR spotlights have no effect in woods, smoke, or poor or very poor weather.

White Light Spotlight:  A white light spot light will illuminate an area 20 meters across at ranges up to 2000 meters, and allow characters to make Observation rolls against targets within the illuminated area as if it were daylight. The light itself can be seen by any character at any distance who has a clear line of sight to it White light spotlights have no effect in woods, smoke, or poor or very poor weather.

Thermal Viewer: A thermal viewer is an advanced form of infrared imaging, sometimes called forward-looking infrared (FLIR), although this is a misnomer when the device allows all-around visibility. Thermal viewers are not affected by nig ht diff mods, and the thermal viewer allows characters to disregard up to 1 + diff mod due to weather (thus poor weather has no effect and very poor weather only applies a +1 diff mod), and up to 1 + diff mod due to smoke. It has a short range of 400 meters.  Thermal viewers have no effect in woods.

Wide Spectrum Visual: This device combines the capabilities of light intensification and thermal viewing above. It has a short range of 400 meters and adds 2 to the Observation asset of characters using it. It is not affected by night diff mods, and allows characters to disregard up to 1 + diff mod due to smoke. The WSV viewer is affected by weather mods, and has no effect in woods.

Illumination Rounds: An Illum round will illuminate the area within its burst radius as if it were full daylight.  Illum rounds have no effect in woods, smoke, or poor or very poor weather.

Sensors: All of the above weapons are vision aids, and are used with the Observation asset. The equipment below allows objects to be detected under poor conditions, although not visually, and are used with the Sensors asset instead of Observation.

Radar: Personnel with all-weather radar sensors (usually vehicle-mounted or as portable ground sets) do not have their visibility within the radar's range and line of sight affected by any atmospheric conditions. Radars have a listed short range and calculate difficulty in the normal ways, and use all of the modifiers from the "Other Modifiers" section above.  Radar can, however, be jammed. See Jamming.

Ladar: Ladar works like radar, but uses laser instead of radio pulses. Ladar cannot be jammed, but is degraded by smoke and bad weather at tech levels below 13.