Kestrel 4500NV Horus - the Complete Ballistics Package | RPR Ltd
Kestrel 4500NV with HORUS Kestrel 4500NV with HORUS Kestrel 4500NV with HORUS Kestrel 4500NV with HORUS Kestrel 4500NV with HORUS
5-Year Warranty on all Kestrels

Kestrel 4500NV with HORUS ATrag Ballistics

Product code: K4500HORUS - 0845H

£0.00 inc. VAT

This product has now been superseded by the Kestrel 5000 Range Sportsman & Elite. Please call our office on +44 (0) 1590 641223 to discuss your requirements.

Kestrel & Horus

The Kestrel 4500NV Pocket Weather Tracker with integrated HORUS® Atrag™ ballistics software calculates precise aiming solutions based on real-time atmospheric conditions, user specific ballistics and multiple target data.

When shooting long range, even the lightest of breezes will affect the bullet, no matter what speed or ballistic coefficient it has. Also, any change in geographical location (determining coriolis and spin drift) or altitude, atmospheric pressure, temperature and humidity will impact the firing solution required to hit the target. In a robust, pocket sized instrument the Kestrel provides instant and accurate measurement of wind speed and direction with all other critical environmental parameters that affect a bullet's trajectory. The integrated HORUS software automatically updates the firing solution based on this real-time weather data. Each user inputs their own ammunition's ballistic variables and velocity along with the rifle's data (bore-sightline height, twist rate and direction along with zero range etc.) into the Kestrel 4500NV HORUS. These gun and bullet settings may be saved to a library for future quick reference.

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Target Screen

Kestrel Horus Target Screen Once the ballistic data is entered, the direction of fire (DoF) is programmed using the Target Screen. This is done by pointing the unit at the target from the firing position and pressing 'Capture' to log it. This sets the compass bearing of the target so the crosswind effect can be computed.

Main Screen

Kestrel Horus Main Screen The Main HORUS Screen displays the critical data for making the shot. When the Kestrel is in full automatic mode, the Horus software will immediately calculate the windage (W) and elevation (E) setting for this specific shot scenario, constantly updating the firing solution as long as the unit remains facing into the wind. If preferred, an average wind speed may be captured or a value manually entered. Up to five targets may be active at any time and it is quick to switch between their respective firing solutions.

Range Card Screen

Kestrel Horus Range Card Screen The Range Card Screen shows detailed information about the ballistic solution at various ranges for the currently selected gun & target. Should a correction be required to the theoretical ballistic data based on observations in the field, a 'True Drop' adjustment may be made so that the elevation correction matches what is actually observed to significantly enhance overall accuracy.

Environment Screen

Kestrel Horus Environment Screen The Kestrel 4500NV HORUS also operates as standard Kestrel 4500 Weather Meter providing readings of wind speed and direction, crosswind, headwind / tailwind, temperature, wind chill, heat index, dew point, relative humidity, barometric pressure, altitude, density altitude, wet bulb temperature, digital compass and time & date.

The Kestrel 4500NV with Horus Vision software is a unique high end precision shooting tool. It combines critical environmental data from the Kestrel 4500 with an integrated targeting software solution using Horus ATrag advanced proprietary ballistics algorithms.

Horus Mode

Gun Selection

• Pre-loaded library guns - up to 50 may be stored. The Kestrel is supplied with an initial selection; in the future more may be downloaded to the Kestrel from a PC using new Gun Library Software.
• User-defined guns - up to 9 may be stored
• Default gun - one may be specified

Gun Parameters

• Gun Name
• Muzzle velocity
• Ballistic coefficient (of the bullet)
• Bullet weight
• Bullet diameter
• Zero range
• Bore Height
• Rifling Twist
• Twist Direction
• Scope Clicks
• True Drop

Target Selection

• Up to 5 active targets may be specified for fast switching between

Target parameters

• Target range
• Wind direction
• Wind speeds 1 and 2 (high & low for bracketing)
• Direction of fire
• Inclination angle (for shooting above or below the horizontal)
• Target speed
• Target direction of movement

Environmental Parameters

• Auto or manual update mode
• Latitude
• Temperature
• Station Pressure
• Relative Humidity
• Density Altitude
• Coriolis correction on or off

Ballistics Solution

Corrections for

• Elevation
• Wind speeds 1 and 2
• Lead
• Vertical and horizontal components of coriolis
• Drift
• Remaining velocity
• Remaining energy
• Time of flight
• Max ordinance
• Bullet drop
• Range at which bullet slows to Transonic Velocity and a subsonic velocity

Range Card Screen

• Adjustable range increment - 10, 20, 25, 50 or 100 metres (or yards)
• Range values up to 4000 metres (or yards)
• Display of several parameters of the ballistic solution and their values corresponding to each range increment, including corrections for:     • Elevation
    • Wind Speeds 1 and 2
    • Lead, plus:
    • Remaining energy
    • Time of flight
    • Max ordinance

Weather Mode

• Current wind speed
• Average wind speed
• Maximum wind speed
• Wind direction
• Crosswind
• Headwind/tailwind
• Temperature
• Wind Chill
• Heat index
• Dew Point
• Relative Humidity
• Barometric pressure
• Altitude
• Density altitude
• Wet bulb temperature
• Digital compass
• Time & Date

Choice of measurement units

• kt, m/s, km/h, mph, ft/min, Beaufort
• °, cardinal points
• °C, °F
• %
• mbar, inHg, hPa, psi
• m, ft


• Speed ±3% of reading or ±0.1m/s
• Direction ±5°
• Crosswind, headwind, tailwind ±5%
• Temperature ±1°C
• Relative humidity ±3%
• Dew point ±2°C
• Barometric pressure ±1.5mbar

Operational Range

• Speed 0.6 to 60 m/s
• Direction 360°
• Crosswind, headwind, tailwind 0.6 to 60 m/s
• Temperature -45 to +125°C
• Relative humidity 0 to 100%
• Barometric pressure 10 to 1100mbar

Specification Range

• Speed 0.6 to 40 m/s
• Direction 0 to 360°
• Crosswind, headwind, tailwind 3.8 to 40 m/s
• Temperature -29 to +70°C
• Relative humidity 5 to 95%
• Barometric pressure 750 to 1100mbar

For those with after dark requirements, the Kestrel 4500NV Horus comes with a low intensity red back-light to preserve night vision.

To enable in depth analysis of data at a later time, the Kestrel with Horus ATrag ballistics can be set up to log data automatically or manually. The stored data can also be uploaded to a PC via an additional Kestrel PC interface. With the Bluetooth model, data may be streamed live via Bluetooth wireless technology.

The Kestrel with Horus ATrag ballistics is compact and weighs only 112g. It is IP67 waterproof and MIL-STD-810F rugged. The Kestrel's robust design has survived years of use by the military world-wide; their quality is backed up by a 5 year warranty.

The Kestrel with Horus ATrag ballistics is powered by two easily replaceable, AAA batteries and has two power saving modes to prolong battery life.

Available options

• Night Vision model
• Bluetooth model

Kestrel Horus features

• Multifunction instrument
• Graphical three-line displays
• Data capture up to 2500 readings
• Minimum/maximum/average values
• User defined screens
• Language selection
• Compact, rugged design
• High accuracy
• High precision axle and low-friction Zytel bearings
• User-replaceable impeller
• Fast response temperature sensor
• Easy to read back-lit display
• NV version in olive drab or desert tan has red backlight
• Hard cover protects impeller
• Runs from 2 AAA batteries
• Data upload (with optional PC interface or integrated Bluetooth wireless technology)
• Available in olive drab or desert tan
• 5 year warranty
  Feature Abbreviation Units Min Max
Target Active Targets - A through E 1 5
Target Range TR yards 25 4000
metres 23 3658
Wind Direction WD o'clock 1 12
degrees 0 360
Wind Speeds 1 and 2 (for bracketing) WS1 or WS2 mph 0 50
m/s 0 22
km/h 0 80
fps 0 73
knots 0 43
Direction of Fire DoF o'clock 1 12
degrees 0 360
Inclination Angle Ideg degrees 0 60
Inclination Cosine Icos - 1.000 0.500
Target Speed TS mph 0 50
m/s 0 22
km/h 0 80
fps 0 73
knots 0 43
Target Direction of Movement TD Left to Right OR Right to Left
Gun Name Characters - 0 through 9; A-Z; a-z; -+/.:&* and space
Muzzle Velocity MV fps 300 3400
m/s 91 1372
Ballistic Coefficient BC - 0.100 2.000
Bullet Weight BW grains 10 1500
grams 0.6 97.2
Bullet Diameter BD inches 0.10 1.00
mm 2.54 25.40
Zero Range ZR yards 25 1000
metres 23 914
Bore Height BH inches 0.10 5.00
cm 0.25 12.70
Rifling Twist RT inches/revolution 1.00 36.00
cm/revolution 2.54 91.44
Twist Direction RTd Left OR Right
Rifling Click /mil 1 10
/tmoa 1 10
Environment Latitude Lat degrees 90S 90N
Temperature Temp °F -50 140
°C -46 60
Station Pressure SP inHg 12.00 32.00
mb 406.4 1083.6
hPa 406.4 1083.6
psi 5.89 15.72
Relative Humidity RH % 1 100
Density Altitude (computed) Dalt ft -10732 32767
metres -3271 9987
Coriolis Coriol Yes OR No
Primary Measurement Units Resolution Accuracy
(if less)
Wind Speed
or Air Velocity
m/s 0.1 Larger of 3% of reading, least significant digit or 20 ft/min 0.6 to 60.0 m/s
0.6 to 40.0 m/s
1 inch diameter impeller with precision axle and low-friction Zytel® bearings.
Start-up speed stated as lower limit, readings may be taken down to 0.4 m/s | 79 ft/min | 1.5 km/h | .9 mph | .8 kt after impeller start-up.
Off-axis accuracy -1% @ 5° off-axis; -2% @ 10°; -3% @ 15°.
Calibration drift < 1% after 100 hours use at 16 MPH | 7 m/s.
Replacement impeller (NK PN-0801) field installs without tools (US Patent 5,783,753).
ft/min 1 18 to 11,811 ft/min
118 to 7,874 ft/min
km/h 0.1 2.2 to 216.0 km/h
2.2 to 144.0 km/h
mph 0.1 1.3 to 134.2 mph
1.3 to 89.5 mph
knots 0.1 1.2 to 116.6 knots
1.2 to 77.8 knots
Beaufort 1 0 to 12 B
Temperature °F 0.1 1.8 °F -49.0 to 257.0
-20.0 to 158.0
Air, water or snow temperature. Hermetically-sealed, precision thermistor mounted externally and thermally isolated (US Patent 5,939,645) for rapid response. Airflow of 2.2 mph | 1 m/s or greater provides fastest response and reduction of insulation effect. Calibration drift negligible.
°C 0.1 1.0 °C -45.0 to 125.0
-29.0 to 70.0
Relative Humidity %RH 0.1 3.0 %RH 0.0 to 100.0%
5.0 to 95.0% non-condensing
Polymer capacitive humidity sensor mounted in thin-walled chamber external to case for rapid, accurate response (US Patent 6,257,074). To achieve stated accuracy, unit must be permitted to equilibrate to external temperature when exposed to large, rapid temperature changes and be kept out of direct sunlight. Calibration drift +/- 2% over 24 months. RH may be recalibrated at factory or in field using Kestrel Humidity Calibration Kit (NK PN-0802).
Pressure inHg 0.01 typical 0.04 inHg
max 0.07 inHg
0.30 to 32.48 inHg Air pressure at the location. Adjustable reference altitude allows display of station pressure or barometric pressure corrected to MSL. Monolithic silicon piezoresistive pressure sensor with second-order temperature correction. Pressure sensor may be recalibrated at factory or in field. Kestrel 2500 and 3500 display continuously updating three-hour barometric pressure trend indicator: rising rapidly, rising, steady, falling, falling rapidly. Kestrel 4000 series displays pressure trend through graphing function.
hPa (mb) 0.1 typical 1.5 hPa
max 2.5 hPa
300.0 to 1100.0 hPa 10.0 to 1100.0 hPa
PSI 0.01 typical 0.02 PSI
max 0.04 PSI
0.14 to 15.95 PSI
Wind Direction
Forward Heading
° 1 0 to 360° 2-axis solid-state magnetoresistive sensor mounted perpendicular to unit plane to permit operation while measuring wind speed. Declination/variation adjustable for True North readout. Accuracy of measurements dependent upon unit's vertical position. Self-calibration routine eliminates magnetic error from batteries or unit and must be run after every full power-down (battery removal or change).
Cardinal 16 Points 0 to 360°
Crosswind &
mph 1 10% Refer to stated ranges for wind speed. Effective wind relative to a target or travel direction. Calculated from wind speed, wind direction and target heading. Auto-switching headwind/tailwind indication.
ft/min 1 10%
km/h 0.1 10%
m/s 0.1 10%
knots 0.1 10%
Wind Chill °F 0.1 1.8 °F Refer to stated ranges for wind speed and temp. Perceived temperature resulting from combined effect of wind speed and temperature. Calculated based on the NWS Wind Chill Temperature (WCT) Index, revised 2001, with wind speed adjusted by a factor of 1.5 to yield equivalent results to wind speed measured at 10 m above ground. Specification temperature limits established by WCT Tables.
°C 0.1 1.0 °C
Heat Index °F 0.1 3.6 °F Refer to stated ranges for temp. and relative humidity. Perceived temperature resulting from the combined effect of temperature and relative humidity. Calculated based on NWS Heat Index (HI) tables. (Specification temperature limits established by HI tables.)
°C 0.1 2.0 °C
Wet Bulb Temperature (Psychrometric) °F 0.1 3.6 °F Refer to stated ranges for temp., relative humidity and pressure. Temperature indicated by a wet bulb psychrometer under forced aspiration. Calculated from temperature, relative humidity and pressure.
°C 0.1 2.0 °C
Dewpoint °F 0.1 3.6 °F Refer to stated ranges for temp. and relative humidity. Temperature to which the air must be cooled at a constant pressure for water vapour to condense into water. Calculated from temperature and relative humidity.
°C 0.1 2.0 °C
Altitude ft1 typical 50 ft
max 98 ft
-2,300 to 85,000 ft Height above Mean Sea Level ("MSL"). Temperature compensated pressure (barometric) altimeter requires accurate reference barometric pressure to produce maximum absolute accuracy.
m 1 typical 15 m
max 30 m
-700 to 25,900 m
Density Altitude ft 1 246 Refer to stated ranges for temp., relative humidity and pressure. Air density converted to equivalent sea level elevation at the International Standard Atmosphere. Calculated from temperature, pressure and relative humidity.
m 1 75
Max/Avg Wind Max and average wind calculation may be started and stopped independently of data logging of other values, along with all other wind-related functions: air velocity, crosswind, headwind/tailwind, wind chill, WBGT, TWL, evaporation rate.
Data Storage & Graphical Display, Min/Max/Avg History Minimum, maximum, average and logged history stored and displayed for every measured value. Large capacity data logger with graphical display. Manual and auto data storage. Min/Max/Avg history may be reset independently. Auto-store interval settable from 2 seconds to 12 hours, overwrite on or off. Logs even when display off except for 2 and 5 second intervals (code version 4.18 and later). Data set capacity by model shown.
Data Upload Requires optional PC interface (USB or RS-232) or Bluetooth enabled model and provided software.
Available Bluetooth®
Data Connect
Adjustable power consumption and radio range from up to 30 ft | 9 meters. Individual unit ID and 4-digit PIN code pre-programmed for easy identification and data security when pairing and transmitting. Employs Bluetooth Serial Port Protocol for data transmission.
Display & Backlight Multifunction, multi-digit monochrome dot-matrix display. Choice of aviation green or visible red (NV models only) electroluminescent backlight. Automatic or manual activation.
Response Time & Display Update All measurements except those based on relative humidity respond accurately within 1 second. Relative humidity and all measurements which include RH in their calculation may require as long as 1 minute to fully equilibrate to a large change in the measurement environment. Display updates every 1 second.
Clock / Calendar Real-time hours:minutes:seconds clock, calendar, automatic leap-year adjustment.
Operational & Storage Temperature Range The operational temperature range of the liquid crystal display and batteries is 14° F to 131° F / -10 °C to 55 °C. Measurements beyond the operational range can be taken by briefly exposing unit to extreme conditions such that the display and batteries remain within the operational range. Storage range -22 °F to 140 °F / -30 °C to 60 °C.
Auto Shutdown User-selectable -- 15 or 60 minutes with no key presses or disabled.
Languages English, French, German, Italian, Spanish.
Certifications CE certified, RoHS and WEEE compliant. Individually tested to NIST-traceable standards (written certificate of tests available at additional charge).
Battery AAA Alkaline, two, included. Average life, 400 hours of use, reduced by backlight or Bluetooth radio transmission use.
Environmental Waterproof (IP67 and NEMA-6). MIL-STD-810F, Transit Shock, Method 516.5 Procedure IV; unit only; impact may damage replaceable impeller.
Size & Weight 5.0 x 1.8 x 1.1 in / 12.7 x 4.5 x 2.8 cm, 3.6 oz / 102 g.
Colour Options Olive Drab | Desert Tan
The manufacturer reserves the right to amend the specification and therefore the information in this document may be subject to change
Data Sheet
Kestrel 4500NV with HORUS ATrag Ballistics Data Sheet
User Instruction Manual
Kestrel 4500NV with HORUS ATrag Ballistics Instructions
Horus Ballistics Downloads
Horus Gunloader Software (ZIP file)
(currently not compatible with software version 4.76)
Horus Help files (ZIP file)
Certificates of Conformity
Sample Certificate of Conformity
Kestrel Product Catalogue
Kestrel Pocket Weather Meters Product Catalogue 2012