US Navy Infrared Signaling Telescope US/C-3

© Brooke Clarke 2015
US Navy Infrared Signaling Telescope US/C-3 US Navy Infrared Signaling Telescope US/C-3



Discovered a number of these on eBay while looking for military optical stuff.  It appears to be a W.W.II vintage IR telescope.  The Sniperscope (Wiki) and Snooperscope (Time 1963) were of the same vintage and use the same technology. After receipt and installing a couple of "D" cell batteries it worked.  You can hear a hum when the inverter is running and as soon as it stops running the image tube goes dark.  That probably means the the high voltage capacitor is leaky.  The vibrator does not start every time the button is pressed.  The points may need to be cleaned.

M2 Sniperscope with handle (Snooperscope)
heavy battery box, lamp + IR filter, Sniperscope.
                  with handle
YouTube: Forgotten Weapons: M3 Infrared Sniper Carbine at RIA


This is a near IR (not thermal IR) telescope without an associated illumination source.  It's intended to see IR beacons or Aldis signal lights on ships with IR filters.  It would also work to see the M-227 Signal Lamp Equipment SE-11 when the IR filter is in place.  The C-3 does not have the ability to send a signal, only to see an IR signal.

List of early near IR scopes and the image tubes they used:
T120 Sniperscope: IP-25
M1 Sniperscope: IP-25
M2 Sniperscope: IP-25
M3 Sniperscope: CRC-6032A (8000 +/- 1000 angstroms,800 nm, just beyond visible red light i.e. 700 nm)

The A version of the 6032 image tube is the same as the no letter version except specified to see lower light levels specified in lux.  But that's a problem because lux is a visible light specification where the Weston Model 594 Photronic Cell is the basis of "visible" light.  So using light units may have been a mistake when working with a sensor for non visible radiation, even though it's just a little longer wavelength than red light.


Fig 1 Carrying Case
US Navy Infrared
                  Signaling Telescope US/C-3
Fig 2 Instructions in case lid
US Navy Infrared
                  Signaling Telescope US/C-3
Fig 3 Open carrying case
US Navy Infrared
                  Signaling Telescope US/C-3
Fig 4 C-3 IR scope
There are 3 adjustments on the secondary mirror:
A large screw at the top allows access to the X adj,
A large screw at right of photo allows access to the
Y adj,
A hole in the front plexiglass plate allows access
to the Z adjustment.

US Navy Infrared
                  Signaling Telescope US/C-3
Fig 5 C-3 IR scope

US Navy Infrared
                  Signaling Telescope US/C-3
Fig 6 Eyepiece end C-3 IR scope
Warning do not point this instrument
toward sun at any time.
Type: US/C-3
Model: MI-2558 Serial 1636
Manufactured for
Navy Department - Bureau of Ships
by contractor
Radio Corporation of America
Camden, New Jersey
Contract NXss 29734
US Navy Infrared
                  Signaling Telescope US/C-3
Fig 7 Mirror, not lens. 
Adjustment for secondary mirror accessible through
hole in flat plastic front cover.  Flat plate on bottom
for mounting, but to what?
US Navy Infrared
                  Signaling Telescope US/C-3


2506018 Image tube, Flory Leslie E, Morton George A, Ruedy John E, Rca Corp, May 2, 1950, 313/524, 313/110, 313/529, 313/250 - IP-25
patent 2506018
              Image tube

3280356 Image tube with truncated conical anode and a plurality of coaxial shield electrodes, Moor Joseph C, Stoudenheimer Richard G, Rca Corp, Oct 18, 1966, 313/529, 313/107, 250/214.0VT, 313/530 - 10,000 Volts, 2.95" long, 1.88" dia.? model
patent US3280356
            Image Tube


Flashlights - Xenide   AEX25 1500 Lumen HID flashlight
Binoculars in general Orion 9x63 astronomical (note with large (7mm) exit pupil diameter they work well at dusk and dawn)
PAS-6 Metascope IR viewer and source
T3C - Russian monocular Image Intensifier (star light scope)
TVS-2 Crew Served Weapon Sight
M18 IR Binoculars - near IR not hot people or car engines
M32 Periscope 105mm IR Gun Sight
MD-1 Automatic Astro Compass - also can see stars in the daytime
Astro-Compass for sighting Sun & stars
Periscopic Aircraft Sextant - Sun & stars
NextStar60 - cleaver microcontroller telescope using DC motors and shaft encoders
Orion - 9x63 binoculars - When the objective diameter (63 mm) is divided by the power (9X) if the exit pupil size (7 mm) is around 7 mm then the binocs are designed to be used with night adapted eyes, like for looking at the stars or to see things on the ground you could not see with bare eyes.  I once watched a dear swimming while being chased by a dog just after Sunset.  Although I could not see anything with my bare eyes, I could see fine with a pair of 7X50 binocs.  See my Binoculars page for more on star gazing binocs.
Celestron 8" Telescope with Equatorial wedge and tripod- This model has a clock drive but no computer control.  It's big and heavy, not something you pull out for a quick 5 minute look up.  Would be much better if used with a permanent pier.  It takes quite some time to do a Polar alignment, but when done you can find about anything just using the hour angle and declination scales.
Cloud Detection - as part of weather forecasting like used as part of an automated observatory
Hughes Probe Eye far (heat) IR viewer
Shadow or Projection Clocks
PVS-4 Starlight Scope
PVS-5A Night Vision Goggles
UAS-4 Infrared Surveillance System, AN/AAS-14 Infrared Detecting Set, MK-898/AAS-14A Optical Filter Kit
IR Beacon
Thermal Hand Held Imager DFOV
Optics - optical patents - optical bench


“Fight at Night!” U.S. Army Night Vision, 1945-1980 - T120 through PVS-3A
Les Flory - Image Tubes and Night Vision - US Navy Infrared Signaling Telescope US/C-3

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page created 9 Feb 2015.