Periscope vs. Episcope

[MBT 70 A GO GO]

Hi all,

 

It is my understanding that the difference is that the periscope can move (elevation/azimuth?) and an episcope is fixed. Is this right or is there more to their differences?

 

Thanks,

 

Tony

[rmgill]

I think Episcope is a "british" term no?

 

I've seen the periscope that goes down and not up on the front of the daimler AC described as an episcope. ie the Gunner's view out is lower than his head, closer to the turret ring.

[shep854]

I don't know if this helps, but here's an image of a "protectoscope" on an M3 Stuart, from World of Tanks:

http://wiki.worldoftanks.com/index.php?title=File:M3_light_tank%27s_pistol_port_and_protectoscope.png&oldid=5701

Is this also known as an "episcope"? It appears to be a periscope for viewing through a vertical surface.

[rmgill]

Some period reference...

 

Note the Periscope in the roof and the episcope behind the telescope for the gunner.

 

 

 

On british vehicles they have "screens" in front of the vision viewing devices for protecting the driver's eyes from glass spinters and bullet splash. Vision Block seems correct....

 

[DB]

Online references aren't of much help, except perhaps that an episcope is supposed to project an image onto a screen, whereas a periscope doesn't.

 

Do episcopes have a "viewing screen" - like there used to be on those big, old fashioned plate cameras?

[DougRichards]

From Crow and Hicks 'Encyclopedia of Tanks' (1975):

 

Episcope: A pivoted or ball mounted periscope.

 

Periscope: An optical device using mirrors or prisms by means of which a viewer's eyes are below the actual line of sight.

[shep854]

Online references aren't of much help, except perhaps that an episcope is supposed to project an image onto a screen, whereas a periscope doesn't.

 

Do episcopes have a "viewing screen" - like there used to be on those big, old fashioned plate cameras?

I had the same problem when I tried Google; the modern "episcope" seems to be what I've always called an "overhead projector", as opposed to the viewing device we're discussing.

----

Doug, does that encyclopedia have a definition/description of a protectoscope?

Edited January 15, 2012 by shep854

[DougRichards]

I had the same problem when I tried Google; the modern "episcope" seems to be what I've always called an "overhead projector", as opposed to the viewing device we're discussing.

----

Doug, does that encyclopedia have a definition/description of a protectoscope?

 

Sorry, it doesn't list that in the glossary. I have looked right through in case it appears as a note in another definition, or if the term appeared in the 'desgn' chapters, but no luck.

[shep854]

Sorry, it doesn't list that in the glossary. I have looked right through in case it appears as a note in another definition, or if the term appeared in the 'desgn' chapters, but no luck.

Thanks; it was apparently limited to pre- and early-WWII, and strictly American at that.

There is some discussion in one of Hunnicutt's books. What I recall is that protectoscopes fell out of favor as armor became thicker and because of limited FOV compared to periscopes. I'll try to locate and upload.

Edited January 15, 2012 by shep854

[DougRichards]

Thanks; it was apparently limited to pre- and early-WWII, and strictly American at that.

There is some discussion in one of Hunnicutt's books. What I recall is that protectoscopes fell out of favor as armor became thicker and because of limited FOV compared to periscopes. I'll try to locate and upload.

 

There is one more 'scope' mentioned, and that was the French geoscope, that had a small objective lens but a larfe exit lens, which is further noted as the view was annoying because motion was exaggerated. That sounds almost like one of those front door peepholes.

Edited January 15, 2012 by DougRichards

[rmgill]

From Crow and Hicks 'Encyclopedia of Tanks' (1975):

 

Episcope: A pivoted or ball mounted periscope.

 

Periscope: An optical device using mirrors or prisms by means of which a viewer's eyes are below the actual line of sight.

 

Huh...

That's funny because British use in WWII appears to be the opposite.

[rmgill]

Thanks; it was apparently limited to pre- and early-WWII, and strictly American at that.

There is some discussion in one of Hunnicutt's books. What I recall is that protectoscopes fell out of favor as armor became thicker and because of limited FOV compared to periscopes. I'll try to locate and upload.

 

Well, there's the other issue in that the armor is by necessity thinner there for the view slits and the cone shaped viewing space.

[Tony Williams]

Online references aren't of much help, except perhaps that an episcope is supposed to project an image onto a screen, whereas a periscope doesn't.

 

Do episcopes have a "viewing screen" - like there used to be on those big, old fashioned plate cameras?

Decades ago I used to work with a device called (in the UK anyway) an epidiascope. This was a cumbersome device used in teaching to project images of solid objects or book pages by brightly illuminating them - a mirror and lenses were used to project the magnified image onto a standard large screen. Obviously, the room had to be blacked-out for this to work. Made obsolete long ago by the video camera and projector.

[rmgill]

Decades ago I used to work with a device called (in the UK anyway) an epidiascope. This was a cumbersome device used in teaching to project images of solid objects or book pages by brightly illuminating them - a mirror and lenses were used to project the magnified image onto a standard large screen. Obviously, the room had to be blacked-out for this to work. Made obsolete long ago by the video camera and projector.

 

One of these...

 

http://www.youtube.com/watch?v=_DFn6Dizd5E&t=6m20s

Edited January 15, 2012 by rmgill

[DogDodger]

Doug, does that encyclopedia have a definition/description of a protectoscope?

Protectoscopes were periscopes with an armored pocket to trap bullets or fragments.

[Tony Williams]

One of these...

 

http://www.youtube.com/watch?v=_DFn6Dizd5E&t=6m20s

Something like that, although the one I was familiar with had an enclosed box at the bottom to take whatever needed to be projected. It could therefore project images of solid 3D objects as well as photos and book pages.

 

I see that Wiki makes a distinction as follows:

 

At the beginning of the 20th century, projection was split into two classes: " If the light traverses the object, the projection is said to be diascopic, if by reflected light, episcopic.".[1]

 

Two main classes of opaque projectors thus existed:

 

1.the episcope, which solely projected images of opaque objects

2.the epidiascope, which was capable of projecting images of both opaque and transparent images

 

The closest I can get to the one I used is this, from: http://www.luikerwaal.com/newframe_uk.htm?/epidia_uk.htm

 

[shep854]

Protectoscopes were periscopes with an armored pocket to trap bullets or fragments.

That makes sense; when looking at illustrations they seem awfully periscope-like. My impression was that they were intermediate between a simple viewing slit and the overhead-mounted periscope we're all familiar with.

[Froggy]

In France, an episcope is a vision device that has no mobile part inside (an episcope can have a mobile mount however).

A periscope has a mobile part inside (mirror generaly, and/or magnification change)

[Rob Veenendaal]

Epi or Peri,

 

The answer should be in the meaning of the Greek words Epi and Peri.

Epi seems to mean upon, whilst Peri means around.

So, technically we have the same vision device, but when mounted fixed, it's an episcope and when mounted flexible, it's a periscope.

 

Episcope as we know it seems to be used by tankers only. The rest of the world thinks it's a projector.

 

Tanks also complicate matters because there can be discussion here:

-The whole tank can move, so all is periscopes

-The turret can rotate, making any device Periscope

(In my opinion, It's a periscope when the direct mount allows movement of the device.)

 

So far for the basics, but one also has to consider the part of the world where the term is used.

When mentioning Episcope in the UK, they seem to think you are completely daft.

Similar here in Holland, where Episcope is simply not known.

When mentioning Periscope in New Zealand; They don't seem to know the word.

It would be nice to have some replies here from all over the world, just to find which terms are used where exactly.

Thanks to Froggy,(The above post) we know that the French seem to know the correct terms, though I must say that they also complicate matters by mentioning mobile parts inside the device...

/Rob

Edited January 22, 2012 by Rob Veenendaal

[Max H]

Tanks also complicate matters because there can be discussion here:

-The whole tank can move, so all is periscopes

-The turret can rotate, making any device Periscope

(In my opinion, It's a periscope when the direct mount allows movement of the device.)

To take that to its logical conclusion, every device is an periscope because the earth is not fixed in space. I agree with you - motion relative to whatever it is mounted to should be the defining factor

[shep854]

This is the image I tried to link to back near the top of the thread: is this an 'episcope', with 'protectoscope' simply an Americanism?

http://wiki.worldoftanks.com/index.php?title=File:M3_light_tank%27s_pistol_port_and_protectoscope.png&oldid=5701

[Rob Veenendaal]

I think what we see here is a direct vision block, mounted in a hatch.

That hatch can be opened, but then the block can't be used for viewing. That would indeed make it an epi.

Scope however seems to mean vision device. I am certainly no expert on the matter, but I can't see how a glass block can be named "device".

Most likely, "Protectoscope" sold better than "vision block".

 

/Rob

[shep854]

I think what we see here is a direct vision block, mounted in a hatch.

That hatch can be opened, but then the block can't be used for viewing. That would indeed make it an epi.

Scope however seems to mean vision device. I am certainly no expert on the matter, but I can't see how a glass block can be named "device".

Most likely, "Protectoscope" sold better than "vision block".

 

/Rob

It's an indirect viewing device. Hunnicutt's Stuart has diagrams and photos on pg 137 that shows it as a periscope mounted in the pistol port flap, which meets the description of episcope, if I understand it correctly.

Sadly, I can't bring an image over. I have the book on my hard drive.

[DKTanker]

This is the image I tried to link to back near the top of the thread: is this an 'episcope', with 'protectoscope' simply an Americanism?

I've seen relatively few descriptions for viewing device that included the term "episcope" much less "protectoscope. Now I admit I haven't read every post on this thread, but has there been even one offer of evidence that episcope or protectoscope were used as official descriptive terms by any of the US armed forces.

[shep854]

I've seen relatively few descriptions for viewing device that included the term "episcope" much less "protectoscope. Now I admit I haven't read every post on this thread, but has there been even one offer of evidence that episcope or protectoscope were used as official descriptive terms by any of the US armed forces.

All I've seen is period or historical writing such as Hunnicutt's. This mystifies me as well, since there are tons of references to M-numbers for the various periscopes. Using Google, I've found a couple of "so-so" mentions, incl. a link to Zaloga.

Definition, from thefreedictionary.com:

protectoscope [prə′tek·tə‚skōp]

(optics)

Device in a tank or armored car, similar to the periscope of a submarine; it enables a soldier to see around a shield without exposing himself to enemy gunfire directed at the ports of the vehicle.

 

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

 

 

References from Zaloga's M3 & M5 Stuart Light Tank 1940-45:

http://books.google.com/books?id=AKNgfES1OqkC&pg=PA16&lpg=PA16&dq=protectoscope&source=bl&ots=evnOp7BC2L&sig=k6Jk39QCf8rB6tYn2mbHj3OG2Wo&hl=en&sa=X&ei=n7AcT6jnEKOciAK34IjVCA&ved=0CGoQ6AEwCTgK#v=onepage&q=protectoscope&f=false