Panther Fibel Discussion of Range Estimation

[Mr. Tittles]

Surnont, A. A Zeiss Folding Stereo Telescope. Zeiss Historica, Fall 1995.

This might be a great source if it could be found.

Note that the Germans had these items in WWI but developed the rangefinding element in WWII.

[rexford]

Using trajectory estimates and random scatter, the 75L48 and 75L70 APCBC rounds would have at least a 75% chance of hitting a 2.4m high target at 800m if the initial distance estimates were within the following ranges (triangles against bottom of target):

2.4m High Target at 800m

75L48: 680m to 830m

75L70: 695m to 975m

The gun would actually set for a range 150m greater than the above initial estimates to obtain the final adjusted gun setting.

Shots taken with initial distance estimates within the above ranges would all have at least a 75% chance of hitting the target.

The above estimates assume that the crew does everything by the book and does not make any silly errors, which may have been much rarer than the other extreme.

================================

Earlier analysis of the Panther trajectory showed that adding "1/2 the perceived height in mils times 100m" resulted in a mean trajectory shot placement below the mid-point, whereas using the full viewed height placed the average shot above the mid-point.

Using the lower aim point, 1/2 mils times 100m, makes sense since the target is usually wider below the mid-point and the number of shots up near the relatively narrow turret will be reduced.

[Mr. Tittles]

The panzer commanders binoculars seem to also have some range finding reticle incorporated. Many sources comment on the enhanced stereo effect these regular binos have also. I read an account of a GI who had a captured pair and claimed he could spot two enemy positions with them but did not see them with his GI issued pair.

Does anyone have any info about these German binocular reticles? Is it similar to the strich triangles in the gunners sights?

Rexford's calc:

2.4m High Target at 800m

75L48: 680m to 830m

75L70: 695m to 975m

Why wouldnt the L70 have a lower range number that is greater than a L48? Its error gap should extend both near and far?

In any case, you seem to have changed your mind regarding missing more often than not?

[rexford]

Originally posted by Mr. Tittles:

The panzer commanders binoculars seem to also have some range finding reticle incorporated. Many sources comment on the enhanced stereo effect these regular binos have also. I read an account of a GI who had a captured pair and claimed he could spot two enemy positions with them but did not see them with his GI issued pair.

Does anyone have any info about these German binocular reticles? Is it similar to the strich triangles in the gunners sights?

Rexford's calc:

2.4m High Target at 800m

75L48: 680m to 830m

75L70: 695m to 975m

Why wouldnt the L70 have a lower range number that is greater than a L48? Its error gap should extend both near and far?

In any case, you seem to have changed your mind regarding missing more often than not?

As noted in an earlier post, when the 75L70 range estimate is adjusted for one-half the perceived target height, the average round lands below the mid-point. The 75L48 lands close to the mid-point for the same range estimate and adjustment. So the mean trajectory of the 75L70 will scatter off the target before the 75L48 does as the range is decreased below the actual, since the 75L70 starts off closer to the bottom edge.

And the 75L48 will have a higher hit % than the 75L70 when some of the estimates are less than actual.

[ August 13, 2004, 01:52 PM: Message edited by: rexford ]

[rexford]

The Germans noted that "fire for effect" would be used out to 1200m, and bracketing would be used beyond that range. Daniel speculated that the reason was near 100% first round accuracy below 1200m, but a reading of U.S. gunnery manuals suggests that gun sight limitations on second shot corrections were the cause.

The American field manual for 37mm and 75mm gunnery indicates that out to 1000 yards the gun sight enabled the gunner the correct the aim onto the target using methods such as "burst on target" and other methods. With burst on target, the target is moved on the gun sight to the perceived location of the first shot, which should improve the second shot %.

Beyond 1000 yards the gun sight did not allow the methods to be used very well, so bracketing was substituted.

When the German manuals or instructions indicate that fire for effect is to be used to 1200m, and bracketing beyond that range, it appears that they are talking about the second shot correction methods. I believe that the Fibels do include a some gunnery correction methods with range limitations similar to the Americans (but with a longer range).

[Redwolf]

Originally posted by Mr. Tittles:

The panzer commanders binoculars seem to also have some range finding reticle incorporated. Many sources comment on the enhanced stereo effect these regular binos have also.

I had a pair of German binoculars in my youth. They didn't have triangles, but they had vertical and horizontal semi-transparent lines which allow you to estimate the range to an object if you know the exact height (or vice versus).

This has nothing to do with stereoscopic rangefinding and modifying/measuring the angle of the two tubes.

Also note that while the line method would also work with a monocular, it is generally unsuitable for anti-tank use. The reason is that you rarely see the tank in all its glory, the lower part will almost always be obstructed by vegetables or terrain features. At the very least you would have to wait until it is in full sight which is unacceptable.

I read an account of a GI who had a captured pair and claimed he could spot two enemy positions with them but did not see them with his GI issued pair.

This doesn't have to do with rangefinding features. They just had more precise lenses (less blur) and they let a lot more light in which is a big help for finding hidden things, even in daylight.

[Mr. Tittles]

As far as the German binos:

I did not say it has anything to do with stereoscopic rangefinding. The reason I bring it up is IF the TC is actually calling out targets, range to the gunner, THEN he must have some superior means of guaging (or estimating) the range. Binos ARE stereoscopic in nature and would give better depth perception than the mono sights of a gunner.

Binos would have better magnification I suppose and better depth perception than a mono sight. Certainly, the observation of long and short rounds would be improved.

In a typical turreted panzer that had a mono sight and a TC with just ordinary binoculars (which I suspect most were), I would suggest the TC had the best visual means of estimating range, followed by the gunner and everyone else in the crew a distant third and below.

In a jagdpanzer or StuG, the typical TC would have a scissor scope and perhaps the training/inclination to use the device to measure long ranges in either ambush or in setting up a defense. The scissor scope would certainly give superior spotting ability than regular TC binoculars.

The scissor scopes had a grid reticle in WWII. This could serve the same function as the gunners triangle sight for known height/width targets.

I have corresponded with someone from the Zeiss Historica society and hope to get more info.

[ August 13, 2004, 04:35 PM: Message edited by: Mr. Tittles ]

[Mr. Tittles]

He writes...

For documentation of all of these WWII instruments, I would suggest the book by Dr. Hans Seeger (German Military Technology: The Optical Equipment) available in the US from Deutsche Optik (search for the website) for specific detail. This is a collection of Zeiss catalog data from 1930-1940 but since it was for the German Military only, it is in the German language.

[Mr. Tittles]

Originally posted by Mr. Tittles:

Surnont, A. A Zeiss Folding Stereo Telescope. Zeiss Historica, Fall 1995.

This might be a great source if it could be found.

Note that the Germans had these items in WWI but developed the rangefinding element in WWII.

I was sent a copy of this article. Its only 3 pages but has very nice close up pics.

Whats apparent is that as the scope is scissored out, the eyepieces also move out! Just like when you use a pair of binocs for the first time, you have to angle the hinge element so that the eyepieces line up to your eye seperation. There is a scale on the tubular bar that shows the seperation setting also. Its 55, 60, 65, 70, 75 with ticks between those numbers. This way, you could fold them up and return to the same setting as before.

The implication is that they probably could be used as rangefinders at the different angles. People with large heads and widely seperated eyes would have an increased stereo effect. They would be better then most at finding range.

It appears that all stereo adjustment comes from one knob on the bottom (which has fine markings indicating rotational amounts). The inter-eye-distance number could be used as a correction factor. Crude but doable. So the drill would be sight target, adjust the stereo effect till target image appear 3d, read off the knob and do a math factor based on your interpupillary needs, get a range. A person would then know through experience what the knob readings mean as far as range distance (especially easy if its a linear correlation). It would be very easy to set up tanks at precise distances and have training so that people got to know their SF very well. Guys like Wittman probably kept his because it was like a glove to him. He went from StuGs to Tigers and kept the SF.

The SF in this article are SF14Z and supposedly from WWI. They are clearly from an arty unit and there is a leveling bubble and a finely adjustable scale in the German units (1/400th?).

[ August 13, 2004, 04:34 PM: Message edited by: Mr. Tittles ]

[rexford]

"Whats apparent is that as the scope is scissored out, the eyepieces also move out! Just like when you use a pair of binocs for the first time, you have to angle the hinge element so that the eyepieces line up to your eye seperation. There is a scale on the tubular bar that shows the seperation setting also. Its 55, 60, 65, 70, 75 with ticks between those numbers. This way, you could fold them up and return to the same setting as before.

The implication is that they probably could be used as rangefinders at the different angles. People with large heads and widely seperated eyes would have an increased stereo effect. They would be better then most at finding range."

That scale is explained in the catalog article which shows the scissor scope in periscope and stereoscopic modes, and the scale has NOTHING to do with modifying the range dial readings for arm position. There is no implication that the scale refers to range finding, based on my reading of the text.

The scale has to do with the eye distance changes related to the two modes, and that dial allowed the scissor scope to be used in two modes instead of one. It states this in the catalog article.

Read the article, it explains why there are two dials (one is for interpupillory distance, or something like that).

As I mentioned in an earlier post on this thread, a range dial calibrated for 90cm arm difference will not work when the scissor scope is folded upwards for several reasons:

A. the distance between lenses is no longer 90cm and the range figure on the dial is keyed to a function of angle and lens separation distance

B. the changes in lens angle no longer refer to horizontal changes, making any attempt to relate angle changes to range a nightmare of an exercise.

[Mr. Tittles]

http://home.arcor.de/thuernagel/sf14-e.htm

stereoscopic mode; interpupillary distance approx. 70 mm.

Here we see the SF splayed out and the interpupillary distance DOES go out towards the end of the scale. As said before, the scale goes from 55 to 75. Its the brass bar that runs along the top.

So this supports that the scissors splay out and the interpupillary distance increases.

The only stereo adjustment is the one bottom knob on the lower right. It brings the device into 3D focus by angling the prism (one prism is probably fixed and the other right side is adjusted) The other knob on the side deals with the bubble level (which faces the right side). The other knob, attached to the white piece deals with angle of direction for arty purposes.

The fact remains that humans can not move thier eyes out to the outside of thier heads. They are fixed distances between them. I guess the next guess is that the interpupillary distance could be adjusted AND the scissor scopes splayed out independantly? yeah right.

[ August 14, 2004, 10:11 AM: Message edited by: Mr. Tittles ]

[Mr. Tittles]

A few sources support that the SF did not have to be all the way to see stereoscopic images. Most do state that the further apart they are, the more 3D the images appear (some describe the effect as people appearing to be sculpted). Its apparent then that since there IS just one knob that adjusts this stereo effect (maybe Rexford needs to go back and look again), and that knob does have markings which must be the range scale, there could be a way to correlate those knob readings to actual ranges. Ideally, it would be a linear correlation.

The combination of the clarity of image, depth of perception, graticle and knob readings makes me lean towards range finding with this device.

Someone posted accuracy data before from Spielberger for this device. I would not assume that would be for the end of the scale. It would probably be for the median values on the interpupillary distance.

[Mr. Tittles]

Interpupillary distance

Sometimes abbreviated as IPD, Interpupillary distance is the distance between each of the human adults eye pupils. Interpupillary is a common measurement found in virtual reality devices, microscopes, and binoculars. The average interpupillary distance is between 58 and 72mm.

[Mr. Tittles]

Heres the SF folded and packed in its container. Notice the brass bar is extended on the left eyepiece? Does anyone doubt that the IPD does in fact need the scissor action to be set?

[Mr. Tittles]

I will remind Rexford that the catalog article states he does not have the manual or instructions. I doubt he was trained to use the device. He states the device is not in working order.

The most important information on that site is the pics, IMO.

[rexford]

Originally posted by Mr. Tittles:

A few sources support that the SF did not have to be all the way to see stereoscopic images. Most do state that the further apart they are, the more 3D the images appear (some describe the effect as people appearing to be sculpted). Its apparent then that since there IS just one knob that adjusts this stereo effect (maybe Rexford needs to go back and look again), and that knob does have markings which must be the range scale, there could be a way to correlate those knob readings to actual ranges. Ideally, it would be a linear correlation.

The combination of the clarity of image, depth of perception, graticle and knob readings makes me lean towards range finding with this device.

Someone posted accuracy data before from Spielberger for this device. I would not assume that would be for the end of the scale. It would probably be for the median values on the interpupillary distance.

A whole lot of assumptions regarding the possible measurement of angle/range in the periscopic mode while the physics of the situation suggests that it can't be done.

Suggest that you reread my past posts and get up to speed on the physics and optics problems involved when a device designed for horizontal angle measurement with a range dial calibrated for horizontal arm distance has the arms close to vertical. With arms near vertical, the change in angle per dial turn is neither vertical or horizontal.

And I never said there were two knobs for stereoscopic range changes, just one. The other dial was for the pupil distance.

[Mr. Tittles]

Where exactly do you think this dial for pupil setting is?

[rexford]

Originally posted by Mr. Tittles:

Where exactly do you think this dial for pupil setting is?

Sit down and draw a picture of the stereoscopic range finder with arms horizontal. Horizontal angle that aligns vision is measured by turning dial, where calibration is based on distance between lenses.

Now draw the arms in periscope position, about 25cm apart, and note direction that lens will turn when dial is rotated. VERY DIFFICULT to focus device because angle which changes is no longer horizontal but is at a very odd angle.

And remember that due to the 25cm lens difference the accuracy and image sharpness is going to be seriously degraded.

If you draw the device in horizontal arm position and think about how the angle changes are related to the sight triangle needed to align the views, the great difficulty which follows from the periscopic position may be easier to understand.

The change in angle when the range dial is turned is perpendicular to the arm length, not perpendicular to the horizon or vertical.

There really is nothing more that can be said to explain what is going on short of posting a drawing of my own which illustrates the above noted situation.

Until someone comes up with a manual or document or explanation or something that shows how the TF 14 can be used for stereoscopic range measurement in periscope position, my view is that the physics of the situation makes that result (range measurements in periscope position) highly unlikely.

[Mr. Tittles]

So you dont want to tell us where you think it is?

[Mr. Tittles]

I think the following need to be considered:

1. The device does NOT have to be fully splayed out to see stereoscopically. There are ample photos showing in use when it is not fully splayed out or strait up. In other words, why splay it out at all if not all the way?

2. The means of focusing the 3D image, whether fully splayed out or not, could be correlated to range. So if the same IPD was set and the operator learned the range of values that corresponded to ranges; he would have some means of determining range.

basically I see the SF (not TF) lengthening the abilities of the tank crewmen from sub 1000m to out to 2000m or so.

[rexford]

Originally posted by Mr. Tittles:

I think the following need to be considered:

1. The device does NOT have to be fully splayed out to see stereoscopically. There are ample photos showing in use when it is not fully splayed out or strait up. In other words, why splay it out at all if not all the way?

2. The means of focusing the 3D image, whether fully splayed out or not, could be correlated to range. So if the same IPD was set and the operator learned the range of values that corresponded to ranges; he would have some means of determining range.

basically I see the SF (not TF) lengthening the abilities of the tank crewmen from sub 1000m to out to 2000m or so.

You obviously have not looked at the physics and optics problems that are involved.

[Mr. Tittles]

Optical testing at Aberdeen Proving Ground is shown in the booklet:

Ordnance School. Foreign Materiel, volume 3. (fire control instruments &

sighting equipment, German & Japanese, B.C. scopes, range & height

finders) Published by The Ordnance School: Aberdeen Proving Ground,

Maryland, July 1943. (OS 9-61, vol. 3) 100p.

This has photos, breakdown photos, and brief descriptions of use for

these instruments:

German: aiming circle Rkr 31; B.C. type stereoscopic telescope; range

finder EM 34; illumination lamp for fire control instruments; Z.F.

antitank telescope; 81mm mortar sight.

Japanese: coincidence range finder 75cm base; stereoscopic height finder

2m base.

This is vol. 3 of a series, the first two concerned foreign small arms &

artillery. They were written for use in courses taught at The Ordnance

School. Subsequent volumes were planned.

(Most of the optical related work done at Aberdeen was in the realm of

verifying work done and carrying any overload for Frankford Arsenal,

which has been the principal site for the design, development and repair

of Army optics since approximately 1921. --Earl Osborn)

[Vossiewulf]

You guys are quite the pair;)

Keep it up. Informative and amusing at the same time!

[Mr. Tittles]

Inside a German 250/5. Note again the middle position angle of the device. Many photos show that it is being used at an angle roughly 30-45 degrees.

[Mr. Tittles]

http://www.beobachtungsabteilung.derkessel.de/OOB.html

Scissor scopes in use by counter battery. There is a photo showing them splayed out but not folded all the way down. There is also a photo looking through the right eye piece and it shows the grid overlay that could be used to judge distances.

[ August 19, 2004, 09:52 AM: Message edited by: Mr. Tittles ]