U-Boot Periscope Telemeters

[Nikdunaev]

Originally Posted by derstosstrupp

I agree yeah seems odd, the numbering. My understanding was it was always early war scopes that had that integrated system. That system was developed after World War I. The C/2 I want to say came around in early 1940, at least that’s the earliest I see it being referred to in the KTBs. The type 21 had the C/2, as well, not sure about any of the other late war boats. Early war attack scopes looked like the one you have pictured. That scope can be seen today in the Vesikko submarine in Finland, a prototype of the Type II.

Sorry, what exactly are the KTBs?
You are saying that the stadimeter and the adjustable stand scope never actually coexisted in one unit, is that right?

I am curious, why could they not, say, take the boat one or two meters deeper, and use the normal, full length scope, with the same effect of it sitting low? Especially in quiet weather, when scope is most visible, but depth control is also easier and more precise...

Originally Posted by derstosstrupp

Speed calculations were typically by matching on the surface, or rough plotting. If they did not have the opportunity to follow the target on the surface, and had to dive quickly upon sighting, they fell back on either eyeball estimation or the fixed wire method, which we are familiar with, timing the target from bow to stern, but based on an estimate of the target length, since they never quite knew this exactly.

These guys simply just got very close, 500 to 1000 m. They were very skilled at eyeballing angle on bow, and range was mostly irrelevant because they shot at low gyro angles, so that whole unit was really redundant in practice.

Did they plot on the map? Maneuvering board? I assume they did not have a device similar in function to the allied dead reckoning tracer?

But plotting itself requires reasonably accurate ranges, right?
Did they get those from telemeter tables? Or was there some other way still?

And for the fixed wire, they did use U-Jagd, right?

I remember reading somewhere that they had tables, listing the linear, rather than angular, torpedo parallax, which allowed shooting at any angle without knowing range to the target, using the target length as a rough yardstick.

Originally Posted by Pisces

This particular statement: Yes, the speed computation is fictitious. I just came up with the idea of abusing the scales for that computation while OneLifeCrissis was making his GUI. I worked out the magic number for getting the calculation to work on the scales. And asked him to include a scratch mark on it as if it was carved in by the commander with a knife. Since then this was copied in pretty much every mod, and for different games, that included the RAOBF function.

Oh, so you are the one who invented it?
Very interesting indeed. I think a lot of people now believe it is historical.

Do you know why the whole device was simulated in Silent Hunter the way it was then?
Why the tick counting, instead of linking it to the stadimeter, which is simulated already anyway?
Why are the two marks and the Kurswinkel ring fixed?

How did the real thing function in terms of scope magnification?
Did you have to divide everything by four in low power, like with the American stadimeter?

As you said yourself, this version was reproduced pretty much everywhere.
No pressure, of course, just wandering.

Originally Posted by Pisces

As for centi- or mili-radians, this is not limited to the metric system! This applies equally well to the imperial system. It is just that in the imperial system height is usually measured in feet, and length or distance in yards. So you need to include a conversion factor of 3 in it. Or start measuring height in yards as well. Considering 2000 yards is close to 1 nautical mile (good enough for government work) this is not such a bad idea.

Essentially, centi-radians (or milliradians) means you are talking about a slope of 1 over 100 distance (respectively 1 over 1000 distance). So if something is 3 milliradians then it is 3 yards (or 9 feet) high at 1000 yards distance. Similarly, if it is actually 27 yards high, you are 9000 yards distant from it.
The same can be done in metric as long as you maintain the same system for both height and distance. 30 meters high over 2000 yards does not result in 15 milliradians. (though you will be close to within 10% error. ballpark quality)

Yeah, I understand that mils work in any units, as long as those units are consistent. But because of the foot vs yard thing, it is just not as convenient, I suppose.
According to the American Fleet Submarine Torpedo Fire Control manual, those scopes are marked in degrees, not mils, as one degree is 50 feet at 1000 yards. A rough approximation, sure, but something you can compute in your head.

I guess it is a matter of whether you prefer to multiply by two or divide by three.

[derstosstrupp]

Originally Posted by Nikdunaev

Sorry, what exactly are the KTBs?
You are saying that the stadimeter and the adjustable stand scope never actually coexisted in one unit, is that right?

I am curious, why could they not, say, take the boat one or two meters deeper, and use the normal, full length scope, with the same effect of it sitting low? Especially in quiet weather, when scope is most visible, but depth control is also easier and more precise...

KTBs are the logbooks maintained on patrol. Correct, stadimeter did not exist on StaSr. To your second question, head of the attack scope was smaller, significantly so, and depth control is still difficult even at a slightly different depth. I’m not sure what the difference in heights was, if any at all. But depthkeeping was certainly difficult even a couple of meters deeper in rougher weather, and they would not have forgone the advantage of an adjustable fixed eye scope just for that anyway.

Originally Posted by Nikdunaev

Did they plot on the map? Maneuvering board? I assume they did not have a device similar in function to the allied dead reckoning tracer?

But plotting itself requires reasonably accurate ranges, right?
Did they get those from telemeter tables? Or was there some other way still?

Plotting was done on what was called millimeter paper, which is like graph paper on steroids. Very tiny squares that allow for accuracy. Now, there was no rangefinding device reliable on the surface, because the UZOjust was a bearing transmitter, but what they did to plot was they used the mast tips on the horizon as a reference. They knew if just a little bit of mast was showing, that might be 16 nautical miles or so, and they based their plot on whether those mast tips grew or shrank. Over time you can develop a very accurate plot. Note that this was only on the surface and only during the day; submerged, plotting like this was generally not done. The preferable method however on the surface was simply adjusting own course and speed until it appeared they were paralleling the target, that is the simplest way to get the target data (“Ausdampfen”). But no DRT or anything like that like the US. All done by the navigator, with information supplied either by the skipper or a watch officer.

Originally Posted by Nikdunaev

And for the fixed wire, they did use U-Jagd, right?

Probably not. U-Jagd means the hunting of subs, ASW. That watch was actually used by German ASW to plan depth charge approaches. Now, it just so happens that it is handy to use for this method, because the principles are the same, distance traveled over time. They had tables to help with this, but may have also used some form of stopwatch, there is reference made to that in at least one source.

Originally Posted by Nikdunaev

I remember reading somewhere that they had tables, listing the linear, rather than angular, torpedo parallax, which allowed shooting at any angle without knowing range to the target, using the target length as a rough yardstick.

Absolutely correct.

Originally Posted by Nikdunaev

How did the real thing function in terms of scope magnification?
Did you have to divide everything by four in low power, like with the American stadimeter?

The reticle was designed for 1.5x. In game you can multiply by 4 in 6x but IRL this was more complicated due to nuances in the optics. Rangefinding at 1.5x only was recommended.

[Nikdunaev]

Sorry for the late reply

Originally Posted by derstosstrupp

Plotting was done on what was called millimeter paper, which is like graph paper on steroids.

Simple millimeter paper and no proper rangefinding device? Sounds like a big "ouch" to me.

Originally Posted by derstosstrupp

Probably not. U-Jagd means the hunting of subs, ASW. That watch was actually used by German ASW to plan depth charge approaches. Now, it just so happens that it is handy to use for this method, because the principles are the same, distance traveled over time. They had tables to help with this, but may have also used some form of stopwatch, there is reference made to that in at least one source.

U-Jagd is not a purpose made tool? Oh...
I honestly thought it was designed for this specific purpose. Those scales look very much like reasonable ship lengths and speeds...

What is the use for depth charging purposes? What do the scales represent in that case?

I am no expert in German, but the name, does it not stand for "unterwasser jagd" or "unterseeboot jagd"? Submarine hunting. Does it actually say if the hunting in question is for or by the submarine itself? I am curious.

By this point I am afraid to ask further. Does the Silent Hunter community actually use any historical tool correctly?

Originally Posted by derstosstrupp

The reticle was designed for 1.5x. In game you can multiply by 4 in 6x but IRL this was more complicated due to nuances in the optics. Rangefinding at 1.5x only was recommended.

Was it any different from the US optics?
Cause for the latter, as far as I know, multiply or divide by four was the "officially endorsed" method in real life. Both for the stadimeter and the telemeter scales.

The optical zoom, does it not change the angular field of view by that factor? 4 times in our specific case?

[derstosstrupp]

Originally Posted by Nikdunaev

Sorry for the late reply



Simple millimeter paper and no proper rangefinding device? Sounds like a big "ouch" to me.





U-Jagd is not a purpose made tool? Oh...
I honestly thought it was designed for this specific purpose. Those scales look very much like reasonable ship lengths and speeds...

What is the use for depth charging purposes? What do the scales represent in that case?

I am no expert in German, but the name, does it not stand for "unterwasser jagd" or "unterseeboot jagd"? Submarine hunting. Does it actually say if the hunting in question is for or by the submarine itself? I am curious.

By this point I am afraid to ask further. Does the Silent Hunter community actually use any historical tool correctly?



Was it any different from the US optics?
Cause for the latter, as far as I know, multiply or divide by four was the "officially endorsed" method in real life. Both for the stadimeter and the telemeter scales.

The optical zoom, does it not change the angular field of view by that factor? 4 times in our specific case?

Correct, U-Jagd was the term used for hunting of subs, not by. We have the service manual for German ASW as part of the Crush Depth project (in my sig). The word “Annäherung” means “closure” - it’s for timing closure rate most likely, probably to assist in depth charge pursuits. The concept is the same though, distance in m converted to knots.

To your question about there being anything realistic used by the community, yes, these concepts are all historical, it’s just sometimes the devices that are used to get there are a little different than what they actually used. The recognition manual is overused though, that didn’t have that kind of data that these games have, so that’s probably the biggest diversion. And using the manual assumes that the very good vision we have out of the periscopes in game was how it was, and it certainly was not. Viewing a target with the head of a periscope just at the waterline, with fogging, and waves etc. was apparently very difficult. Hence the emphasis on gathering data on the surface while overtaking.

Multiplied by four is correct for 6x, however, there was something with the optics that made that not so straightforward. To the extent that the commander’s handbook recommends rangefinding only at low power.

I can answer the second part of your question to Pisces, only because I know the answer at the ready about the multiple oculars. So the one on the left, with the wire going out of it, inside of that one there was apparently a depiction of the torpedo triangle in colors. This allowed the user to visualize the lead angle. It was linked, at least by my understanding, to the AOB finder, since AOB is an angle in the torpedo triangle (gamma). The only other critical pieces of information are target and torpedo speed, and I’m not clear on how those were entered exactly. The ocular on the top inside of the RAOBF I believe was how the prisms were viewed for the stadimeter.

These sound like great features, and they are very innovative, but with the TDC it’s easy to see how they are somewhat superfluous.

[diego_gut]

"Multiplied by four is correct for 6x, however, there was something with the optics that made that not so straightforward. To the extent that the commander’s handbook recommends rangefinding only at low power."


The zoom and field of view had different ratios, perhaps that made it impossible to calibrate the graticle for both.

[Nikdunaev]

Originally Posted by diego_gut

The zoom and field of view had different ratios, perhaps that made it impossible to calibrate the graticle for both.

Sorry, I am not sure I understand what you are saying

The optical magnification in telescopes is increasing the apparent angular size of an object by a certain factor, compared to what would be seen by the naked eye.
The decrease in field of view, looking through the same eyepiece, is a direct consequence of that, right?

So, it seems that zoom and field of view are proportionally linked to each other by definition.
If not, than the magnification power number is just meaningless.

[diego_gut]

Originally Posted by Nikdunaev

Sorry, I am not sure I understand what you are saying

The optical magnification in telescopes is increasing the apparent angular size of an object by a certain factor, compared to what would be seen by the naked eye.
The decrease in field of view, looking through the same eyepiece, is a direct consequence of that, right?

So, it seems that zoom and field of view are proportionally linked to each other by definition.
If not, than the magnification power number is just meaningless.

In Sh3 it works like you say, there is a direct and inverse relationship between zoom and field of view. However, it is not like that in real life, it depends on the construction of the optical device.


In this particular case, the zoom ratio was 4 ( 1.5 to 6 ) but the field of view ratio was 4.22 ( 38 to 9 ). Since the graticle is just a 2d overlay it can't be accurate for both.


To give more examples, the field of view for the 7x50 binoculars was 7.1 but some 10x80 binoculars had a field of view of 7.25 even though they had 10x zoom. The field of view was different even between different models of the 10x80 binoculars.


What I did for DGUI was to use a 36 degree field of view for the low power, this way the periscopes can be calibrated at both magnifications. This is not historically accurate but I think it is more useful.


Regards

[Nikdunaev]

Originally Posted by derstosstrupp

Crush Depth project (in my sig).

That one looks really amazing...

A highly detailed and accurate, historically and physically, submarine simulation, representing the actual particulars of the boat, as they functioned in real life?
Yes, please!

Originally Posted by derstosstrupp

I can answer the second part of your question to Pisces, only because I know the answer at the ready about the multiple oculars. So the one on the left, with the wire going out of it, inside of that one there was apparently a depiction of the torpedo triangle in colors. This allowed the user to visualize the lead angle. It was linked, at least by my understanding, to the AOB finder, since AOB is an angle in the torpedo triangle (gamma). The only other critical pieces of information are target and torpedo speed, and I’m not clear on how those were entered exactly. The ocular on the top inside of the RAOBF I believe was how the prisms were viewed for the stadimeter.

Visualize the lead angle? How was it different from setting the lead angle on top of the bearing ring on the scope tube? The one visible in the "bubble" when looking through the scope?

Or was it automated, with TDC-like functionality?

So, the stadimeter prisms were only visible through one eyepiece, but not through the other, is that right?

Why not just align the ghost image, or move it all the way out of sight, when not being used?

In the scope photo on the first page, the ring sits on the bottom ocular, whereas on the photo above, it sits on the top. Otherwise they seem to be pretty much identical. Is there any significance to that, in terms of functionality?

Originally Posted by Nikdunaev

Originally Posted by Nikdunaev

[Pisces]

@derstosstrupp and Nikdunaev:

You are both talking about this image?
http://www.tvre.org/images/02_fot_07.jpg

[Nikdunaev]

Originally Posted by Pisces

@derstosstrupp and Nikundeav:

You are both talking about this image?
http://www.tvre.org/images/02_fot_07.jpg

Yes, exactly

[Hitman]

Ignore the film footage, those were overlays added on post-production to the film. When you looked through teh scope the reticles were noting like what you see in Youtube or Das Boot.

[John Pancoast]

Originally Posted by Hitman

Ignore the film footage, those were overlays added on post-production to the film. When you looked through teh scope the reticles were noting like what you see in Youtube or Das Boot.

I was wondering if you'd chime in. Hope all is well.

[Hitman]

Yes John all is OK thanks God

I check daily here but I don't usually have much time to read or reply.

[John Pancoast]

Originally Posted by Hitman

Yes John all is OK thanks God

I check daily here but I don't usually have much time to read or reply.

[derstosstrupp]

Hitman is the reason I ventured down the path of wanting to learn more - his research back 10 years ago or so was what got me initially curious. Thanks Hitman!