U-Boot Periscope Telemeters

[John Pancoast]

Originally Posted by derstosstrupp

The degrees in the horizontal were to be able to eyeball spread angles quickly.

Earlier attack scope models had the RAOBF rings around the ocular, but if you look at pictures of the fixed-eye attack scope (C/2), those rings don’t exist. What you have to understand about the RAOBF when it was implemented in the earlier scopes is that it was integrated with the stadimeter, such that when you turned the prisms, the rings turned automatically. So it was all one unit. After measuring the range vertically, the prisms were turned 90° and the same thing was done with the target length, and you had range and angle on bow as outputs on the rings. Both however being dependent on accurate target height and length, both of which cannot be (and weren’t) relied on in wartime.

Those scales with the tens are indeed in centiradians. Now, that’s a good question, that may in fact be a reticle of an early scope model. As for the attack scope one that I mentioned (C/2, the most common wartime one), I know that one for sure since I have access to the service manual for that periscope. The only doohickey it had on it was a true bearing counter. But overall, the tactical advantage of being able to raise and lower the scope by way of a lever while sitting in one spot was huge, because the skipper could keep the head of the scope right at the waterline at all times. So it was definitely a trade off, in more ways than just optical quality, I can’t quite remember all of the others.

The hitman optics I’m referring to though are the ones in his GUI, not his plain optics mod, which is what the above I think is from.

I believe the word was actually "doohickeyachnachsingzig"

[derstosstrupp]

Originally Posted by John Pancoast

I believe the word was actually "doohickeyachnachsingzig"

Haha indeed!

Truth is stranger than fiction in this case, in the manual it’s even wilder:
Zählwerk für rechtweisende Peilung

[John Pancoast]

Originally Posted by derstosstrupp

Haha indeed!

Truth is stranger than fiction in this case, in the manual it’s even wilder:
Zählwerk für rechtweisende Peilung

The real reason the Germans lost the war; by the time they got emergency orders typed up for the radio it was to late.
Same reason the Roman Empire fell; Rome was asked to repeat the message of how many Barbarians were at the gates ?
"Octavious you lout, I said CVIIXVCIIIIICCCCVVVXXXCVVVVIII ! No sorry, I meant VXXXIIIICICIVVVIIIIXXCEEVXCCVVXXCIIICCCIIXXCXCXCXI III ! Send help quick ! By the time they computed how many that was, to late.

[Pisces]

Didn't know there were E in Roman numerals.

[John Pancoast]

Originally Posted by Pisces

Didn't know there were E in Roman numerals.

Fat fingers.

[Nikdunaev]

Originally Posted by John Pancoast

The real reason the Germans lost the war; by the time they got emergency orders typed up for the radio it was to late.
Same reason the Roman Empire fell; Rome was asked to repeat the message of how many Barbarians were at the gates ?
"Octavious you lout, I said CVIIXVCIIIIICCCCVVVXXXCVVVVIII ! No sorry, I meant VXXXIIIICICIVVVIIIIXXCEEVXCCVVXXCIIICCCIIXXCXCXCXI III ! Send help quick ! By the time they computed how many that was, to late.

[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?

[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.

[Pisces]

Originally Posted by Nikdunaev

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

I am the one that invented the speed trick.
(from the old days: https://www.subsim.com/radioroom/sho...&postcount=135) And the other scratch mark just under 15 degrees, for magnification adjustment. If I was unclear, I am not the person that made the RAOBF mod. That was a collective effort of Hitman, JoeGrundman and OneLifeCrissis. They don't seem to be around here much. Unless they visit subfora that I don't visit.

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?

I have no clue what modding difficulties they encountered while trying to make this. My knowledge is skin deep. But I'm sure this was motivated by that. Lack of available resources in modifying the GUI to move the way he wanted it/work like the historical device. It must have been the best way to replicate it.

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?

Much of how it works can be learned on the following site. It is a gold mine if you want to know more about everything connected to target acquisition, tracking and torpedo guidance (from both sides of the war): http://tvre.org/en/ They have an English and a Polish language version.

Did you have to divide everything by four in low power, like with the American stadimeter?

As mentioned in my above first quote. The magnification trick uses the mark at 14.5-ish degrees. If you calculate the sine of that angle, you get 0.25. In other words, one quarter. If you line up the low-zoom size to the mark, you get the high-zoom size at the index at the top. For correction of the AOB width in low zoom it is a bit more complicated, and I actually forgot. Maybe you can find it in the archives if you search for my name in OLC's threads. The top link should be a start in the right direction.

https://www.subsim.com/radioroom/sho...&postcount=222
And finally: https://www.subsim.com/radioroom/sho...&postcount=263

!!! Be aware though, the precise values and steps relied on that older mod. For use in current RAOBF/GUI mods make sure to consult the documentation of the mod. It's scales may differ.

[Nikdunaev]

Originally Posted by Pisces

I am the one that invented the speed trick.
(from the old days: https://www.subsim.com/radioroom/sho...&postcount=135) And the other scratch mark just under 15 degrees, for magnification adjustment. If I was unclear, I am not the person that made the RAOBF mod. That was a collective effort of Hitman, JoeGrundman and OneLifeCrissis. They don't seem to be around here much. Unless they visit subfora that I don't visit.

I have no clue what modding difficulties they encountered while trying to make this. My knowledge is skin deep. But I'm sure this was motivated by that. Lack of available resources in modifying the GUI to move the way he wanted it/work like the historical device. It must have been the best way to replicate it.


Much of how it works can be learned on the following site. It is a gold mine if you want to know more about everything connected to target acquisition, tracking and torpedo guidance (from both sides of the war): http://tvre.org/en/ They have an English and a Polish language version.

As mentioned in my above first quote. The magnification trick uses the mark at 14.5-ish degrees. If you calculate the sine of that angle, you get 0.25. In other words, one quarter. If you line up the low-zoom size to the mark, you get the high-zoom size at the index at the top. For correction of the AOB width in low zoom it is a bit more complicated, and I actually forgot. Maybe you can find it in the archives if you search for my name in OLC's threads. The top link should be a start in the right direction.

https://www.subsim.com/radioroom/sho...&postcount=222
And finally: https://www.subsim.com/radioroom/sho...&postcount=263

!!! Be aware though, the precise values and steps relied on that older mod. For use in current RAOBF/GUI mods make sure to consult the documentation of the mod. It's scales may differ.

Thanks for all the links!

Actually, http://tvre.org/en/ is where I got most of my questions from.

The scope and ring pictures above are theirs.
That article mentions that the device could be used for either magnification in real life, but does not give any detail.
So, given that there is no Optische Länge scale on the thing, and the two pointers work differently as well, in real life... I started wondering how it was supposed to work.

Why the two different eyepieces on the scope?
Does this have anything to do with magnification?
Apparently the ring could be mounted on either:


Also what is the purpose of the big knob in the lower left corner of the ring? I can not find any references to that one in the text of the articles, even though it is numbered in one of the photos.