U-Boot Periscope Telemeters
 

Hi Everyone!

I noticed that in Silent Hunter the telemeters on German periscopes seem to be marked in degrees just like the American ones.
At least, the scale seems to match the Stadimeter reading in degrees, and a manual calculation, assuming the ticks are degrees, gives good range.

At the same time, some other sims, like, say, Wolfpack, seem to have those scales in centiradians. That means, on low magnification, number 10 corresponds to 5.7 degrees.
This actually makes a lot of sense for metric units, as then the calculation of range in hectometers becomes super easy indeed.

Further, historical things, like RAOBF, seem to function in centiradians.

So, my question is, which scale is historically accurate?
Are there any mods producing the correct scale in Silent Hunter?

Also, what are the correct magnification powers for the periscopes?
I thought they should both be 1.5X and 6X. Yet in Silent Hunter the observation scope shows 1 and 4. Is this actually the case? Or is it just a typo on the indicator?

Real ones were in milliradians on the vertical, degrees on the horizontal. Both attack scope (at least the C/2 Stand-Sehrohr, the one you sit at and operate with pedals in the tower) and the control room “observation” scope were 1.5x and 6x. The sight picture through the attack scope can be seen here, drawing 17:

http://www.tvre.org/en/aiming-with-the-periscope

Hitman’s optics are imo the best representation of historical scopes.

Additionally, that scope model (C/2) did not have a stadimeter or RAOBF, 2 features present in earlier attack scope models but which were dropped in favor of better optical quality. Mostly data was gathered on the surface (by matching or rough plotting), and range was largely irrelevant due to the fact they shot at low gyro angles.

Thank you for your reply! That is a lot of interesting information!

What is the use of having the horizontal scale in degrees?

Also I kinda understand the case against the stadimeter... But the RAOBF ring was just sitting around the eyepiece, right? What does that have to do with optical quality?

I remember seeing the kinds of scopes, like the ones shown in the article, in one of the mod packs, for Silent Hunter V.
Just curious, is there an actual photo showing the view?

Though I was originally referring to the ones that look more like what we have in stock Silent Hunter and Wolfpack, this kind:

https://i.pinimg.com/originals/0d/16...a12f5ff03e.jpg

Is that a different model or manufacturer? Perhaps, an earlier-war or pre-war version?

Do those scales look like centiradians? I am not too sure... Notice the lack of degree signes next to the numbers. Unlike what was shown in the drawings.

Hitman's mod, from what screenshots I found, uses both types. The night scope is similar to the article drawings, and, at the same time, the attack scope is similar to the photo.

https://i.imgur.com/WOF6qxb_d.jpg?ma...idelity=medium

https://i.imgur.com/biEXHnH_d.jpg?ma...idelity=medium

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.

So RAOBF was a mechanically integral part of the stadimeter? Wow.
I never knew that bit. Always thought it was just a calculator, akin to the American calculators, such as the Omnimeter, the hand held slide ruler.
Now, that I am looking closely at the real life pictures, the thing does not even have the Optische Länge scale that all the mods in the sim have. So no way to use it manually...

Does that mean features like speed computation are entirely fictitious?

And it took me a while to realize the original German name was not RAOBF...
Stupid me :k_confused:

ASR C/6 has it:

http://www.tvre.org/images/02_fot_08.jpg

This is actually very confusing. Is C/6 not a Later-war model? The first article mentioned it was meant for the Typ XXIII.
At the same time it is clearly not a stand-scope.
By the way, why the two separate eyepieces?

The C/2, what year was it introduced?
Did the early-war boats have something else as their turm scope?
Was there some other mod of the StaSR? Logic suggests there should be a C/1 somewhere. :)

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.

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.

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.

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)

I believe the word was actually "doohickeyachnachsingzig" :D

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. :D
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.

Didn't know there were E in Roman numerals. ;)

Fat fingers. :)

:haha::har::Kaleun_Applaud:

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...

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.

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

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. :)

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. :)

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.

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.

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.

Absolutely correct.

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.