TDC

[CapnScurvy]

Snakedocpl, I believe your images of the Stabilized Azimuth Line are a bit misleading. The line could be placed anywhere within the periscopes Field of View. It was independent from the Telemeter Divisions........ so it was not "centered" to the FoV. You focused the line (bringing it in sharper), placing it just ahead of the targets bow, then turned the clutch "in" to engage the synchronous motor (which would have already been plugged in) just as the targets bow touched the line. Using a stop watch, you time the passage of the target. Unlike the images, there are no graduated marks, or scale for the Stabilized Line......just a line.

I'm not nit picking your help, just don't want to mislead anyone.

Originally Posted by Snakedocpl

The stabilized line compensated only change of periscope bearing and change of submarine course. It could do nothing with the speed. To make the target speed most accurate, the speed of own submarine should be relatively small.

The estimated target Speed is calculated by knowing the estimated length of the target, and how long the target takes to pass the Stabilized Azimuth Line. That's why the stop watch is used. Estamated Speed was found.

Originally Posted by Snakedocpl

Looking at this manual (http://www.maritime.org/doc/pdf/tbt.pdf), it seems, that TBT was not fitted in "stabilized line in space".

That's correct. The TBT has only the permanent "cross hairs" as shown. Which by the way were "illuminated" for night use.....when plugged in.

[snakedocpl]

Originally Posted by CapnScurvy

Snakedocpl, I believe your images of the Stabilized Azimuth Line are a bit misleading. The line could be placed anywhere within the periscopes Field of View. It was independent from the Telemeter Divisions........ so it was not "centered" to the FoV. You focused the line (bringing it in sharper), placing it just ahead of the targets bow, then turned the clutch "in" to engage the synchronous motor (which would have already been plugged in) just as the targets bow touched the line. Using a stop watch, you time the passage of the target. Unlike the images, there are no graduated marks, or scale for the Stabilized Line......just a line.

These images are my impression, because I have never look through the periscope with stabilized line. The impression based on the construction drawing of the ocular box. I marked stabilized line with red color. Of course it can be moved through the view (after decoupling from motor). The first drawing presents it after placing it at the bow of the target. On the second drawing the scope was rotated, but line stays at the same place as before (rotated by synchro-motor). That's why I wrote, that target is stationary. In reality, the target would move, and the line would be slightly shifted relative to the bow.

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Regards
Maciek