How use graduations of the periscope ?

[lumat83]

Hi all :)

I would to like to know how calculate a fire solution with the périscope, without markers on the map (I know make this).

Exactly, how calculate the distance and the speed of a contact by use only the vertical and horizontal graduations of the periscope. I think that is possible but I don't undestand how.

Thank for your help :)

[Chock]

One thing you can do is time how long it takes the target to pass a mark on your periscope while you hold it still, if you ID the ship, you'll know its length, so you'll know how long it is taking in seconds for the target to travel a distance equivalent to the ship's length. From this, you could work out the speed.

I personally don't use this method, but I know some people do.

[lumat83]

Ok, thank Chock :)

But when I id a target, I know his lenght, the distance (with stadimeter) and the number of seconds the target travel between two marks, how calculate his speed ? :oops:

[Hitman]

Speed is distance divided by time. So you divide the length in meters by the number of seconds and get a speed measurement in meters per second. Usually multiplying by 2 the result gives you a reasonably aproximation to the ship's speed.

For example, a 100 metres long ships takes 20 seconds to entirely cross the vertical central line of your scope (You should point your bow to the enemy ship or be stationary to prevent the distortion of the results caused by your own speed), so you know it is travelling at 100/20 = 5 metres per second. Multiply by 2 that number 5, and you have an approximate speed of 10 knots.

The primary use of the lines was normally to determine mast heigth and thus the range, but you can also use it to calculate the AOB. Do a search in this forum for a thread opened by me posting a tutorial about manual targeting:up:

[lumat83]

Ok, thank for your great help :D

But the number of seconds the contact take to entirely cross the vertical central line of the scope depend to the distance between the contact and the submarine (It's not the same time if the contact is at 2000 m or at 500 m), and to the magnification of the scope, no ?

Also, where find the lenght of a ship (This is not on the recognition manual)