The UZO markings in my experience are inaccurate. There is a good mod on this forum which improves upon this. It also changes UZO to 6x.
https://www.subsim.com/radioroom/sho...d.php?t=165408
Still even with that mod I find that it is easy to make mistakes with UZO range. Especially at night it becomes more challenging. The WO is good crosscheck to your calculations, as he gives the range to closest target when you ask.
Then a good alternate are the crude values at what range a ship fills your UZO/periscope, so you can forget about the ticks. In TWOS there is a table for it, but here are some numbers. Not perfect, but you can test them to see how they hold up.
1. Position so that a ship's length fills the FOV of your UZO/PER.
2. Choose the closest ship length or interpolate.
3. Choose the correct column UZO/6x/1,5x.
4. Result is range in meters.
Ship / length / UZO / 6x / 1,5x
LINER / 220 / 2000 / 1800 / 500
LMER / 180 / 1600 / 1500 / 450
TANK / 160 / 1500 / 1200 / 400
MMER / 100 / 900 / 800 / 200
SMER / 75 / 700 / 600 / 120
BOAT / 25 / 200 / 160 / 40
If the ship aspect is outside AOB90, divide the above by this.
AOB 60 1,13x
///// 45 1,42x
///// 30 2x