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(28-07-2021) T139/T140 Telescopic Sight - Wrong Magnification & Field of View


Tanks affected

  • T28
  • T95

 

Bug

Wrong telescopic sight magnification and field of view

 

Bug description

The T28/T95 in game is depicted as having 8.0x magnification with a FoV of 9. This sight configuration is wrong.

Pk8MO3S.jpg

 

AFV Technical Situation Report described the direct telescopic sight development for the T95 as follows:

March 1945

Telescope T139 and T140 are being designed for the Heavy Tank T28 / Gun Motor Carriage T95.

Both sights have the eye-piece assembly turned through 90° to the axis of the telescope, and being offset by 6 in (T139) and 3 in (T140).

CYGwVep.jpg

 

May 1945

After further study, it's decided to proceed only with the Telescope T140 with an eye-piece offset of 3 in (7.62 cm).

Therefore, terminating the Telescope T139 with an eye-piece offset of 6 in (15.24 cm).

9jOwhu2.jpg

 

May 1945 cont.

The proposed fire control equipment for the Gun Motor Carriage T95 includes one Telescope Mount T138 fitted with bore sighting adjustments to carry Telescope T140 (x3 magnification with eye-piece offset of 3 in).

7dWmlO8.jpg

 

August 1945

Nearing the completion of the first T95 pilot vehicle, some difficulties have been encountered in the optical design of the T140 Telescope.

The pilot vehicle will be initially equipped with the T139 Telescope with eye-piece offset of 6 in while the work on the T140 Telescope continues.

XIPlWGA.jpg

 

The exact FoV of this telescope is unconfirmed, but Monthly Letter to the War Office suggested that the auxiliary telescope was 70 in (1.77 m) long, and gave a 22° real field of view with a magnification of 3, referring to the the T140 telescope.

uUjx0n4.jpg

 

Trends in Development also specified that the telescopic sight of the T95 had 3 power magnification.

(The model name could be a typo, since the M8A1 was actually a name given to one of the periscopic sights used by the T95. The proper model name of this sight should be either the T139 or T140.)

vj4qZGQ.png

 

Bug fix

  • Change the telescope magnification from 8x to 3x
  • Change the telescope field of view from 9 to 22

 

Sources

Primary Sources:

  • Army Ground Forces Development Section - Trends in Development, 1947
Spoiler

UHRi0qX.png

  • British Army Staff – Royal Armored Corps (AFV) Technical Situation Report No. 34, 1945
Spoiler

a1hcxdH.jpg

  • British Army Staff – Royal Artillery Monthly Letter to the War Office, 1945
Spoiler

QKM2UCT.jpg

 

Edited by Sirchby
Additional sources
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  • Sirchby changed the title to T139/T140 Telescopic Sight - Wrong Magnification & Field of View
  • 5 months later...

The report has been submitted.

For any questions feel free to PM me or any other technical moderator.

Thanks for your time and effort

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  • LordMustang changed the title to (28-07-2021) T139/T140 Telescopic Sight - Wrong Magnification & Field of View
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