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angle of sight


sabine72
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I just purchased a "angle of sight instrument" and now i was wondering for what it was used ? The markings are Angle of sight instrument H.A.MK 1 J.H.STEWARD Ltd 1915

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Hi there,

If you download any of the "Machine Gunner's Handbooks", they give you a good description of how to use them in relation to Machine Guns; however, the principles are going to be the same for artillery if that is what you are interested in.

Go to the manuals page on www.vickersmachinegun.org.uk and download if you want.

Hope this is of use.

Rich

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Rich,

Thank you,

this is something for the husband, I'm not realy in to guns.

kind regards

sabine

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Sabine

I hope this helps ?

Angle of Sight. The angle of sight (A/S) is the vertical angle measured from the horizontal plane passing the the weapon to the (LOS) line of sight. It is described as elevation (or + or positive) if the target is above the gun, and as depretion (or – or negative) if the target is below the gun. The A/S compensates for the difference in altitude between the gun and the target. It is the last bubble to be levelled in laying the gun

John

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John,

Thank you, to me it is all latin, the husband should know what you mean, I would have been a verry lousy soldier :lol:

kind regards

sabine

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H'mm. Steward was still in business in the 1960s if not 1970s. The first question is whether this was an official instrument or one of Steward's many private venture products. The "H.A. MK 1" gives it a bit of officialese. We can play guessing games about HA but my first one is 'Heavy Artillery', problem is this doesn't make a lot of sense, so it could be something else.

The name implies that it was used to measure the vertical angle to something, this would mean it has some sort of eyepiece or an open sight that could be adjusted relative to the body that has a levelling bubble. There was an instrument like this in use until quite recently (and perhaps still) it was used by recce officers in short range air defence missile batteries to measure the local crests when selecting a launcher position, somehow I don't think this was a problem in WW1! IIRC this instrument was called an 'Abney Level' and since they came in a small leather pouch (about 4x2x2 inches IIRC) they clearly predated WW2.

However, there isn't much point in measuring angle of sight for artillery because local crests were the responsibility of the gun's Number 1 (possibly sect comd) and were measured by the simple expedient of looking through the barrel, levelling the sight clinometer and taking a reading. By 1915 artillery had finally got the message of deploying where they couldn't see their target. They weren't really any use to observers either since an angle of sight from the observer to the target isn't much use to anyone. However, one possible exception, measuring the height of burst of a shrapnel shell as an angle then using the distance to convert it to a height of burst (simple mental arithmetic using subtension). However, it's possible that they were used by surveyors to measure vertical angles if their theodolite or director was unable to measure vertical angles, and some didn't.

Angle of sight was set on the gun using the 'Sight Clinometer' that fitted into the sight mount (it also layed the gun in elevation), UK had a standard pattern, albeit with several marks, that remained in use into the 1980s if not 90s. Its distinguished by a spring clip underneath either end. The other type of clino was the 'Field Clinometer' which is considerably larger and was merely rested on a plane surface while laying. Americans have difficulty saying 'clinometer' so they renamed 'field clino' as 'Gunner's Quadrant', I assume UK machine gunners used the term clinometer, unless they too found it too challenging. ;-)

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Here are some pictures

two other one's

post-13594-1210095552.jpg

post-13594-1210095561.jpg

post-13594-1210095614.jpg

post-13594-1210095621.jpg

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Angle of sight was set on the gun using the 'Sight Clinometer' that fitted into the sight mount (it also layed the gun in elevation), UK had a standard pattern, albeit with several marks, that remained in use into the 1980s if not 90s. Its distinguished by a spring clip underneath either end. The other type of clino was the 'Field Clinometer' which is considerably larger and was merely rested on a plane surface while laying. Americans have difficulty saying 'clinometer' so they renamed 'field clino' as 'Gunner's Quadrant', I assume UK machine gunners used the term clinometer, unless they too found it too challenging. ;-)

British Army infantry continue to use the Field Clinometer (as described by you) for 'sight testing' (adjusting accuracy) of the C2 Quadrant Sight on the 81 mm Mortar, eight of which are used to support all battalions.

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That's a very odd device and definitely not an Abney level, but it seems to have an Ordnance arrow so it must be official. You wouldn't expect an angle of sight instrument to be graduated much more the 20 degrees and more likely half that and not above 90 degrees! If I've read it right its showing a 220 degree mark, which is a very odd angle of sight.

It doesn't seem to have any means of setting the angle only of measuring it, I assume the bit at the top is a clamp. This being the case then you place it on an inclined surface, let it settle, clamp it and read the scale. Survey seems the most obvious use if I've misread the range of angles, perhaps for tunnelling but the name doesn't seem right for that.

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Might be 220 minutes.

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Might be 220 minutes.

As far as I'm aware it was always degrees and minutes. It's difficult to judge the actual angle, and the scale may be under magnifying lens, but the graduations don't seem to support that level of precision.

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