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    Re: Sundial
    From: Gary LaPook
    Date: 2016 Apr 30, 18:20 +0000
    It's an M-2 aiming circle and is used to "lay the battery" to align all the fire control panoramic telescopes on each of the guns so that they are set on the "azimuth of fire." I did some computations and set the index on the aiming circle to the resultant which aligned the "0" line of my aiming circle on the chosen azimuth of fire, chosen  so that the guns would deliver fire into the area where the battle was being fought. This means that when I set my aiming circle to "0" mils and looked through my sight that I was looking in the direction of the azimuth of fire. 
    The panoramic telescope mounted on each cannon is similar to my aiming circle except that they are mounted so that the "3200 mil line" is parallel with the gun's bore so that when the gunner on the cannon set his pantel to "3200" that he was looking in the direction that the shells would be flying. 
    So the procedure was this. I would go forward to the new chosen firing position with my advanced party of gun guides at a grid that would allow the enemy to be within range of my guns, 22,600 meters, 14 miles, and set up my aiming circle. About a half hour later the rest of the artillery battery of four, eight inch howitzers would arrive and the guns would be guided into their positions (eighty meters apart extending 240 meters from left to right) by compass by the gun guides so that they were approximately aligned on the azimuth of fire. I then measured the azimuth to the pantel lens on the gun, say 2850 mils. The gunner on that gun would set his pantel scale to the same value, 2850, and then traverse his gun until he was looking at the lens of my aiming circle. Since his pantel was mounted so that his scale was rotated one-half circle from mine, 180 degrees, 3200 mils, this then made his 3200 line parallel with my zero line so it was aligned on the azimuth of fire and so was the bore line of his cannon. One complication was resulted from the fact that the pantel couldn't be mounted exactly on the bore line of the gun but was mounted about a meter off to the left of the bore line so when the gunner traversed his gun the pantel lens moved slightly so I had to measure another azimuth and the gunner would set in that new azimuth and traverse again. It usually took three or four iterations of this process until no further changes in azimuth occurred. I was doing this with all four of my guns, alternating between them. The standard was to have all four guns laid parallel on the azimuth of fire within three minutes of the first gun moving into position. Then when we had to fire the azimuth to point the guns was computed by the fire direction center and the "deflection" was sent to the guns where the gunners placed this reading on the pantel and then traversed the gun until he was looking at his collimator which then pointed the guns in the direction of the trfget. it was a little more involved than this but that explains how the M-2 aiming circle was used. 

    Maybe of more interest to this group is how I aligned my aiming circle in the first place. There were four ways to do this. The least accurate was to use the compass built into the aiming circle and it was done this way only if the more accurate methods were not available. The most common way was to sight on an aiming stake that had been put in position previously by a team of surveyors. The surveyors would place a stake in the ground over which I would place my aiming circle and then another stake about 200 meters away and measure that azimuth to that other stake and then leave  a tag on my stake with the azimuth to that other stake.

    During the day I could measure the azimuth to the sun, calculate its azimuth and then use this to set up my aiming circle. At night I would sight on Polaris and then on Kochab and then a table based on latitude and the difference between the azimuths would give me the accurate azimuth of Polaris which I would then use to set up my aiming circle. 

    There, now, aren't you sorry you asked?

    gl


    From: John D. Howard <NoReply_Howard@fer3.com>
    To: garylapook---.net
    Sent: Saturd
    ay, April 30, 2016 10:13 AM
    Subject: [NavList] Re: Sundial

    Gary, 
    Very nice sundial.  I am always impressed at the great varitey of designes.
    Is the device on the tripod a gun site for an artilery piece?  Looks like the sight for a 155mm Long Tom.
    John H.


       
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