Sextant by MR - Charis
Sextant by MR - Charis
Sextant by MR - Charis
PREPARED BY:
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Physics Lab Observation Sheet SEXTANT 2009-2010
Exp. No: SEXTANT
Date:
X
Formula: The height of the ceiling is given by H = h '+ m.
cot β − cot α
where α and β are the angles subtended by the top at two different positions of sextant a distance X
apart and h’ is the height of the reference point from the ground.
Figure: Ray from Ceiling
M1
Mirror
Main Scale
SEXTANT
Procedure:
1) Adjust all the scales on the sextant to read ZERO.
2) Draw a reference line on the wall using pencil and scale at the level of eye.
3) Using measuring tap mark four points on the floor at a distance of 1m, 2m 3m & 4m.
4) The sextant is taken closer to the reference point by observing through the telescope.
5) Observing through the telescope, adjust the mirror M1 such that the reference line comes in the field
of view from the mirror M2, such that the reference line in the two halves of the mirror M2 is
coinciding.
6) Now move the sextant through one meter distance and rotate the movable arm gradually such that the
reference line in the two halves of the mirror M2 is coinciding. Note the reading of the sextant. This is
called Zero Error Reading.
7) Movable arm is rotated gradually till the reference line and the image of the upper mark of the ceiling
whose height is to be determined, in the two halves of the mirror M2 is coinciding. Note the reading
at this position. This is the Elevation Reading.
8) The difference between the Elevation Reading and the Zero Error reading gives the Angle of
elevation.
9) Repeat the steps 6, 7 & 8 by moving the sextant through 2m, 3m & 4m distance from the wall.
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Physics Lab Observation Sheet SEXTANT 2009-2010
Tabular: Determination of Angle of Elevation
Sextant Readings
Zero Error Readings Elevation Readings Angle of
S.
Distance Elevation
No
M.S.R C.S.R V.S.R Total ‘X’ M.S.R C.S.R V.S.R Total ‘Y’ Y-X
1. 1m α=
2. 2m β1 =
3. 3m β2 =
4. 4m β3 =
Calculations:
1) d1 = 1 meter α = ___________ β1 = ___________
d1
h1 = m = ____________ .
cot β1 − cot α
d2
h2 = m = ____________ .
cot β 2 − cot α
d3
h3 = m = ____________ .
cot β3 − cot α
h1 + h2 + h3
Mean h = = ____________ m.
3
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Physics Lab Observation Sheet SEXTANT 2009-2010
Percentage error:
Standard value of the height of the ceiling, hStandard = ________m.
Precautions:
1) The zero reading changes from one distance to another distance. So every measurement of elevation
angle, zero reading should be determined separately.
2) The two mirrors M1 and M2 must be made parallel to each other and perpendicular to the plane of
arc with the help of screws.
3) The reference mark and the different distances of observation should be in a straight line.
4) While taking the observations, two images must be overlapped properly.
Result:
The height of the ceiling, h = ________meter with _________ error.
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