If α is the observed altitude, the refraction correction in seconds, is
58 cot α
58 tan α
58 sin α
58 cos α
Correct Answer :
A. 58 cot α
Related Questions
The altitudes of a circumpolar star at culminations are 70° and 10°, both culminations being north of zenith. The declination of the star, is
80°
70°
60°
50°
Homologous points are
Opposite corners of a photograph
Nodal points of the camera lens
Corresponding points on the ground and photograph
Plumb points of stereo pair of photographs
The latitude (λ) of a place and the altitude (α) of the pole are related by
λ = α
λ = 90° - α
λ = α - 90°
λ = 180° - α
The length of a parallel of λ latitude between two meridians is equal to difference in longitudes multiplied by
sin λ
cos λ
tan λ
cot λ
Longitudes are measured from 0° to
180° eastward
180° westward
180° east or westward
360° eastward
In a spherical triangle ABC right angled at C, sin b equals to
sin c sin B
cos c cos B
tan c tan B
sin c cos B
The difference in longitude of two places expressed in time is equal to the difference in their
Sidereal time
Apparent solar time
Mean solar time
All the above
The relation between the air base (B), photographic base (b), flying height (H) and the focal length (f) of a vertical photograph, is
B = bH/f
B =f/bH
B = b/fH
B = H/bf
The great circle whose plane is perpendicular to the axis of rotation of the earth, is called
Equator
Terrestrial equator
0° latitude
All the above
The zenith is the point on the celestial sphere
East of observer
West of observer
North of observer
South of observer
Pick up the in-correct statement from the following:
Apparent solar time is measured from the lower transit of the true sun
Mean solar time is measured from the lower transit of the mean sun
Sidereal time is measured from the lower transit of the first point of Aries
Sidereal time is measured from the upper transit of the first point of Aries
At the first point of Aeries, the sun moves
Northward
Southward
From south to north of the equator
From north to south of the equator
The correction for parallax, is
- 8.8 cos α
+ .8 sin α
+ 8.8 cos α
- 8.8 cos α
The relief displacement of a building 72 m high on photograph is 7.2 mm and its top appears 10 cm away from principal point. The flying height of the camera, is
500 m
1000 m
1500 m
2000 m
The orthogonal projection of the perspective centre on a tilted photograph, is called
Nadir
Isocenter
Principal point
Plumb point
The great circle along which the sun appears to trace on the celestial sphere with earth as centre during the year, is called
Equator
Celestial equator
Ecliptic
None of these
The altitude of a heavenly body is its angular distance, measured on the vertical circle passing through the body, above
Equator
Horizon
Pole
None of these
The declination and right ascension of the sun becomes 23° 27' S and 270° respectively on
March 21
June 21
September 21
December 22
The scale of a tilted photograph of focal length f, taken from an altitude H, along the plate parallel through plumb point, is
f/H sec θ
f sec θ/H
f/H
f/H cos ½θ
The Polaris remains below horizon at
10° N
50° N Latitude
Equator
5° S latitude
The normal longitudinal overlap is generally kept
50 %
60 %
70 %
75 %
In a spherical triangle ABC, right angled at C, sin b equals
sin a cos A
cos a sin A
tan a cot A
cot A tan a
Stellar astronomy deals with
Plane surveying
Geodetic surveying
Star observations
Planet observations
The circle in which a plane tangent to the earth's surface at the point of observation, intersects the celestial sphere, is called
Visible horizon
Sensible horizon
Celestial horizon
True horizon
If f is the focal length of the camera lens and θ is the angle of tilt, the distance of the plumb point from the principal point will be
f sin θ
f cos θ
f tan θ
f sec θ
From the principal point the horizon point lies on the principal line at a distance of
f tan θ
f sin θ
f cot θ
f cos θ
In a truly vertical photograph,
Principal point coincides the isocenter
Iso-centre coincides the plumb point
Plumb point coincides the principal point
All the above
In field astronomy, the quantities observed are entirely
Lengths
Angles
Heights
All of these
The height displacement on a vertical photograph
Increases as the horizontal distance increases from the principal point
Increases as the ground elevation increases
Decreases as the flying height increases
All the above
The plane at right angle to the zenith-nadir line and passing through the centre of the earth, is called
Rational horizon
True horizon
Celestial horizon
All the above