if second reading is more than first, it represents a rise

if first reading is more than second, it represents a rise

if first reading is less than second, it represents a fall

both if first reading is more than second, it represents a rise and if first reading is less than second, it represents a fall

in astronomical telescope, the rays from the object after refraction at the objective are brought to a focus before entering the eyepiece to produce a real inverted image in front of the eye piece

in Galileo's telescope, the rays from the object get refracted at the objective and are intercepted by the eyepiece before a real image is formed

a line passing through the optical centre of the objective traversing through the eyepiece, is called line of sight

All of these

balancing the sights

balancing the departures

balancing the latitudes

balancing the traverse.

saving of time is a main factor

better accuracy is a main factor

given points are inaccessible

none of these.

is always taken on a point of known elevation or can be computed

is added to the known level to obtain the instrument height

taken on an inverted staff is treated as negative

all the above.