Focal length of objective and eye piece of telescope are $200 \; cm$ and $4 \; cm$ respectively. What is the length of telescope for normal adjustment (in $; cm$)?

$A$ lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since :

If the tube length of an astronomical telescope is $105 \, cm$ and the magnifying power is $20$ for normal setting,calculate the focal length of the objective in $cm$.

In an astronomical telescope,the focal lengths of two lenses are $180 \, cm$ and $6 \, cm$ respectively. In normal adjustment,the magnifying power will be

$A$ telescope has an eyepiece of focal length $5\, cm$ and an objective lens of focal length $60\, cm$. It is focused on a distant object such that the rays emerge from the eyepiece as parallel rays. Find the angular width of the image in degrees $(^o)$ if the object subtends an angle of $2^o$ at the objective.

The focal length of the objective of an astronomical telescope is $1.5 \ m$. Under normal adjustment,the length of the telescope is $1.56 \ m$. The focal length of the eyepiece is: (in $m$)