Which are two main points important for an astronomical telescope?

The focal length of the objective and eyepiece of a telescope are respectively $200 \, cm$ and $5 \, cm$. The maximum magnifying power of the telescope will be

The magnifying power of a telescope is $9.$ When it is adjusted for parallel rays,the distance between the objective and eyepiece is $20\; cm.$ The focal lengths of the lenses are:

$A$ giant refracting telescope at an observatory has an objective lens of focal length $15 \, m$. If an eyepiece of focal length $1.0 \, cm$ is used,what is the angular magnification of the telescope?

$A$ Cassegrain telescope uses two mirrors of radii of curvature $25 \ cm$ and $16 \ cm$ separated by a distance of $2.5 \ cm$. The position of the final image of an object at infinity is

An astronomical telescope of ten-fold angular magnification has a length of $44\, cm$. The focal length of the objective is.......$cm$