In which type of telescope,an extra pair of inverting lens is available?

What is the length of an astronomical telescope for normal adjustment?

In an astronomical telescope,the focal lengths of the objective lens and the eyepiece are $150 \, cm$ and $6 \, cm$ respectively. In the case where the final image is formed at the least distance of distinct vision,the magnifying power is:

$A$ distant hot air balloon subtends $0.25^o$ at the objective lens of an astronomical telescope. The image subtends $1.5^o$ at the eyepiece when viewed with a relaxed eye. The objective and eyepiece are in a $35 \ cm$ long tube. Find the focal length of the eyepiece lens in $cm$.

$A$ terrestrial telescope is made by introducing an erecting lens of focal length $f$ between the objective and eyepiece lenses of an astronomical telescope. This causes the length of the telescope tube to increase by an amount equal to

$A$ small telescope has an objective lens of focal length $144\;cm$ and an eyepiece of focal length $6.0\;cm$. What is the magnifying power of the telescope? What is the separation between the objective and the eyepiece?