You should be aware that the primary purpose of an astronomical telescope is light gathering, not magnification. All light that falls on the primary (mirror or lens) is focused into your eye and so the light gathering power is proportional the square of the radius of the primary.
The magnification depends on the focal length of the primary divided by the focal length of the secondary lens. Typically, because the radius of the primary is fixed, you need a secondary with a shorter focal length to increase the magnification. Of course, that makes it harder to focus.
The "resolving power" of a telescope is proportional to the radius of the primary. If two points on, say, the moon, are within the resolving power, you will not be able to tell them apart no matter how much you try to magnify. Stars are so far away they are well within the resolving power of any telescope. No matter how much you try to magnify a star it will look like a point of light. (Actually, since no telescope is perfect, a star will show as a small "blur", the better the telescope, the smaller the blur. Increasing the magnification will just enlarge the blur. Except to see star fields, like star clusters, there is no reason to use high magnification to look at stars.)
Looking at planets or the moon is a good reason to use high magnification (short focal length secondary lens) but, as I said, it becomes harder to focus and there is no point in magnifying beyond the resolving power of the telescope.
By the way, the fact that stars are points and planets are disks is the reason stars "twinkle" and planets don't. When I first was told that stars "twinkle" because of the atmosphere, that made no sense to me at all. After all, the entire atmosphere is between the Earth and both stars and planets- and planets don't "twinkle"!
But stars are "points of light". Any slight tremble in the atmosphere will affect the light and make it "twinkle". Planets are not. Even with the naked eye, though we don't see it clearly, planets are "disks". A change in a tiny part of the atmosphere won't affect any but a small portion of that disk so we do not see an appreciable change in the brightness.
