What would I be able to see with 70mm aperture telescope with 300mm focal length with maximum magnification of 150 x?

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    $\begingroup$ It really depends on 1) if it's an excellent or lousy telescope, 2) if it has an excellent or lousy mount, 3) if the seeing conditions and sky brightness in your area is excellent or lousy, 4) your degree of patience and willingness to learn how to use it. btw 70 mm, f=300 mm means it's f/4.3 which is pretty short. You would also need a 2 mm focal length eyepiece to get 150x, or a 4 mm eyepiece and 2x Barlow so something doesn't sound right about those numbers. If it's urgent you need to buy it, better not. $\endgroup$ – uhoh Jul 12 at 14:50

It's 70mm aperture, so the maximum useful magnification will be 165x.

If you have a 4mm eyepiece, you will have 75x magnification, and at that, you can expect to see rings of Saturn, moons of Jupiter in good conditions. Venus will show phases. I can't say much about Mercury.

You can see many surface features of the Moon. The view will be particularly good at 150x. You will have to use a 2x Barlow for that. Remember, the view will be good in good "seeing".

If you are in dark sky away from light pollution, you can expect to see many globular clusters and nebulas particularly, the Orion Nebula.

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