Can you see deep sky objects with a 90mm refractor?

Not easily.

You might see the Andromeda Galaxy and a few planetary nebulae and bright objects like M42, M8, M20, M27...and a few globular clusters, but this size telescope doesn't have the light gathering ability to see most of the fainter objects and extragalactic objects. You need a 6-inch aperture (mirror or lens) telescope to start with, and an 8-inch is really the minimum to seriously see a large assortment of objects.


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