Minor illusion says:
If you create an image of an object--such as a chair, muddy footprints, or a small chest--it must be no larger than a 5-foot cube. The image can't create sound, light, smell, or any other sensory effect. Physical interaction with the image reveals it to be an illusion, because things can pass through it.
I'd rule that magnification is an "other sensory effect", so this doesn't work. See this great answer for further details.
You create a nonmagical trinket or an illusory image that can fit in your hand and that lasts until the end of your next turn.
A spyglass is not a trinket. It's worth 1000gp. Examples of trinkets can be found on this table in the basic rules. None of these come even close to the value of a spyglass (their values aren't even listed - they aren't worth much at all).
This ruling is further supported by the Sage Advice Compendium when it says:
What kinds of things count as “nonmagical trinkets” for prestidigitation?
Prestidigitation can create a little bauble, the nature of which is up to the spellcaster and the DM. See the Trinkets table in the Player’s Handbook for examples.
That's the closest thing to a RAW answer we have here, and I think it's pretty clear, especially with the explanation from Sage Advice. Further, there's a pretty clear (to me at least) sense in which these spells are not meant to create things of significant value, and magnifying glass and a spyglass are valued at 100 gp and 1000 gp, respectively. Why does this value matter? A cantrip than can be cast at will with no cost serves as a functional permanent replacement for these items if they are allowed to create them.