alrighty, try this. Ill attempt to convert you to the celestial light of idealism rather than the dark brown earthy slump of nieve realism. Down to earth indeed. 
when you look at the universe through more refined instruments than your eyes, you see it as completely different as you are recording properties completely incompatible with the senses you were born with.
This cannot be because the universe has changed significantly in the time it takes to turn the machine on, but because one set of properties is dependant on the other. But which ones?
Is a table actually red, or is it actually just emitting photons of a particular wavelength? If you are a realist, which set of properties is more real?
If you accept the problem above, you must ask, how do you know you have access to the properties that actually make up the universe? Maybe its not photon wavelength or redness that matters, but something entirely different which causes both those phenomena, and maybe that thing which is entirely different is unknowable.
Realism is the assumption that our experience is related to something independant of that experience in a “like” way. This thing which is independant cannot be talked about (if it could, then it wouldnt be independant now would it?). Also, if redness and photon wavelength are related, but not in a “like” way (they are completely different in form) then why would this independant universe and our perception be related in a “like” way? Why assume the universe is as you perceive it to be when scientific evidence already shows it isnt quite so simple?
There are many more problems closely linked with physics, but they’ll take more time to explain (look up the Heisenburg uncertainty principle for instance).
The idealist says, this situation is silly. There is experience, and we shouldnt even bother to consider what lies beyond it because the whole idea is rubbish. The universe and our experience are one and the same thing.
Would redness exist if there was nothing to see it? Id say no, as redness is a phenomena ONLY encountered in direct experience.
What about photon wavelength if the photon never interact with a another particle? Id say no, as photon wavelength is a phenomena ONLY encountered in indirect experience of particle interaction.
When you stop looking at a crystal, you still experience it (as does everything within a radius expanding at the speed of light) but indirectly though its effect on other things.
The more effect it has on your experience, the sharper it is determined and the more you can know about it, but there is no sense in which you can ever “experience” an object completely. This being the case, why asume that the object has ‘knowledge’ independant of your knowing it?
Gah, getting tired.
Ask for clarification for the more incoherant parts if you like, or Im sure someone else will deconstruct. Ill try and answer tomorrow.
In summary:
Idealism: All that is encountered in experience exists. Nothing else exists.
Realism: Lots of stuff exists (no idea what though), but some of it is unknowable, some of it can only be inferred, some of it can be directly experienced, some of it is necessarily the case, some of it is a combination of the above.
Cheers!
