Problem about "Look At"
Alright,so when im saying "look at the...." do i use "a" as a preposition What I'm asking is how do I say look at the moon? Is it Mira a la luna. Or, Mira la luna.
6 Answers
Look at Mary - Mira a María
Look at the moon - Mira la luna
I am not completely sure about this but I think the "a" is only needed when referring to people and not to things.
Update:
When I think a bit more about it in English we would / could not say:
Look at the Mary or Look at moon.
We do not use the article "the" with Proper nouns. (ones with a capital letter)
There are a few exceptions for example: "Look at the United States of America"
But we should for other nouns - but some regions do not.
Example "I'm going t' pub" ( t' ) = to the.
English is easy right ? ha ha
¡Mira! translates as Look at it!
You will hear Spanish children shouting at their mothers - Mama ¡Mirame, mirame! Look at me. All children shout this quite a lot , in my experience...
Here's a couple of excerpts from the link I mentioned above:
Remember that mirar can mean 'to look at' - the 'at' is included so don't be tempted to always put 'a' after mirar.
Miró el reloj con disimulo. She glanced furtively at her watch.
Sometimes 'mirar' will however be followed by 'a' - why is that?
This 'a' is sometimes the personal 'a' that must go before a person (or a pet) when they are the noun receiving the object of the verb instead of doing the action of the verb.
When someone receives the action of the verb instead of doing it, they are called 'the direct object' . So when the direct object of a sentence is a person (or a pet) they must be preceded by the personal 'a'.
Eg: Estoy mirando las estrellas. I'm watching the stars.
The stars aren't doing the action of the verb (watching) instead they are receiving the action of the verb (being watched) but they are not a person or a pet so no personal 'a' is needed.
Estoy mirando a los niños. I'm watching the children.
The children aren't doing the action of the verb (watching) but they are receiving the action of the verb (they are being watched) and they are people so in this case the personal 'a' is needed.
At other times the 'a' is just part of a set expression and often means 'towards' or 'in the direction of':
Mirar algo = to look at something
Mirar a algo = to look in the direction of something
Mirar a alguien a los ojos. To look someone in the eyes.
Mirar a ambos lados antes de cruzar. To look both ways before crossing.
Mirar a la cámara. To look at the camera.
Mirar a otro sitio. To look away.
Mirar al futuro. To look towards the future.
Mirar al vacío. To look into space.
Perhaps this lesson will help - ver vs mirar - there is a section at the end about why you sometimes see mirar followed by an 'a'.

My grandmother would say "mira la luna"....I have come to realize Spanish speaking people are very "relaxed" in their speech, not too formal/proper. At least in my experience.
Mira la luna... Si dices: Mira a la luna, está en su fase menguante.