Look at the sky!

Well, I like to look at the sky.
I study law at university but sometimes I study astronomy too because is a good hobby for my mind.
Across the stars and the planets I discover the creation of God. Really the space is fantastic, and I would like to indicate for invite/implore you to reserve a time to appreciate this miracle of nature. Today you can observe the moon, Jupiter, the phases of Venus or the rings of Saturn.
Good night and look at the the stars!

Look at the Sky!

The first word and nouns are always capitalized in titles.

Well, I like to look at the sky.

You don't need to put "Well" in the beginning.  This is your first sentence so you're not transitioning from another sentence.  Remember, you're writing and not speaking.

I study law at university, but sometimes I study astronomy too because it is a good hobby for my mind.

Remember to use commas before contractions that connect other independent clauses.

Across the stars and the planets, I discover the creation of God. Really, space is fantastic, and I would like to indicate for you to reserve a time to appreciate this miracle of nature. Today, you can observe the moon, Jupiter, the phases of Venus or the rings of Saturn.

There's no need for an article in front of "space".  Why?  I honestly don't have a clear answer.  I think it maybe due to it being something with no real definite shape or something that cannot be accurately measured or represented.  I think you would call it an "unaccountable noun".  The word "time" is like this as well.  For example: "I traveled through time".  The word "time" does not need an article.  However, there are situations where words such as "space" and "time" do need an article.  For example: "He sat in the space next to her" or "She wanted to know the time".  In these cases, "time" and "space" each need an article because they are nouns that are specific and definitely can be accounted for.  I hope you understand.  If not, please do not be hesitant to ask, and I'll try to explain it another way.

I think by the word "indicate" you actually mean to use the word "encourage".  The word "indicate" is usually used to mean "show" or "imply something".  The word "encourage" means "to want someone to do something".  If it's not clear, try looking up the word on wordreference.com.

Commas have many uses, but one of their uses is to indicate to readers that they should make a slight pause when reading the sentence out loud. 

Good night and look at the the stars!