La astronomo rigardas tra la teleskopo.

In Esperanto, nouns normally end in -o. So astronomo means astronomer.

This makes word classes very easy to recognize:

• -o = noun
• -a = adjective
• -e = adverb
• -i = infinitive verb
• -as = present tense verb

So as soon as you see astronomo, you know it is a noun.

The ending -as marks the present tense in Esperanto. So rigardas means looks, is looking, or does look, depending on context.

Esperanto does not change the verb for different subjects:

• mi rigardas = I look
• vi rigardas = you look
• li rigardas = he looks
• la astronomo rigardas = the astronomer looks

So there is no special -s ending like English he looks.

Because Esperanto often uses the simple present tense -as for both English looks and is looking.

So rigardas can cover:

• looks
• is looking

If the context already makes the time clear, Esperanto usually does not need a separate progressive form like English does.

La means the.

So:

• la astronomo = the astronomer
• la teleskopo = the telescope

Esperanto uses la for definite nouns, much like English uses the. It does not change for gender, number, or case.

Also, Esperanto has no indefinite article like English a/an. So:

• astronomo = an astronomer / astronomer
• la astronomo = the astronomer

This is a very natural question, because both can make sense, but they emphasize slightly different things.

• tra la teleskopo = through the telescope
  This focuses on looking through the instrument itself, through its optical path.
• per la teleskopo = by means of the telescope / using the telescope
  This focuses more on the telescope as a tool.

In this sentence, tra matches the English phrasing through the telescope very directly.

Because teleskopo is the object of the preposition tra, and prepositions normally do not take the accusative -n just because they are objects of the preposition.

Here:

• tra la teleskopo = through the telescope

The noun stays as teleskopo, not teleskopon.

You would use -n for a direct object, for example:

• La astronomo rigardas la ĉielon. = The astronomer looks at the sky.

There, ĉielon gets -n because it is the direct object of rigardas.

Not necessarily. Rigardi can be used without stating exactly what is being looked at, just as English can say The astronomer is looking through the telescope.

The sentence tells us how the astronomer is looking, not explicitly what they are looking at.

If you wanted to include the thing being observed, you could say something like:

• La astronomo rigardas la stelojn tra la teleskopo.
  = The astronomer looks at the stars through the telescope.

Esperanto word order is fairly flexible, although subject + verb + other elements is the most neutral order.

So La astronomo rigardas tra la teleskopo is the most straightforward version.

Because Esperanto uses endings and prepositions clearly, you can sometimes move parts around for emphasis, for example:

• Tra la teleskopo rigardas la astronomo.

That is less neutral and more stylistic, but still understandable.

Esperanto pronunciation is very regular. The stress is usually on the second-to-last syllable of each word.

• la = lah
• astronomo = as-tro-NO-mo
• rigardas = ri-GAR-das
• tra = trah
• la = lah
• teleskopo = te-le-SKO-po

So the whole sentence is pronounced roughly:

lah as-tro-NO-mo ri-GAR-das trah lah te-le-SKO-po

Using la makes the telescope definite: the telescope.

Without la:

• tra teleskopo would sound more like through a telescope or through telescope(s) in general, depending on context.

With la:

• tra la teleskopo refers to a specific telescope, or one understood from the situation.

So the article helps show that the telescope is identifiable in context.

Yes. Both are possible translations.

Because rigardas is present tense, English may translate it in different ways depending on context:

• The astronomer looks through the telescope.
• The astronomer is looking through the telescope.

Esperanto itself does not force that distinction here. Context decides which English version sounds best.