Elegimos un ocular con menos aumento.

Elegimos can be either:

• present tense: we choose
• preterite (simple past): we chose

This happens because the nosotros form of elegir is the same in both tenses.

So this sentence can mean either:

• We choose an eyepiece with less magnification
• We chose an eyepiece with less magnification

Normally, the wider context tells you which one is meant.

Ocular means eyepiece.

It is a technical word used for the part you look through in an optical instrument, such as:

• a microscope
• a telescope
• binoculars

So un ocular = an eyepiece.

Because ocular is a masculine noun in Spanish: el ocular.

So with the indefinite article, it becomes:

• un ocular = an eyepiece

Even though the word ends in -ar, grammatical gender in Spanish is something you usually learn with the noun itself.

Here con means with, but in a descriptive sense: an eyepiece with less magnification.

So the structure is:

• un ocular = an eyepiece
• con menos aumento = with less magnification

This is a very normal way in Spanish to describe an object by one of its features.

In this sentence, aumento is being used as an uncountable idea, meaning magnification in general.

So:

• menos aumento = less magnification

Spanish often uses the singular in this kind of technical description.

You may also see aumentos in other contexts, especially when talking about magnification levels or powers, for example:

• a 40 aumentos = at 40x magnification

But here, menos aumento sounds natural because the speaker is talking about a lower degree of magnification, not a number of separate units.

Yes. Un ocular de menor aumento is also correct and very natural.

Both mean roughly the same thing:

• un ocular con menos aumento
• un ocular de menor aumento

A small nuance:

• con menos aumento sounds a bit more direct and conversational
• de menor aumento sounds slightly more technical or formal

Both are good Spanish.

Because menos is the usual word for less before a noun:

• menos aumento = less magnification

Menor is a comparative adjective meaning smaller / lower / lesser, and it usually appears in structures like:

• de menor aumento = of lower magnification

So both are possible, but the grammar changes:

• menos + noun → menos aumento
• menor + noun often appears with de → de menor aumento

Because menos aumento works as a general quantity expression, not a specific noun phrase.

Compare:

• con menos aumento = with less magnification
• con el aumento menor would sound different and less natural here

Spanish often leaves out the article in expressions of amount or degree like this.

This is the most natural, neutral word order:

• Elegimos = we choose / chose
• un ocular = an eyepiece
• con menos aumento = with less magnification

You could change the order in some contexts, but this version is the clearest and most standard.

For example, Con menos aumento elegimos un ocular is grammatically possible, but it sounds more marked and would usually need a special context or emphasis.

No. Spanish has other verbs that could fit, depending on nuance.

For example:

• Elegimos = we chose / choose
• Escogimos = we picked / selected
• Seleccionamos = we selected

In many contexts, these are similar. Elegir is a very common and natural choice.

Yes. This sentence is perfectly normal in Spain.

The vocabulary is standard and technical:

• elegimos
• ocular
• aumento

Speakers in many Spanish-speaking countries would also understand and use this sentence, especially in scientific or optical contexts.