Why is it better for astronomers to measure parallax by observing every six months instead of observing every year

  The baseline is longer

Explanation:

Each year, the Earth is in the same place relative to the sun, give or take a quarter million miles. Hence the sky pretty much appears the same.

In 6 months, the Earth is about 2 AU (about 186 million miles) from where it was, so the baseline for observing parallax is much longer.

The longer the baseline, the better, when measuring parallax.

separation of church and state? not sure what you mean.

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