Stellar parallax isn't a big effect. It wasn't even observable until the 1800s. Even the Hubble cannot measure parallax past about 10,000 lightyears, which is a

Stellar parallax isn't a big effect. It wasn't even observable until the 1800s. Even the Hubble cannot measure parallax past about 10,000 lightyears, which is about 10% of the size of the Milky Way. For earth bound telescopes at this scale, it's totally negligible.