Answer: Find the star's luminosity or surface color and then find it on the H-R Chart
Explanation:
The parallax of a star is referred to as the angle that's shifted by a star when it's seen from the opposite sides of the Earth's orbit.
In a situation whereby an astronomer wants to find the distance to a main sequence star that isn't variable and is located too far away for parallax measurements, then she can find the star's luminosity or surface color and then find it on the H-R Chart.