# Do radio telescopes see other stars better at night?

As you know, we don’t see stars with the naked eye during the day because of the visible glare of our Sun.

As I understand our Sun emits radio frequency waves, too. Is there a radio ‘glare’ from the Sun such that radio telescopes can better focus on other stars during the night?

The Sun doesn't substantially impact radio observations during the day, because radio telescopes operate at long wavelengths. In general, light at longer wavelengths scatters less than light at shorter wavelengths, and so visible light from the Sun scatters much more than radio waves from the Sun.$$^{\dagger}$$ The former effectively fills the daytime sky, while the latter does not, leaving the radio sky dark even during the day. Couple this with the fact that the Sun - though bright in radio waves - is not extremely bright compared to other radio sources,$$^{\ddagger}$$ and you find that daytime radio observing isn't significantly different than nighttime observing.
$$^{\dagger}$$The same is true for light traveling through interstellar space, which is why infrared and radio emission can travel through dust while visible and ultraviolet light can't; you need wavelengths much larger than the sizes of dust grains for minimal extinction.
$$^{\ddagger}$$A commonly quoted value is that around $$\sim1\text{ GHz}$$, the Sun has a flux density of $$S_{\nu}\sim10^6\text{ Jy}$$ when it's quiet, with an increase of 1-2 orders of magnitude during active periods. That's only a couple of orders of magnitude brighter than the next brightest sources in the sky, and the difference shrinks substantially in the $$\sim100\text{ MHz}$$ regime.