What is generally the best time for long-distance 10-meter band propagation via the F region?
Why The F region is ionized by solar ultraviolet and X-ray energy, so its ionization, and therefore the maximum usable frequency, peaks during daylight and falls off after sunset. Ten meters at 28 MHz sits near the top of the HF range, so it needs a high MUF, which only happens when sunspot numbers are high and the sun is up. Combine the two and the band opens worldwide from dawn until shortly after sunset around the peak of the solar cycle, then usually closes at night.
Watch out The nighttime choices describe how the lower bands like 40 and 80 meters behave, since D-layer absorption disappears after dark and their lower MUF still supports skip; at night 10 meters normally goes dead.
High band, high sun: 10 meters wants daylight plus lots of sunspots.