In addition to using the Journey North line graph (which lets you see photoperiod lines for all ten mystery sites plus your location all at once), two teachers have shared how they also use a separate graph format too.
Instead of using lines to show photoperiod, this additional graph format uses "spaces" to show the hours in a day. Students darken the spaces before sunrise and after sunset, so that the resulting "light" spaces give an interesting picture of the day, the night and the changing photoperiod at that location. Here are two graph examples from teacher Susan Fineman's students, who made them on graph paper:
Susan uses this alternate graph from the beginning of the school year, and then uses it for the Mystery Classes too, as a way to show two formats of graphing the same data. Her helpful comments are below.
We calculate our local photoperiod each week from the beginning of the school year, and then graph the sunrise and sunset times on 24-cm wide grid paper, one row per week. The graph gives an interesting picture of the changing photoperiods and the place of the solstices and equinoxes.
The Pittsburgh Suntimes graph we keep all year is done on centimeter grid paper that has 24 boxes per row. We number the vertical lines from 0 to 2400. For a given week we write the date to the left of the row in the margin.
We round the sunrise time to the nearest quarter hour, plot that time with a vertical line, and shade in the boxes from 0 to the sunrise time. For sunset we plot the time rounded to the nearest quarter hour and shade the row from the sunset time to the 2400, the end of the row. The unshaded boxes represent the photoperiod and can be used to check photoperiod calculations.
As the weeks stack down the page from the beginning of school on, the
graph shows the days shortening from both ends till solstice time. The
weeks around the solstice show the unchanging sunset times (or sunrise
for the June solstice) and then the increasing photoperiods.