Sharp SL-550 Guia de Resolução de Problemas descarregar pdf (Página 26)

Set-up/Operation • A-26 •

Projecting the Sun and Moon

Note

These instructions apply to both the Standard and FiberArc Projectors.

The Sun

The Stareld Cylinder is unique because, unlike most of the cylinders, it has twelve

magnetic light blocks around its circumference. These light blocks mark the position of

the Sun along the ecliptic and when one is removed, it shows where the Sun would

appear in the sky for each month of the year. Each light block is located directly

above the name of a particular month listed on the cylinder platform on the projector.

The position of the Sun has been set for approximately mid-month with the exception

of March, June, September and December. On these months it has been offset to

show the Sun on the 22

of the month. This allows you to show the position of the

Sun in the daytime sky for the equinox and solstice dates. To remove a light block,

simply pull it out and place it on the magnetic strip located along the top front of

the projector. This will keep the light block from getting lost. Set the projector for the

desired latitude and turn the cylinder so that the “Sun” is seen on the eastern horizon.

This is sunrise. By turning on the daily motion switch, you will see the Sun slowly

move across the sky until it nally sets. This allows you to observe the elevation of the

Sun, location of sunrise and sunset and the relative amount of time it takes to cross

the sky for each month of the year making it easy to demonstrate the reason for the

seasons.

The Moon

While most people realize that the moon goes through a phase cycle, many don’t

understand that there is a clear-cut relationship between the phase of the moon and

what time of day it’s visible in the night sky. The reason we see the moon is because

it’s reecting sunlight back to us on Earth. While half the moon is always being lit by

the Sun, we don’t always see the lit side. The chart at the top of the following page

shows the relationship between the moon phases and the time of the day that they

can be seen.

Because the moon is normally found to travel close to the ecliptic, and since it has the

same apparent diameter as the Sun in the sky, the same light ports used to project the

Sun can be used to project the moon in the sky. In order to show the phases of the

moon, two identical sets of 5 magnetic moon phase inserts have been included in the

STARLAB accessory box.

One set of inserts can be used to show the waxing phases while the second set can

be used to show the waning phases. Each set includes a slim crescent, a wide cres-

cent, a quarter, a narrow gibbous and a wide gibbous. A full moon is projected by

removing the light block and leaving the light port completely open. For a new moon,

leave the light port blocked. Use the following procedure for setting a specic moon

phase.

Background

There are 29.5 days in one lunation, or complete set of moon phases. If the moon is

full on the 15th of a particular month, then it will be full about the 14th or 15th of the

following month. Because our months have lengths from 28 days (February) to 31

days, the phase repetition does not occur on the same day each month. In calendars

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 35 36

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Sharp SL-550 Guia de Resolução de Problemas Página 26

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