Planetary Observers / Solar System Observers Club - Sun and Moon

Planetary Observers / Solar System Observers Club Chair:

Aaron Clevenson
19411 Cluster Oaks Drive
Humble, TX 77346

E-mail: aaron@clevenson.org

The Projects for the Sun and Moon

SUN: Sunrise, Sunset Azimuth Positions

The Sun does not follow the same path across the sky every day. In the summer at northern latitudes, the Sun is high at midday, and in the winter, it is low in the southern sky. By observing the relative positions of the Sun at dawn or dusk, one can establish that the Sun does indeed shift along the horizon. Note where the Sun sets or rises once a week for at least four weeks in the spring or fall and for 6 to 8 weeks in the summer or winter. Be certain to observe from the same position each time. Note the time, day, month and year of each observation. At what season is the shift most noticeable?

SUN: Solar Eclipse

Solar eclipses are a rare and beautiful event, but can be hazardous. Never look at the sun without proper filtering, it can damage your eyesight permanently. During totality, when the sun is completely covered by the moon, and only the corona is visible, it is safe to look, but at other times a solar filter is a must. Observe a partial, total, or annular solar eclipse. Your notes should include the type of eclipse observed, the exact date and time of each phase of the eclipse: start of partial, start of total, end of total, end of partial. Include a sketch showing your observation at the point of maximum coverage, and include information about the location you were observing from: city and state, or latitude and longitude.

SUN: Sunspots

Sunspots are slightly cooler locations on the sun that are places where strong magnetic field lines emerge from the surface. They can be observed using the projection method or with proper solar filters for your telescope. Never look at the sun without proper filtering, it can damage your eyesight permanently. The projection method involves using either a very small telescope, or a piece of paper with a pinhole in it. In either case, sunlight passes through and is projected onto a white piece of paper. You then look at the image on the white paper. Observe the sun and make a full-disk sketch of the sun showing all visible sunspots. At least one sunspot is required. Note the umbrae and also the penumbrae that are visible. Record the date and time of your observation. If you are interested in further study of sunspots, check into the AL’s Sunspotters Club.

MOON: Maria

A naked eye or binocular view of the Moon shows two distinct types of lunar surface material, the maria and the highland areas. Both areas have their own visual characteristics. The highland material reflects light to a greater degree and appears very rough in character. The various mare areas are much darker and appear smoother. Before the telescope, these dark areas were speculated to be bodies of water, hence their name mare which is sea in Latin. Observe these "seas" or maria with your telescope. What evidence do you find that these are not bodies of water? If you are interested in further study of the moon, check into the AL’s Lunar Club and the Lunar II Club.

MOON: Highlands

Examine the bright, rough areas of the Moon. These are called the Lunar Highlands. If we are to assume that craters formed everywhere on the Moon at approximately the same rate, what can you conclude about the relative ages of the Lunar Highlands and the darker Maria? Why?

MOON: Crater Ages

Twelve degrees south of the Lunar equator and about halfway from the eastern limb (Selenographic east, not east in Earth's sky) to the center of the Moon is one of the most prominent craters on the Moon. Theophilus is 100 km (62 miles) in diameter and has a terraced wall and a group of central mountains. Just to the south and west of Theophilus is another crater of equal size, Cyrillus. Remembering that the Lunar surface is constantly being eroded away by countless meteoroid impacts, which crater would you say is the oldest and why? Sunrise on Theophilus is five days after New Moon. A six or seven day old Moon should show the area well.

MOON: Scarps

The Straight Wall, or "Rupes Recta" in Latin, is the best known scarp (fault area) on the Moon. When viewed less than a day after First Quarter, the fault's long thin dark shadow is hard to miss. Contrary to its appearance, it is a moderate slope and not steep. The Straight Wall is located at 22° South and 7° West. Just to the scarp's west is a small sharply defined crater called Birt. If Birt is known to be 17 km. (10.5 miles) in diameter, estimate the length of the Straight Wall.

MOON: Occultations

Lunar occultations occur when the Moon, in its eastward path about the Earth, passes in front of stars or planets and eclipses them. The precise timing of the occultation concerns that instant when the occulted object seems to blink out behind the Lunar limb or reappears from behind the Lunar limb. These timings supply vital information regarding the Earth-Moon orbit and any changes in the velocity or distance of that orbit. Less frequent, but neater to observe, are occultations by the moon of the naked eye planets. These events, both of stars and planets, are always highlighted ahead of time in the astronomy magazines. Occultations of stars in the Hyades cluster are fairly common. Periodically also, the Pleiades cluster is crossed by our natural satellite. If this type of observation is appealing to you there are resources available that tell you how to do really worthwhile and productive work. You will need to have a telescope available, however. See the resources in the back of the book. Note the name of the object occulted, the day, month, year, the universal time of the object's disappearance and reappearance, and the place of your observations.

Moon: Lunar Eclipse

Lunar eclipses happen twice a year and occur when at least some part of the moon moves into at least part of the Earth’s shadow. They occur only when the moon is in full phase. The types of lunar eclipse sand their meanings are:
• Penumbral Eclipse – The moon only slightly darkens. From anywhere on the moon you would see the Earth partially cover up the Sun.
• Partial Eclipse – Part of the moon becomes very dark, part of it remains bright. If you were on the moon in the darkened part, you would see the Sun completely covered by the Earth. From the bright part of the moon, the Earth would cover only part of the Sun.
• Total Eclipse – The entire moon becomes dark. From anywhere on the moon, the Earth would completely cover the Sun. Lunar eclipses can be rated as to how dark they really get. The ratings are the Danjon Scale. • L0 – Very dark: Moon is almost invisible, especially at mid-totality.
• L1 – Dark: Moon is dark gray or brownish, very hard to see details.
• L2 – Deep red of rust, dark center, edge is brighter.
• L3 – Brick red, rim is brighter and yellowish.
• L4 – Bright copper-red or orange, rim is bright and bluish.

Observe a lunar eclipse. Note the exact dates and times of: start of partial eclipse, start of total eclipse, end of total eclipse, and end of partial eclipse. Also include your estimate of the rating from the Danjon Scale if it is a total eclipse.

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