NASA / Astronomical League
Transit of Venus
Certificate Observing Program

Information about the Venus Transit Certificate:

• You must be a Astronomical League member to receive this certificate.
• When you have completed all criteria send it to:  lmayo@pop600.gsfc.nasa.gov
• For more information about the Venus Transit go to: http://sunearth.gsfc.nasa.gov
   

Observing the Sun:

Before you start any solar observing program, make absolutely certain that you have safe filters and a safe set-up.

Only use filters from reputable sources, and never use a "solar filter" that screws into an eyepiece. As Richard Hill states in Observe and Understand the Sun:
"Observing the sun is the only inherently dangerous observing an amateur astronomer can do. Be aware of this at all times and take all necessary precautions. If you do not know a filter or procedure is safe then do not use it! Always err on the side of safety. An eye once damaged is forever damaged. Filters that let too much INFRARED light through can burn an eye if used visually. There is NO PAIN when this happens. Burned retinas can not be repaired. Excessive ULTRAVIOLET light has been shown to cause cataracts. So be very careful."

OBSERVATIONAL COMPONENT

1. Derive the distance to Venus: The distance to Venus can be derived by measurement of the parallax angle as observed by two observers spaced widely in latitude. To do this, the astronomer shall take observations from widely spaced observatories from the SECEF Venus Transit web site (http://sunearth.gsfc.nasa.gov). Basically, the linear separation of two paths of the planet across the sun is measured and ratioed to the diameter of the sun to get an angular separation, Alpha. Then, knowing the distance between the two observers/observatories, one can calculate the distance to Venus using the small angle formula: L = [(d/2) / tan(a/2)] ~ d / (a/2), where alpha is expressed in radians and a/2 is the angle of parallax..

2. Derive Venus' orbital velocity at the time of transit: Once the distance to Venus is known, its orbital velocity can be estimated by first calculating an angular velocity and then using the small angle formula above. Using a telescope, estimate the angular movement of Venus across the sun over a given time period. The transit lasts about six hours in its entirety but East Coast observers will have less than two hours to view the transit after sunrise. If your own observations are not possible, refer to the sunearth.gsfc.nasa.gov web site and derive an angular motion from two different images spaced in time from the same observatory using the sun's angular diameter as a reference.

Angular Displacement = a = (x₂ - x₁) * W_sun = Dx * W_sun ; where W_sun = angular diameter of the sun ~ 0.5 degrees or 0.0087 radians and Dx is the length of a line between two observations of Venus spaced in time, expressed as a percentage of the diameter of the solar disk.

** (then Angular Velocity = w = a / (t₂ - t₁) = a / Dt)

 

To calculate orbital velocity, use the following formula:

Orbital Velocity = v = [(D * tan(a)] / Dt; where D = 1 A.U.

 

Just for fun: Calculate the mass of the sun via:

M_sun = (4p² * A_v³) / (G * P²)

Where Av is the mean distance from the sun to Venus, G is the gravitational constant, and P is Venus' orbital period. Make sure to use similar units of time and distance.

 

3. Detect the Venusian atmosphere: Using a telescope and solar filter, the astronomer will observe and sketch/photograph the "Halo effect" which occurs both at entrance and exit from the sun's disk. This optical phenomenon, first viewed in 1761, is caused by the scattering of light through the planet's dense atmosphere as was suggested by the Russian astronomer, Lomonosov in that year. One can also view the "Black Drop effect" apparent near 2nd and third contact where the disk of Venus appears to bleed into the solar limb. This effect is due to difficulties in resolving features of high contrast such as a dark Venus silhouette and a bright sun and made accurate timings of the transit next to impossible contributing significantly to error in the Earth-Venus distance calculation.

4. Time the transit (1^st, 2^nd, 3^rd, and 4^th contact): Using a telescope and a clock standardized to the official U.S. time as specified by NIST, observe each contact (US observers will be able to see only 3^rd and 4^th contact) and note the time of contact.

OUTREACH COMPONENT

To satisfy the requirements for the outreach component, Astronomical League members must satisfy item 1 and then any one of items two through four.

1. Register for Sun-Earth Day
2. Participate with school, museum, or community groups: Give a presentation in a school, museum, or civic group (e.g. Girl and Boy Scouts) on some aspect of the Transit of Venus.
3. Hold a SUN PARTY: Sponsor a solar observing event on the day of the transit. Get at least 25 people to actually view the sun with Venus in transit either directly through a telescope or via the Venus Transit web images or web cast (http://sunearth.gsfc.nasa.gov).
4. Work with a local school to create and bury a time capsule. The capsule can be dug up in either 2012 or 2117. GPS coordinates of the capsule must be provided.

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