The objective of the Venus Section is to observe the planet on every clear night throughout each apparition. An apparition (of any planet) runs from its conjunction with the Sun to the next conjunction. Venus is an inferior planet, meaning that it has a smaller orbit than the Earth, and it therefore exhibits phases just like the Moon. Because Venus is comparatively near the Sun, it is very bright and produces an excessive amount of glare. The rather faint and elusive markings on the disk of Venus, normally of very low contrast, are therefore very difficult to see. Considerable controversy exists over the true nature of these dusky amorphous atmospheric features. It is not at all unusual for two observers, working on the same date with comparable instruments, to see striking dissimilar markings on the planet.

Even though Venus may reach a maximum angular distance from the Sun of 47°, the planet is usually observed near the times of sunrise or sunset. If Venus is seen against a dark sky, the effects arising from the excessive brilliance of the disk are pronounced.

At eastern (evening) apparitions, Venus is frequently low in the western sky where the effects of atmospheric refraction destroy good image quality. Seeing conditions are so poor at such times that most observers have adopted a practice of viewing Venus only when it has an altitude of at least 20° above the horizon. At times of western (morning) apparitions, it is possible to wait until the planet gains altitude and the background sky brightens considerably, and Venus can readily be followed into daylight. Observing Venus during daylight hours is an effective practice because most of the prevailing glare associated with the planet is reduced. However, observing Venus too far into the daylight hours can become a problem as solar heating produces turbulent air, which results in poor seeing. Another interesting fact is that many observers find the presence of a slight haze or high cloud often stabilizes and reduces glare conditions while improving definition. 

The programs are of particular interest to the beginner:

• Visual observations and drawings of atmospheric details in dark, twilight, and daylight skies.

• Observation of cusps, cusp-caps, and cusp-bands.

• Observation of dark hemisphere phenomena, including monitoring visibility of the ashen light.

• Observation of the shape of the terminator.

• Photography, CCD imaging, photoelectric photometry, and videos of Venus.

• Observation of the rare transits of Venus across the Sun.

• Simultaneous observations of Venus.

Widely spaced observations are of little value, and we must stress the importance of striving for systematic, regular studies carried out by many individuals using similar equipment and methods. Because of the elusive nature of markings on Venus, we are intensifying our effort to increase the number of simultaneous observations.

When observing with smaller apertures, one must seek a suitable combination of large angular diameter of Venus and large phase of the planet for successful detection of the elusive disk features. This combination of factors occurs about midway between the times of conjunction and greatest elongation. At these times, Venus has an angular diameter of approximately 16.0” (16 seconds-of-arc) and a gibbous phase. Use of magnifications in the range of 50D to 80D (where D is the diameter of the telescope in inches) is often practical when Venus is high in the sky.

It is important not to overlook various accessories that come with your telescope. Eyepieces should be of equal quality to the main optical system. When filters are used, they should be of known wavelength transmission should be used in conjunction with eyepieces actually employed for observations. Even though it may cost a little comfort and convenience, one should avoid using diagonals or any devices that orient the image of Venus contrary to the normal inverted view of a planet through an astronomical telescope. Low-transmission filters increase contrast and definition while limiting the effects of irradiation. It is just as vital to report negative results (no markings) as it is to record features that are present. Our fundamental goal is objectivity and realism.

It is important to use the appropriate drawing blanks and report forms prepared by the Venus Section. Forms are available for the cost of reproduction and postage from the Section coordinator.

Our ultimate goal is to assemble a completely homogeneous mass of accurate, reliable observational data collected over many apparitions, thereby permitting statistical analysis. We hope to derive sufficient information from painstaking observations and analysis to help provide some answers to the questions that continue to perplex us about our sister planet.