File:AS08-12-2161 - Apollo 8 - Apollo 8 Mission image, Moon - NARA - 16668896.jpg

• Scope and content: Ganskiy crater at bottom.

The original database describes this as:

Description: Apollo 8,Moon. Image taken on Revolution 4. Camera Tilt Mode: Vertical Stereo. Sun Angle: 65. Original Film Magazine was labeled D. Camera Data: 70mm Hasselblad. Lens: 80mm; F-Stop: F/8; Shutter Speed: 1/250 second. Film Type: Kodak SO-3400 Black and White,ASA 40. Flight Date: December 21-27,1968.

Subject Terms: Apollo 8 Flight, Lunar Photography

Categories: Lunar Observations

Original: Film - 70MM B&W

Interior_Exterior: Exterior

Ground_Orbit: On-orbit

This photo was used in Figure 2-61 of the Analysis of Apollo 8 Photography and Visual Observations (SP-201), which has the following caption:

Control point 3, showing points 1, 2, and 3.

Text from Analysis of Apollo 8 Photography and Visual Observations referring to this figure is as follows:

For Apollo 8, a target for optical sightings on the lunar far side was called a control point (CP). Three control points were selected before the flight to make sightings easier. The control point identified as CP-1 was located 20° from the evening terminator and CP-2 was located 60° from the evening terminator. The control point identified as CP- 3 was located 60° from the morning terminator. The command module pilot (CMP) exercised an option of selecting sighting targets in real time and selected new targets for CP-1 and CP-2. These control points can be positively identified on Apollo 8 photography (figs. 2-59 and 2-60), and the same points were probably sighted on all three revolutions.

Sightings on CP-3 were made on revolutions 6 and 7. On revolution 6, the position of CP-3, which was selected preflight (point 1 in fig. 2-61), was entered into the onboard computer. The optics were then automatically driven to view this location. Because of the high Sun angle at this location and because the Sun line was so close to the line of sight, primarily only albedo differences could be seen, which made it difficult to identify the preselected CP. A bright spot (a crater with very high albedo) was sighted on revolution 6. During revolution 6, sextant photography was taken while sighting. Based on this photography, point 2 in figure 2-61 was probably sighted on during revolution 6. The poor visibility made it difficult to reacquire the same feature on revolution 7 as was sighted on revolution 6. Since sextant photography cannot be taken when the sextant is used for sighting, there is no sextant photography for revolution 7 to help in identification. Based on the different positions obtained on revolution 6 as compared to revolution 7 and based on similarity of albedo patterns, point 3 in figure 2-61 was possibly sighted on during revolution 7. Identification of point 3 is less certain than point 2. Because identification of CP-3 was difficult in real time and even more difficult on photography post-flight, the identification of CP-3 is uncertain. Therefore, a lower level of confidence exists in the position of CP-3 than in that of CP-1 and CP-2.

CP-3, point 2 was calculated at the time to be at Lat. -8.9229, Long. +97.1466, with a radius of 1739.524 km.