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MSC View Program / Exhibit

Figure 3a · Scanning telescope, Apollo 11 lunar orbit rev 30, 124:40:00 GET

The command module scanning telescope's view shortly after the LM lifted off from the Moon, recomputed from the 1969 inputs and compared with the 1972 printed figure.

View
Style
Star catalog
-50-50-40-40-20-2000202040405050X, degY, deg-0-5-10-15-20-30-35-40-45-50AlpheratzDiphdaNaviMenkarMirfakAldebaranRigelCapellaSiriusEarthVenusSaturnLunar lift-off REFSMMATGimbal anglesI = 49.1°M = 0.0°O = 0.0°

Seen from the spacecraft’s reconstructed position: bodies include parallax, and stars behind the Earth or Moon are hidden.

CSM position: Mission Report Table 7-II "Docking" (128:03:00.0), propagated back 03:23:00.

Residuals: recreation vs. the TN D-6853 (1972) scan (at the figure's own inputs)

BodyScan x, y (°)Recreation x, y (°)Δ (°)Within 2°
Sirius-45.59, 49.79-46.40, 49.730.81Yes
Rigel-32.11, 30.88-32.33, 30.610.34Yes
Capella25.47, 36.7625.21, 36.990.36Yes
Aldebaran-5.09, 27.00-5.12, 27.070.08Yes
Venus-1.89, 32.10-2.00, 33.691.60Yes
Mirfak31.57, 17.4731.23, 17.570.35Yes
Menkar-12.25, 1.60-12.03, 1.680.23Yes
Saturn-1.89, -4.20-1.88, -4.060.14Yes
Navi49.79, 0.7849.37, 0.880.43Yes
Earth2.40, -22.712.89, -22.570.51Yes
Alpheratz26.99, -26.6427.16, -26.430.27Yes
Diphda-22.77, -38.28-22.11, -38.070.70Yes

RMS 0.62°, max 1.60°. The plotting convention was chosen by fitting this figure, so this is a calibration, not an independent test (RMS ≤ 1° and max ≤ 2°: met).

How this was made

  1. Time. 124:40:00 ground elapsed time after the 13:32:00 UTC range zero on 16 July 1969 is 18:12 UTC on 21 July.
  2. Stars. The 148 stars of the note’s own RTCC catalogue (Besselian 1970) were transcribed by OCR; 22 rows the OCR could not read were read from the page images. Every row’s printed position was checked against the Yale Bright Star Catalog to within 0.05°. The 37 navigation stars use the unit vectors stored in the Apollo 11 command module computer.
  3. Earth and planets. Positions for that minute come from astronomy-engine, seen from the Moon’s center and rotated into the same B1970 frame.
  4. Spacecraft attitude. The stars are rotated through the Lunar lift-off REFSMMAT, then the gimbal angles I = 49.1°, M = 0°, O = 0°, in the order the guidance computer’s CALCGA routine uses, and then the 32.5° optics mounting (NB1NB2).
  5. Projection. The telescope looks along its shaft axis (trunnion 0°). The view is plotted as an azimuthal-equidistant (“fisheye”) projection ±50° across, with up toward increasing trunnion.
  6. Comparison. The 1972 figure was scanned at 300 dpi, registered to its ±50° frame, and each labeled body’s position was measured.

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