This page shows Neptune moving against a background of stars, and it also shows its satellite Triton orbiting Neptune.
Neptune daily motion illustrated
Figure 1. Average of three 5-second exposures, enhanced using MaxIm DL's "Maximum Entropy, 8 stages," 2001 Aug 27.185 UT. Triton's predicted orbit is shown by a pattern of dots, and Triton itself is evident at the 4 o'clock position. Triton's location with respect to Neptune agrees with its predicted location to within 0.5 pixels. Neptune's brightness is magnitude 7.8, which makes it barely not visible to the naked eye (but easily visible with binoculars - if you know where to look). The faintest stars in this image are magnitude 15.0 (not bad for a total exposure of 15 seconds). The image size is 14.1 x 9.3 'arc (about 20% the area of the full moon). [This and all other images on this web page were taken with a Meade LX-200 10-inch Schmidt-Cassegrain f/6.3 telescope, Meade 416XTE CCD imager at prime focus; residential site at 200 feet ASL in Santa Barbara, CA.]
Figure 2. One day later, Neptune has moved westward (to the right). This is an average of six 3-second exposures, enhanced using MaxIm DL's "FFT High Pass C4035," 2001 Aug 28.233 UT. Triton's predicted orbit is shown dotted, and Triton is close to its predicted 2 o'clock location in its orbit.
Triton Orbital Motion
Figure 3. Sequence showing Triton's daily motion around Neptune in relation to its predicted orbit (using an image scale that is 4 times greater than the previous images). Triton's orbital period is 5.877 days, and its brightness is magnitude 13.5. Neptune's actual diameter is much smaller than the overexposed version of it in these images.
Figure 4. This is the actual size of Neptune's disk, which was obtained by adjusting the brightness and contrast of the previous figure's right panel image util it showed the correct area predicted for Neptune's disk. Neptune's disk diameter was 2.3 "arc on this date (2.1 pixels on the CCD imager).
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This site opened: August 28, 2001. Last Update: September 11, 2002