Observations of the Summer Solstice, 1813, with the Mural Circle, at the Royal Observatory

XXXIII. Observations of the Summer Solstice, 1813, with the Mural Circle, at the Royal Observatory. By John Pond, Esq. Astronomer Royal, F. R. S. Read July 8, 1813. | Date | Barometer | Therm. | In. | Out. | Refraction | Observations as given by the Instrument | Equations for N. P. D. | Equations for Zenith Distance | Semidiameter of the O by Nautical Almanack | Reduction to the Solstice | Solstitial Zenith Distance with Parallax | Solstitial N. P. D. with Parallax | Correction for O's Lat. | Solstitial Zenith Distance corrected for O's Lat. | Solstitial N. P. D. corrected for O's Lat. | |------|-----------|--------|-----|------|------------|----------------------------------------|------------------------|-------------------------------|---------------------------------|--------------------------|----------------------------------|----------------------------------|-----------------------------|---------------------------------|----------------------------------| | June | | | | | | | | | | | | | | | | | 10 | 29.57 | 62 | 69 | 0 | 30.3 | ○ LL 67° 14' 21.9" | ○ -0.6 | ○ -38° 31' 22.1" | ○ 15° 46.5 | ○ -26° 44.7 | ○ 28° 0° 58.9 | ○ 66° 32' 20.4 | ○ +1.0 | ○ 28° 0° 59.9 | ○ 66° 32' 21.4 | | 11 | 29.81 | 64 | 71 | 29.6 | 30.1 | ○ UL 66° 38' 18.9" | ○ -0.6 | ○ 22.1 | ○ 15° 46.5 | ○ 22° 16.2 | ○ 5° 7 | ○ 18° 2 | ○ +1.0 | ○ 5° 7 | ○ 19° 2 | | 12 | 29.70 | 64 | 74 | 30.1 | | ○ LL 67° 5' 48.1" | ○ -0.6 | ○ 22.1 | ○ 15° 46.4 | ○ 18° 12.1 | ○ 5° 7 | ○ 19° 1 | ○ +1.0 | ○ 5° 7 | ○ 20° 1 | | 13 | 30.02 | 61 | 66 | 30.9 | | ○ UL 66° 30' 36.9" | ○ -0.6 | ○ 22.1 | ○ 15° 46.3 | ○ 14° 32.4 | ○ 5° 7 | ○ 21.1 | ○ +0.9 | ○ 1° 5 | ○ 22° 0 | | 15 | 29.62 | 60 | 66 | 30.1 | | ○ LL 66° 56' 2.3" | ○ -0.6 | ○ 22.1 | ○ 15° 46.1 | ○ 8° 26.7 | ○ 5° 7 | ○ 19.0 | ○ +0.7 | ○ 5° 8 | ○ 19° 7 | | 21 | 30.15 | 57 | 60 | 30.0 | | ○ UL 66° 16' 9.3" | ○ -0.6 | ○ 22.1 | ○ 15° 45.8 | ○ 0° 19 | ○ 1° 1 | ○ 22.6 | ○ +0.1 | ○ 1° 1 | ○ 22° 5 | | 23 | 30.17 | 56 | 59 | 30.8 | | ○ LL 66° 48' 7.4" | ○ -0.6 | ○ 22.1 | ○ 15° 45.6 | ○ 0° 32.0 | ○ 5° 8 | ○ 20.0 | ○ -0.3 | ○ 5° 8 | ○ 19° 7 | | 25 | 30.18 | 59 | 64 | 29.9 | | ○ UL 66° 18' 47.8" | ○ -0.6 | ○ 22.1 | ○ 15° 45.6 | ○ 2° 41.1 | ○ 1° 1 | ○ 21.6 | ○ -0.3 | ○ 5° 9 | ○ 21° 3 | | 27 | 30.07 | 64 | 70 | 30.2 | | ○ LL 66° 54' 6.5" | ○ -0.6 | ○ 22.1 | ○ 15° 45.6 | ○ 6° 29.3 | ○ 5° 7 | ○ 21.2 | ○ -0.2 | ○ 5° 9 | ○ 21° 0 | | 28 | 29.94 | 61 | 67 | 29.7 | | ○ UL 66° 25' 9.0" | ○ -0.6 | ○ 22.1 | ○ 15° 45.6 | ○ 9° 0.4 | ○ 1° 1.8 | ○ 23.3 | ○ -0.1 | ○ 1° 1 | ○ 23° 2 | | 29 | 29.75 | 64 | 74 | 30.0 | | ○ LL 66° 59' 32.2" | ○ -0.6 | ○ 22.1 | ○ 15° 45.5 | ○ 11° 56.1 | ○ 5° 8 | ○ 20.0 | ○ -0.3 | ○ 5° 8 | ○ 20° 0 | | July | 1 | 29.67 | 62 | 65 | 29.6 | ○ UL 66° 35' 7.1" | ○ -0.6 | ○ 22.1 | ○ 15° 45.5 | ○ 19° 0.7 | ○ 5° 9 | ○ 20.9 | ○ +0.3 | ○ 5° 9 | ○ 21° 2 | | 2 | 29.75 | 60 | 62 | 31.8 | | ○ LL 67° 10' 44.8" | ○ -0.6 | ○ 22.1 | ○ 15° 45.5 | ○ 23° 9.5 | ○ 5° 9 | ○ 21.0 | ○ +0.4 | ○ 5° 9 | ○ 21° 5 | Mean of 13 Observations Parallax = 4",0 Nutation = 6",5 Mean Obliquity Mean Obliquity at Summer Solstice, 1812 Mean of Two Observations or Mean Obliquity, Jan. 1, 1813 * I avail myself of this opportunity of correcting a very small error that was made in computing the summer solstice of 1812. The correction for the sun's latitude should have been 0",6 instead of 0",9, and should have been applied with the contrary sign. The obliquity thus corrected will be 23° 27' 50",5.