Astronomy Principles and Practice Fourth Edition.pdf

420 Practical projects
Figure 24.13. The variation of the solar corrected altitude with time over the period of meridian transit.
Example. From the curve obtained for March 29th 2000 (see figure 24.13),
Transit time: 12 h 22 m 10 s
Greenwich transit: 12 04 39·3
Longitude of Observatory (λ) : 17 30·7 West
Longitude of Observatory = 4 ◦ 23 ′ W
The maximum corrected altitude was determined to be 37 ◦ 43·′41.
Sun’s declination
According to the AA for March 29th 2000, δ ⊙ at 00 h (TDT) is
+3 ◦ 24 ′ 40·′′ 1 =+3 ◦ 24·′67.
The daily increase in δ ⊙ =+23·′33. By making a linear interpolation,
δ ⊙ at time of transit =+3 ◦ 37·′11
φ = 90 ◦ − 37 ◦ 43·′41 + 3 ◦ 37·′11 = 55 ◦ 53·′7.
µ Latitude of Observatory = 55 ◦ 53·′7
This information can now be used to draw the first position line.
Determination of a position line—observations B:
R 1 = 360 ◦ 31 ′ 36 ′′
R 2 = 359 ◦ 26 ′ 50 ′′
µ R = +0 ′ 47 ′′
For readings close to 60 ◦ , the scale error (r) =−20 ′′
µ Total correction to the readings =+0 ′ 27 ′′