In the telescope you see two Suns: the one in the tray, and the one brought down by the sextant’s mirrors. Bring the mirror image down until it rests on top of the reflection, edges just touching. The reading is then twice the altitude of the Sun’s lower limb, so you work it as a lower-limb sight.

The order matters, as at sea:

Index correction, applied to the reading (on the arc, take it off; off the arc, add it on).
Halve it: that is Ha. There is no dip.
Main correction from the almanac, Sun lower limb, entered with Ha: Ho.

An October afternoon. Reading 64°18.4', index error 2.0′ on the arc.

64°18.4' − 2.0′ = 64°16.4'. Halved: Ha = 32°08.2'.

Main correction (Sun, lower limb, October to March) for 32°08.2': +14.7′. Ho = 32°22.9'.

From Ho on, the sight is worked exactly as at sea. Try some:

A day in November. Sun, the image in the mirrors resting on its reflection in the tray. Sextant reading 51°40.6'; index error 4.0′ off the arc.

Ha (index correction applied, then halved)

degrees and minutes, like 51 35.6

Ho (Sun, lower limb)

degrees and minutes, like 51 35.6

Altitude corrections

Dip

Height, ft	Dip
4	−1.9'
5	−2.2'
6	−2.4'
7	−2.6'
8	−2.7'
9	−2.9'
10	−3.1'
11	−3.2'
12	−3.4'
13	−3.5'
14	−3.6'
15	−3.8'
16	−3.9'
17	−4.0'
18	−4.1'
19	−4.2'
20	−4.3'
21	−4.4'
22	−4.5'
23	−4.7'
24	−4.8'
25	−4.8'
26	−4.9'
27	−5.0'
28	−5.1'
29	−5.2'
30	−5.3'

Height, m	Dip
1.0	−1.8'
1.1	−1.8'
1.2	−1.9'
1.3	−2.0'
1.4	−2.1'
1.5	−2.2'
1.6	−2.2'
1.7	−2.3'
1.8	−2.4'
1.9	−2.4'
2.0	−2.5'
2.1	−2.6'
2.2	−2.6'
2.3	−2.7'
2.4	−2.7'
2.5	−2.8'
2.6	−2.8'
2.7	−2.9'
2.8	−2.9'
2.9	−3.0'
3.0	−3.0'
3.1	−3.1'
3.2	−3.1'
3.3	−3.2'
3.4	−3.2'
3.5	−3.3'
3.6	−3.3'
3.7	−3.4'
3.8	−3.4'
3.9	−3.5'
4.0	−3.5'
4.1	−3.6'
4.2	−3.6'
4.3	−3.6'
4.4	−3.7'
4.5	−3.7'
4.6	−3.8'
4.7	−3.8'
4.8	−3.9'
4.9	−3.9'
5.0	−3.9'
5.1	−4.0'
5.2	−4.0'
5.3	−4.1'
5.4	−4.1'
5.5	−4.1'
5.6	−4.2'
5.7	−4.2'
5.8	−4.2'
5.9	−4.3'
6.0	−4.3'

Sun: main correction

Enter with Ha (apparent altitude). October to March.
Ha from	to	Lower limb	Upper limb
10°00.0'	10°07.9'	+11.0'	−21.3'
10°08.0'	10°20.3'	+11.1'	−21.2'
10°20.4'	10°33.1'	+11.2'	−21.1'
10°33.2'	10°46.3'	+11.3'	−21.0'
10°46.4'	11°00.2'	+11.4'	−20.9'
11°00.3'	11°14.5'	+11.5'	−20.8'
11°14.6'	11°29.5'	+11.6'	−20.7'
11°29.6'	11°45.0'	+11.7'	−20.6'
11°45.1'	12°01.2'	+11.8'	−20.5'
12°01.3'	12°18.2'	+11.9'	−20.4'
12°18.3'	12°35.9'	+12.0'	−20.3'
12°36.0'	12°54.3'	+12.1'	−20.2'
12°54.4'	13°13.7'	+12.2'	−20.1'
13°13.8'	13°33.9'	+12.3'	−20.0'
13°34.0'	13°55.1'	+12.4'	−19.9'
13°55.2'	14°17.4'	+12.5'	−19.8'
14°17.5'	14°40.8'	+12.6'	−19.7'
14°40.9'	15°05.5'	+12.7'	−19.6'
15°05.6'	15°31.5'	+12.8'	−19.5'
15°31.6'	15°58.9'	+12.9'	−19.4'
15°59.0'	16°27.8'	+13.0'	−19.3'
16°27.9'	16°58.4'	+13.1'	−19.2'
16°58.5'	17°30.9'	+13.2'	−19.1'
17°31.0'	18°05.4'	+13.3'	−19.0'
18°05.5'	18°42.0'	+13.4'	−18.9'
18°42.1'	19°21.0'	+13.5'	−18.8'
19°21.1'	20°02.7'	+13.6'	−18.7'
20°02.8'	20°47.3'	+13.7'	−18.6'
20°47.4'	21°35.0'	+13.8'	−18.5'
21°35.1'	22°26.3'	+13.9'	−18.4'
22°26.4'	23°21.6'	+14.0'	−18.3'
23°21.7'	24°21.2'	+14.1'	−18.2'
24°21.3'	25°25.8'	+14.2'	−18.1'
25°25.9'	26°35.9'	+14.3'	−18.0'
26°36.0'	27°52.2'	+14.4'	−17.9'
27°52.3'	29°15.5'	+14.5'	−17.8'
29°15.6'	30°46.8'	+14.6'	−17.7'
30°46.9'	32°27.2'	+14.7'	−17.6'
32°27.3'	34°18.0'	+14.8'	−17.5'
34°18.1'	36°20.7'	+14.9'	−17.4'
36°20.8'	38°37.1'	+15.0'	−17.3'
38°37.2'	41°09.3'	+15.1'	−17.2'
41°09.4'	43°59.8'	+15.2'	−17.1'
43°59.9'	47°11.2'	+15.3'	−17.0'
47°11.3'	50°46.8'	+15.4'	−16.9'
50°46.9'	54°49.9'	+15.5'	−16.8'
54°50.0'	59°23.6'	+15.6'	−16.7'
59°23.7'	64°30.4'	+15.7'	−16.6'
64°30.5'	70°11.4'	+15.8'	−16.5'
70°11.5'	76°24.3'	+15.9'	−16.4'
76°24.4'	83°02.7'	+16.0'	−16.3'
83°02.8'	89°55.5'	+16.1'	−16.2'
89°55.6'	90°00.0'	+16.2'	−16.1'

Stars and planets work the same way, with the stars column of the corrections; the Moon too, with its own tables. The Sun is the easy one to start with: it is bright in the tray, and easy to bring down.

Working a land sight

Dip

Sun: main correction