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The approx. RA at midnight on the 21st of the month is:
Month, RA
1, 8
2, 10
3, 12 [equinox]
4, 14
5, 16
6, 18
7, 20
8, 22
9, 0 [equinox]
10, 2
11, 4
12, 6
The RA on the meridian at 6 pm on the 21st of the month is equal to the month number times two.
At 8 pm RA = 2M + 2 e.g. For Jan, RA = 2x1+2 = 4 at 8 pm
At midnt RA = 2M + 6 e.g. For Jan, RA = 2x1+6 = 8 at midnt
At 4 am RA = 2M + 10 e.g. For Jan, RA = 2x1+10 = 12 at 4 am
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