Roger,
I hope the information below is helpful. Note that because the moon is
so close there is an offset between the "true" geocentric coords. and
the apparent or topocentric coords., this effect is termed geocentric
parallax. See chap. 39 in Meeus for more details. The topocentric values
given below are for my latitude at +36.5deg.
Do the discussions of moon dialing you've read account for this slight
offset? In the the articles I've read, I've never seen mention of it but
I'm just starting to get interested after reading John Davis' glossary
(superbly done BTW) entry on Tidal Sundials and the 92.2 BSS Bulletin
article of the same. A sundial to indicate the tides (ocean tides),
surely you jest!(?)
Lunar Perigee:
12/22 10:44 UTC
12/22 02:44 PST
Earth-Moon distance: 356656.8 km (221616.8 miles)
True Equatorial RA: 05h 43m 17.7s Dec: +20°10'33"
Topocentric coordinates: RA: 05h 40m 50.3s Dec: +19°48'17"
Full Moon:
12/22 17:33 UTC
12/22 09:33 PST
Earth-Moon distance: 356733.3 km (221664.4 miles)
True Equatorial RA: 06h 01m 47.3s Dec: +20°33'07"
Topocentric coordinates: RA: 05h 59m 38.1s Dec: +19°45'39"
Best,
Luke
Roger Bailey wrote:
>
> When planning your solstice celebrations, the lunar perigee will be an
> additional focus this year. An interesting point is that your sundials will
> act as moondials on that night when the moon is full. The location of the
> moon is directly opposite the sun so the time is displaced by 12 hours. By
> the moon, a reading of 10:00 will be 10:00 pm. The solar shadow in the will
> be in the same position at 10:00 am.
>
> What about the declination? I know it will be large and positive but does
> anyone here know the lunar declination on 21/22 Dec when the moon is full?
>
> Roger Bailey
> N51 W115
