Re: Solstice Perigee
Hello Troy, You're welcome! Regarding the reporting of the upcoming full moon (and associated clamor), a very good local paper, The San Jose Mercury, today reported, see URL and snippet below, that the 1912 full moon was actually a far brighter moon. I don't know, perhaps 0.2% is far brighter but I wouldn't have thought so. I'm not sure whether its this lunar lemming spin or the Old Farmer's Almanac hoax which is actually more annoying. Perhaps it was the added So there! that did it... http://www.mercurycenter.com/premium/front/docs/moon21.htm As for Crazy Horse and the 1866 date, the editors of Sky Telescope magazine did some research and found that 1912 was actually a far brighter moon than in 1866 or 1999. The magazine looked at actual moon perigee distances from the years 1800 to 2100 and found that the moon was brighter (closer) in 1912 and only slightly less bright in 1893 and 1930. So there! Best, Luke [EMAIL PROTECTED] wrote: Thanks for the very detailed explaination Luke. So is the answer 27.2% brightness difference between the June Moon and the Dec. Moon? That would mean the paper was wrong. The newspaper also predicted the January Moon would be even brighter (something you didn't cover). Another thing that bothered me is after the astronomical explanation, they author of the article interviewed an astrologer, who basically told him the moon was in Cancer (it may have been another constellation for you sticklers), and the brightness didn't matter. Then he rambled off general predictions depending on your astrological sign. It's hard to believe we are about to enter the 2000s...Frankly, I'm disappointed. No flying cars, and astrologers are still taken seriously. ~Troy
Re: Solstice Perigee
I decided to get out xephem 3.0 and do some calculations for the upcoming solstice/lunar perigee/full moon. Times are Mountain Standard Time (UT - 7). According to the xephem's solver, here are the time and other values at the solstice (I found this by using the solver to minimize the solar declination): Limb Equ: Geo 2000.0 12/22/1999 0:26:37 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 17:59:59.17 -23:26:21.5 0.9837 7:48 17:04 Moon 5:34:25.99 19:57:13.2 356675 173.1 100 17:28 7:33 Lunar perigee (found by minimizing lunar-earth distance): Limb Equ: Geo 2000.0 12/22/1999 3:54:08 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 18:00:37.55 -23:26:21.2 0.9837 7:48 17:04 Moon 5:43:46.84 20:11:20.4 356654 174.9 100 17:28 7:33 Full moon (full moon calculation built in): Limb Equ: Geo 2000.0 12/22/1999 10:33:19 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 18:01:51.38 -23:26:19.0 0.9836 7:48 17:04 Moon 6:01:49.93 20:33:15.8 356731 -177.1 100 17:28 7:33 Finally, here is the upcoming perihelion, almost twelve days later (found by minimizing the solar-earth distance): Limb Equ: Geo 2000.0 1/02/2000 23:35:12 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 18:52:59.00 -22:52:49.6 0.9833 7:51 17:12 Moon 16:13:27.56 -16:35:37.9 405794 -37.9 11 4:07 14:40 I am not claiming high precision; I used default settings for comparison tolerances, etc. Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- Where there is a will, there is an Inheritance Tax.
Re: Solstice Perigee
[EMAIL PROTECTED] wrote: In regard to the excitement over the close perigee occuring when the earth is closest to the sun (very close to the December solstice.) My local paper made a comment that the Moon will appear 17% larger than a full moon last summer (that is in June-July for you down underlings), but the full moon in January will appear 40% larger. I suspect it was a misprint, but I thought I'd send it out so you could chew on it. ~troy Hello Troy, Well, let's find out. Full Moon June '99: 06/28 21:38 UTC Earth-Moon distance: 401955.3 km (249764.0 miles) True Equatorial RA: 18h 26m 34.5s Dec: -20°10'09 Topocentric coordinates: RA: 18h 26m 58.8s Dec: -20°25'17 Full Moon Dec.'99: 12/22 17:33 UTC 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 The calculated ratio between the full moon distances above is 1.1267. However, to keep things straight note that the June '99 full moon is about three days after apogee and the Dec '99 full moon is very close to perigee, i.e., approx. 6hrs after. We'll see that this really doesn't matter much though and will keep things relative to the June '99 full moon. The intensity of light varies as the inverse square of the distance between a light source and the observer. Therefore, the intensity difference between these two distances is 1.2696 or approximately 27%. This is not trivial by any means. The trivial part is as follows. There has been some recent clamor about the claim of the Dec. 22 full moon not being the brightest full moon in 133yrs. Well, the fact is that those denying this are correct but what is the real magnitude of such a disclaimer? Well, let's take the same June '99 full moon distance, i.e., 401955.3 km and see what value we get when we divide it by the closest perigee in the years 1750 through 2125, which was 356375 km on January 4, 1912 and as it turns out was very close to being entirely full. So, 401955.3 km / 356375 km = 1.1279 and 1.1279^2 = 1.2722. Drum roll please, (1.2722/1.2696) * 100 = 0.2%. Is anyone impressed? A lot of disclaimer for 0.2%! The question of apparent size relates to the subtended angle of the moon at its various distances and is just the 2 * arc_sin(lunar radius / lunar distance). The lunar distances should be calculated as topocentric distances to be as accurate as possible. My suggestion, ENJOY IT! For a much more detailed treatment visit the following URL: http://www.fourmilab.ch/earthview/moon_ap_per.html Best, Luke
Re: Solstice Perigee
Thanks for the very detailed explaination Luke. So is the answer 27.2% brightness difference between the June Moon and the Dec. Moon? That would mean the paper was wrong. The newspaper also predicted the January Moon would be even brighter (something you didn't cover). Another thing that bothered me is after the astronomical explanation, they author of the article interviewed an astrologer, who basically told him the moon was in Cancer (it may have been another constellation for you sticklers), and the brightness didn't matter. Then he rambled off general predictions depending on your astrological sign. It's hard to believe we are about to enter the 2000s...Frankly, I'm disappointed. No flying cars, and astrologers are still taken seriously. ~Troy
Re: Solstice Perigee
Last night, I was looking at the moon. It was noticibly larger than the night before. This was easy to judge, as it was very close to Jupiter and Saturn which help as size references. These planets look to be about 10 degrees apart. So looking at the moon again tonight, it will be easy to tell about how far the moon moved east in 24 hours. Sorry, don't know the exact declination, except that since the moon is so very close to Jupiter and Saturn, it must be almost on the ecliptic. John Carmichael \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
Re: Solstice Perigee
Roger, I'm not sure of the exact time of Full Moon, but according to my Psion the declination at midnight will be 19deg26min. I hope that helps! John Dr J R Davis Flowton, UK 52.08N, 1.043E email: [EMAIL PROTECTED]
Re: Solstice Perigee
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
Re: Solstice Perigee
In regard to the excitement over the close perigee occuring when the earth is closest to the sun (very close to the December solstice.) My local paper made a comment that the Moon will appear 17% larger than a full moon last summer (that is in June-July for you down underlings), but the full moon in January will appear 40% larger. I suspect it was a misprint, but I thought I'd send it out so you could chew on it. ~troy
Re: Solstice Perigee
almanac lost...there is a program that will do this..i'll see if i can find it 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
