A Little Earthquake for Siderealists (Gary Duncan)

[Guest guest]

, Therese Hamilton

<eastwest@s...> wrote:

> (LONG POST WARNING)

>[snip]> -------------------------------

>

> " Bradley and I did not agree on all matters. One topic which served

to

> bedevil us still, and which looms as a nasty specter over the most

recent

> determination of the SVP, is concerned with the use of geocentric

latitude

> versus geographic [the latitude listed in atlases] latitude.

Bradley chose

> to use the former for reasons which were, to this author [Duncan]

totally

> unjustified.

>

> " Unfortunately, the evidence and logic support the use of geographic

> latitude, in my opinion. The ramification of this statement may not

be

> immediately apparent to the reader. Final determination of the value

> assigned to the SVP (for the epoch 1950.0) rests in the use of

certain

> mundane charts, the progressions of same, and upon their erection

for

> specific locations upon the surface of the earth.

>

> " In several critical areas, planetary positions near the horizon

are used

> and the chart " rectified " by adjusting the value of the SVP in

order to

> bring about exact conjunction with the desired angle. The reader

will

> appreciate that several factors will affect this calculation. The

specific

> value for the terrestrial latitude used, whether or not parallax

factors

> were used, whether height above or below sea level was considered

both for

> parallax effects and for " dip " of the horizon, whether refraction

of light

> due to the Earth's atmosphere was considered, and whether light-time

> aberration was included.

>

> " Most of these effects were ignored. If any or all are included,

the value

> assigned to the SVP will be immediately affected. **It remains for

future

> generations to re-examine the calculations leading to the

determination of

> the SVP in light of these considerations and to formulate any

additional

> experiments which may be necessary to make further refinements in

this

> area. But, sufficient evidence now exists as to cause genuine

concern that

> the SV) value will someday have to be adjusted.** (page 81)

> -----

>

> So there we have it, ladies and gentlemen. According to Gary

Duncan, the

> SVP is not so sacred as not to need questioning and further

research by

> 'future generations.'

>

> Sorry to rock the boat a little. After all, this is Gary Duncan

speaking,

> who worked many long months (years?) beside Donald Bradley, and not

the

> words of the troublesome lady on the Sidereal board. We now have

wonderful

> research tools because we live in the age of computers. It's up to

*us* to

> test and refine the ayanamsa value.

>

> Sincerely,

> Therese

-----------------

Therese and List,

 

Before you blow Gary Duncan's statement too far out of proportion, I

think you need to understand the differences he was talking about.

Bradley favored using Geocentric latitude; Duncan favored using

Geographic latitude. Several posts ago I pasted Solar Fire's

definitions of the difference between the two. The maximum difference

between the two is 12 minutes of terrestrial latitude, as shown in

this table: (taken from Mary Austin's " Sidereal Calculation Tables " )

 

{The table I had here just totally got screwed up so I've deleted it.

MQ}

 

So a latitude given as 42 deg 12 min geoGraphic would become 42 deg 0

min geoCentric.

A practical example from the SF Quake chart:

The ASC using geoGraphic latitude =24 Pis 56'56 "

The ASC using geoCentric latitude = 24 Pis 53'21 " .

 

In the rainfall data the difference would show in the calculation of

planets' rising and setting times.

With examples taken again from the SF quake chart, as calculated by

Solar Fire 5. (Sorry these did not transfer more clearly)

Planet Geographic rise Geocentric rise Declination

Moon 16:49:11 16:48:55 -12 d 25'

Sun 19:09:14 19:09:00 +10 d 37'

Mercury 18:21:53 18:21:56 +02d 17'

Venus 19:53:50 19:54:11 +15d 35'

Mars 20:19:58 20:20:24 +18d55'

Jupiter 21:11:41 21:12:10 +21d00'

Saturn 17:21:25 17:21:14 -08d48'

Uranus 13:55:41 13:55:08 -23d29'

Neptune 23:19:48 23:20:19 +22d19'

Pluto 22:34:16 22:34:35 +15d18'

 

Using the greatest difference above, from Uranus 33 seconds in rising

time or Local Sidereal Time, let's look at what 33 seconds of time

means in solar or lunar motion.

Using a solar motion of 1 degree per day, 33 seconds of time = 0 deg

0' 01.375 " of longitude

Using a lunar motion of 13 degrees 06 minutes per day, 33 seconds of

time = 0 deg 0' 18.0125 " longitude.

 

So we are not talking any HUGE difference in SVP here between

Bradley's calculations and what Gary Duncan preferred. From the

examples above, which are not in any way atypical since the

declinations range quite a bit from the minimums, we're looking at a

difference of MUCH LESS THAN A MINUTE of longitude or so in the SVP.

 

BTW, the article Therese quoted is available in sidereal.zip in the

Ayanamsa file.

 

Sidereally yours,

Matthew