Skyscript Astrology Forum

Hello Deb/Margherita

How about 'Ptolemaists Reunited'?

Its hard to see how western astrology could have developed the influence it did without Ptolemy's contribution. I know there are some hard core hellenistic astrologers who wish to diminish the importance of Ptolemy. However, this is next to impossible considering his historical influence. Astrology was given a large amount of respectibility simply because the author of the Almagest and Handy Tables also wrote about astrology. It gave astrology an entrance into sophisticated intellectual debate it would never have had otherwise.

I dont think astronomy or astrology took a 'wrong turn' as Kirk suggests. Far from it. The Almagest was a significant achievement. All the Arabic astronomers I mentioned earlier closely studied Ptolemy's work. The fact they were able to significantly improve on his astronomical findings is a testament to their ingenuity. However, they all did so with the help of Ptolemy's prior work. Thus to paraphrase Newton they were standing on the shoulders of a giant too see further. Clearly, no science operates in a vacuum. Ptolemy heavily relied on Hipparchus while Hipparchus made extensive use of Mesopotamian astronomical recordings.

Still at the risk of being labelled a Ptolemy basher and being cast into astrological Tartarus I do think its interesting to study some of the astronomical deficiencies in the Almagest. It helps reveal some of the problems with his Star Catalogue. Here is an article by the American astronomer Owen Gingerich entitled 'The Trouble with Ptolemy'.

http://www.jstor.org/pss/3080419

As its a JSTOR article its only free for those with University access. Despite the article title it is a good deal more respectful to Ptolemy's astronomical contribution than the ridiculous hyperbole of Robert Newton.

Owen Gingerich knows what he is talking about, but it's a defence of Ptolemy (abstract below).

Mark, do not bring us informed accounts, which we are then obliged to spend time reading. Bring us more of the uninformed biased rubbish, so we can make quick rants without having to think about things.

Hello Deb,

There is already a whole website entitled Cafe Astrology. So I suppose there is room for a 'cup of tea' thread.

Just to get your blood boiling Deb/Margherita and allow you both the opportunity for full rant mode I should tell you Robert Newton has been publishing more on Ptolemy....

The Origins of Ptolemy's Astronomical Parameters by Robert R. Newton.......$16

Newton's 228-page typeset monograph is an outgrowth and amplification of a previous study entitled The Crime of Claudius Ptolemy. It addresses the paradox that, while the parameters that Ptolemy claimed to have derived from his astronomical observations are apparently accurate and, in Newton's view "bear some resemblance to reality," his purported observations appear to be, for the most part, fabrications. Rather than attempting to uncover the sources of Ptolemy's values in specific historical observations prior to his time, Newton attempts to explain Ptolemy's rationale in dealing with his astronomical parameters and calculations on the basis of an analysis of the mental processes involved. [ISBN 0-912025-02-6]

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The Origins of Ptolemy's Astronomical Tables by Robert R. Newton...........$16

In this 264-page typeset companion volume to The Origins of Ptolemy's Astronomical Parameters, Dr. Newton analyzes the tables that Ptolemy states he calculated from these "fabricated" observations and concludes that they were in large part copied from now-lost tables of the ancient Greek astronomers rather than having been calculated from observations made in Ptolemy's time. Of special interest is the chronological sequencing of the original tables based on the level of mathematics involved in their calculation. [ISBN 0-912025-03-4]

Get your orders in now: http://terpconnect.umd.edu/~tlaloc/arch ... apubs.html

Deb wrote: It might not have been obvious that I was being ironic, sorry.

Deb

But I understood this, mine was a more general thought...I never will be able to write things put so well like you.

p.s but definetely yes Ptolemy was perfidious with Venus and Mercury epycicle..

margherita

There is already a whole website entitled Cafe Astrology.

I took a look. It's a nice site. However, I ran a search and the only links that related to Ptolemy required me to buy a personality profile report.

Here are some online calculating tools to convert from equatorial to ecliptical and vice versa. I remember that someone mentioned them a year ago and found the website by chance last week.
http://www.antonblog.net/tools/
http://www.antonblog.net/tool/coordinates.html

MarkC wrote: How about 'Ptolemaists Reunited'?

If I had to choose between Ptolemaists Reunited and FC Hellenistics then I'd go for the Ptooligans.

Deb wrote:(I like this thread because it allows me to express annoyance with the whole world, and no one in particular. I'm going to check it everytime I have a teabreak and keep adding little ranting comments.)

Deb

I always go here http://www.verbon.biz/ .

Hi Mark,

thank you very much for your detailed answer to my question of possible errors in Ptolemy's star positions.

Please don't forget to start the thread "Paranatellonta . . . " some day.

Hi Mark,

thank you very much for your detailed answer to my question of possible errors in Ptolemy's star positions.

Please don't forget to start the thread "Paranatellonta . . . " some day.

Indeed. Although Margherita is really the authority on the traditional basis of the Paranatellonta here.

I just think there is quite a lot of confusion out there which is leading many people to assume Brady's methods are identical with the traditional Paranatellonta.

Not wanting to doubt the authority of margherita or any other member of this forum - only it was your idea, Mark, to compare Brady's and the real traditional technique of paranatellonta.

Here are some online calculating tools to convert from equatorial to ecliptical and vice versa. I remember that someone mentioned them a year ago and found the website by chance last week.
http://www.antonblog.net/tools/
http://www.antonblog.net/tool/coordinates.

Hi Eddy:
I know this is now an old thread but I was reading exactly on the same subject that motivated it: the Brady?s book. Mark caughts my attention into this thread and then I saw your reference on the coordinate?s conversor and it really drew my eye.
I had one doubt, though: when we convert the equatorial coordinate to the ecliptic one, we give the RA and the declination,okay? Well,I did it, using Spica , that is more or less at 23? of Libra
The RA was 13? 32? and the declination -10?52?
The program gave me (in ecliptic coordinates) a longitude of 8? 6'
What this means? The difference between Equator and ecliptic coordinates? Initially I thought that it was referring to ecliptic longitudes departing from 0? of Aries, but it was impossible, since Spica can?t be in Aries. At least not now!
I agree with Mark?s concerns, and I was trying to figure out if the result using Equator coordinates would give a so big variety comparing to Ecliptic coordinates. If the difference was not be so big it would be useful to give a larger orb to cover both systems.
Thanks in advance for your attention!

Clelia

Hello Clelia,

Hopefully Eddy will reply to your post. However, in the meantime I just wanted to state that I recently used that coordinate calculator/convertor myself to plot the ecliptical position and latitude of a comet. I was initially very confused as I had calculated the Comet's postion was around 26? Taurus near to the fixed star Algol. However, I got a figure nowhere near that. The reason was that I had failed to convert the equatorial coordinates to hours and minutes first. Instead I was dealing with decimal coordinates. You need to do that first before you can enter the star or comet position into the coordinate calculator. Could that be at the root of your problem? Plus the result you get from the calculator doesn't give you the sign just the postition along the zodiac with the beginning obviously 00 as Aries. Hence my comet position in Taurus was listed as simply 56?.

If its any use to anyone here is a calculation method I got from the web. Although Eddy had already given me the basic formula to convert between the two systems of equatorial coordinates.

Right Ascension is traditionally measured in hours, but degrees are a common alternative that is being seen more frequently in modern times. A complete circle of 360? is equal to 24:00 hrs of right ascension.

The fact that a sidereal day is equal to 23:56 hours of solar time is irrelevant to this discussion. A sidereal day is equal to 24:00 hrs of sidereal time.

Now to solve your RA problem. I'll assume you are using a handheld calculator, and will provide the simplest algorithm for that case.

Lets use an example of 66.918277?. Divide that by 15. The result is 4.461218467. The truncated integer value of 4 is the number of hours of RA.

Multiply the fraction 0.461218467 by 60. The result is 27.673108. The truncated integer value of 27 is the number of minutes of RA.

Multiply the fraction 0.673108 by 60. The result is 40.386, which is the number of seconds of RA.

Therefore, 66.918277? of RA equals 4:27:40.386 hrs of RA.

Remember to distinguish between northern and southern declinations by preceding the numerals with (N or S) or (+ or -).

Eddy mentioned another important point in a PM which I am sure he will not mind me sharing here:

Note that the astronomical ephemerides are set for a so called epoch http://en.wikipedia.org/wiki/Epoch_(astronomy) in the table you linked to you can see 'RA (2000)'. The positions are set for a date (usually 50 years apart) so astronomers don't have to make a new starmap every year. So what you do when you converted to longitude/latitude is converting to 2010 as if it were sidereal to tropical chart. For years after 2000 you add the number of years divided by the rate of precession which is about 72 years per degree (or rather 71.583). In the example it would be about (for the middle of the year 2010) 10.5/72 = ca. 0.15? = 0?9'.

Hope this helps,

regards

Mark

Hi Mark!

I printed your explanation, only to see that I wrote it wrong in the message : Janus gave me the RA in hours and not in degrees.
BUT your hint was important since that what I have to do is to transform the hours in degrees, since the coordinates Eddy sent use degrees instead of hours.
Now I?ll do exactly the opposite: at the moment you said to divide I?ll multiply.

I?ll try it and i?ll let you know!

Thank you a lot!

Cl?lia