Calculating or Estimating the MC by hand

[parintachin5`]

Hi,

Let's say you don't have access to a computer, but you do have access to an empheris, know the person's rising sign, and want to draw up charts. How do you calculate- or even get a good estimate- of the person's MC?

[Fluffmeister]

Hi,

Let's say you don't have access to a computer, but you do have access to an empheris, know the person's rising sign, and want to draw up charts. How do you calculate- or even get a good estimate- of the person's MC?Yes - this one's quite easy (guessing the Ascendant is much more difficult!).

If someone was born at local noon, then the Sun will be conjunct the MC. By "local noon", I mean when a sundial would say it's noon. In the Eastern USA for instance, 12:00 EST will be local noon at a longitude of 75W. The Sun takes 4 minutes to travel a degree westbound, so if you live at 80W but are still on EST, when the TV says it's noon, it won't be local noon for another 20 minutes. If you're on daylight savings time, you'll need to subtract an hour - when it's noon, your clock will say 13:00 (1pm).

Having worked that out, the MC moves one sign every two hours (this is why the Ascendant is much more difficult - in the northern hemisphere at the latitude of London, UK, Aries rises in about 40 minutes, but Libra takes 3 hours to rise. Fortunately, the MC is better behaved than this!). This is a very good approximation, but may be a few degrees out.

So the steps are as follows - I'll use two examples, one really easy one and one trickier one.

First, the easy one - someone born in Greenwich, London, England (51N32, 0W00) at 15:00GMT on 15 March 1960:

1. Make a note of the person's birth time - if it's daylight saving time, subtract an hour. It's GMT, no daylight saving, so don't subtract anything.

2. Now work out local noon. Each "time zone" is pretty artificial - there's only one place of longitude where local noon is the same as clock noon. For each hour difference from GMT, that represents 15 degrees. I chose Greenwich for this example because "Greenwich Mean Time" is the same as local time. So local noon is 12:00 here.

3. Now work out the difference between local noon and the birth time: in this example, the birth time is 3 hours after local noon. The MC moves 30 degrees in 2 hours, so in 3 hours it will have moved 45 degrees.

4. So, the MC must be 45 degrees after the Sun. On 15 March any year, the Sun is at about 25 Pisces - so 45 degrees after that is 10 Taurus. So the MC is about 10 Taurus.

OK, that's the easy example. Now let's choose a more realistic one: someone born at 07:00EDT on 15 August 1980, in Cincinatti (39N10, 84W27).

1. Make a note of the person's birth time - if it's daylight saving time, subtract an hour. It's EDT, daylight saving, so they were actually born at 06:00EST.

2. Now work out local noon. Each "time zone" is pretty artificial - there's only one place of longitude where local noon is the same as clock noon. For each hour difference from GMT, that represents 15 degrees. EST is 5 hours behind GMT - that's 75W. Philadelphia is on this line of longitude pretty much (so local noon is the same as clock noon), but Cincinatti is about 10 degrees west of this line. In fact, Cincinatti would be closer to sundial time if it was on CST instead of EST - but political boundaries don't obey sundials! So if it takes the Sun 4 minutes to move 1 degree, it takes the Sun an extra 40 minutes to move 10 degrees. So local noon in Cincinatti is not 12:00 but 12:40.

3. Now work out the difference between local noon and the birth time: in this example, the birth time is 06:00EST, and local noon is 12:40EST. So this person was born 6 hours 40 minutes before local noon. The MC moves 30 degrees in two hours, so it would move 90 degrees in 6 hours, and 10 degrees in 40 minutes. So the MC is going to have to move 100 degrees between the birth time and noon.

4. So, the MC must be 100 degrees before the Sun. On 15 August any year, the Sun is at about 23 Leo - so 100 degrees before that is 13 Taurus. So the MC is about 13 Taurus (in fact, it's about 17 Taurus).


Of course, once you have the MC, you can find the Ascendant using a table of houses.

[Fluffmeister]

If you know their rising sign - you don't need to do the maths at all. Just use a table of houses - look up the Ascendant (the table of houses usually has a page for each degree of latitude - so for Los Angeles, look up the table of houses for 34 degrees North), and you can read off the MC directly for any given Ascendant.

[KEishin]

Well, except you really shouldn't do it the last way - IMHO. The first one Fluff posted is great except the sideraeal time is missing. The Midheaven doesn't change as much based on latitude as does the Ascendant, so make sure you are using the TCST (Total Calulcated Sideral Time). If you don't add in the sideral, it'll screw things up. Remember that the sideral "clock" gets reset each year at 0 Aries.

I've attached a pdf of my chart calculation technique using a midnight ephemeris from a class I taught. I hope this can help you. Scroll to the top of the second page and look for the header for:
"To find the MC, IC, Asc or Dec using a table of houses (not correcting for latitude)"

(I also have a noon version available -PM me if you'd like that one instead)

[parintachin5`]

Wow. Okay, thanks :) It's going to take me a while to figure that out and get comfortable but awesome, thank you.

[Bryony]

Sometimes it is easiest when learning to look at a finished example, then work backwards...

[Fluffmeister]

Well, except you really shouldn't do it the last way - IMHO.

I didn't make it very clear in the post, but I mean if you know the actual Ascendant you can look up the MC directly without needing to know sidereal time. For instance, if I tell you my Ascendant is 27 Leo and my latitude of birth was London, then a table of houses for London only has 27 Leo appearing on one line - this one:

Sid Time: 02:54 MC: 16 Tau Asc: 27Leo22

So the only possible MC is 16 Taurus (which is indeed my MC). The sidereal time happens to be 02:54, and no other sidereal time has that particular Ascendant, so that's why I can look up the MC directly. If I didn't know either my Ascendant or my MC, then yes - I'd need to work out sidereal time and look it up. But if you know your Ascendant to the nearest degree, you can use a table of houses to look up the MC directly.


The first one Fluff posted is great except the sideraeal time is missing. )
Yes, but it's a very good approximation and works without having to have access to a table of houses. If you do have a table of houses *and* an ephemeris then you can use the sidereal time to work out the Asc and MC to the nearest degree (my method doesn't need a table of houses or ephemeris, but is only accurate to within 3 or 4 degrees).

For anyone who's thinking "what's sidereal time??" I've got a simple explanation in my article on chart calculation here: http://www.bristolastrology.net/chrismitchell/ascendant.html

[KEishin]

I didn't make it very clear in the post, but I mean if you know the actual Ascendant you can look up the MC directly without needing to know sidereal time.Ah, I see now. That *is* a great way to approximate, but again, only if you know the Ascendant by degree and arc minute. Thanks for clearing that up Fluff. As you said, it may be off by as much as 4 degrees, but for most people, they don't need precise measurements - they just want their sign.

Of course, I'm into precision when casting (my Virgo decante strikes again :smileroll), which is why I do the full shebang. Last I checked, I have five tables of houses on my bookshelf at home. Yes, I'm an astrology geek. :)

If anyone needs an online ephemeris or table of houses, they can be found at these links:

http://www.achernar.btinternet.co.uk/campanus.html <---- Please note, the Table of Houses is Campanus only (which is not very common) but should give the general process to those wanting to practice until they can buy their own copy in a more common house system. I have yet to find other house tables online for free.

And of course for ephemerides, there is always Astrodienst. http://www.astro.com/swisseph/swepha_e.htm

[Fluffmeister]

http://www.achernar.btinternet.co.uk/campanus.html <---- Please note, the Table of Houses is Campanus only (which is not very common) but should give the general process to those wanting to practice until they can buy their own copy in a more common house system. I have yet to find other house tables online for free.


I was commissioned to produce a Placidus table of houses for a publishing company a couple of years ago. The final format I did for them is of course their copyright, but I own the copyright on the "raw data" as it were - and I'm happy for these HTML tables to be freely used and distributed for non-commercial use. The tables and instructions are available here:

http://bsa.bristolastrology.net/course/tables_of_houses.html

Basically, all the HTML tables are zipped - and the zip file includes a TrueType font called "Star Font", which you will need to install to be able to view these tables sensibly (without it, Aries to Virgo appears as the letters x c v b n m and Libra to Pisces as X C V B N M instead). The starsans.TTF file is included in the Zip file - this font is available on various websites, so I'm pretty sure it's public domain (if anyone knows differently, please let me know!)

[KEishin]

Excellent! Thanks Fluff.
Wow, calculating your own house table - that's no small matter. :fpraise:

[Fluffmeister]

Excellent! Thanks Fluff.
Wow, calculating your own house table - that's no small matter. :fpraise:Houses are quite easy, really - although curiously, even though it's an old system, Placidus is the most complex of all to calculate (in computing terms, you have to "iterate" - it involves taking a first guess at a house cusp, then plugging that value in and refining it). It's not difficult with a computer, but I pity the medieval astrologers who had to do it by hand!

The mad thing is that there's a program out there that will calculate Placidus cusps for you - it's part of the excellent Swiss Ephemeris (from www.astro.com (http://www.astro.com)). If you're writing one for non-commercial use, you just write a program that calls the Swiss Ephemeris - et voila! There's your table of houses.

However, because this was for commercial use, it would have involved paying a licence fee; the publishing company had no objection to this, but wouldn't accept some of the other terms and conditions attached to it - so in the end, I reinvented the wheel and wrote the program from scratch. After all, no one owns the copyright on the algorithm itself, which is over 500 years old!

Subsequently, I did an ephemeris for them as well - and told them we were back to the licensing issues if we took the Swiss Ephemeris route. It occurred to me that there was one other body who can provide ephemeris data - NASA. I told the company I reckoned they'd charge a fortune, but let's ask anyway - and NASA e-mailed me back very quickly indeed saying their data could be used publicly without charge (even for a commercial operation, which this was), which was a nice surprise!

Now, Keishin - as I know you're a fellow maths geek, you might like this particular website on the NCGR site which gives all the formulae for house calculations :) Warning to anyone else reading who *hates maths* - DO NOT click on this link! ROFL!

http://geocosmic.org/articles/astrohouse.php?fileref=includes/housemain.shtml#overview


Anyone interested in why there are so many house systems, but isn't geeky enough to want to know the maths, this excellent article by Deborah Houlding is worth a read:

http://www.skyscript.co.uk/temples/9.html

[KEishin]

OoOOoh! :bouncybob
You know how to make a girl's heart go pitter-patter :smoochypo

btw Fluff: are you part of the NCGR? I've been considering joining the chapter near me in Boston, but have been dragging my feet a bit.

[Fluffmeister]

OoOOoh! :bouncybob
You know how to make a girl's heart go pitter-patter :smoochypo
LOL!! :bigredgri


btw Fluff: are you part of the NCGR? I've been considering joining the chapter near me in Boston, but have been dragging my feet a bit.No, I probably would join if they set up a UK chapter - it's a great way of meeting other astrologers. I'm a member of the Astrological Association of Great Britain, which has links with NCGR.

Incidentally, Bernadette Brady (my favourite astrologer) is giving a talk on Saturday 26 March in Boston (I've posted details below, but check out http://geocosmic.org/chapters/chapters.php?ChapterIdx=15&submitChapter=Go+ for more info):

ANNOUNCEMENTS AND UPCOMING EVENTS:
The Boston Chapter of NCGR presents:
Bernadette Brady, Saturday, March 26, 2005

10 AM to 4:30 PM—Belmont Public Library
336 Concord Avenue, Belmont, MA

Title:
The Daemon and Its Dreams: Insights into the Question of Profession

WORKSHOP
One of the many questions we are asked in the consulting room is to find the potential profession of a chart. But this is not a modern question, as the subject has been discussed in astrological writings for nearly 2,000 years.

A chart has what can be thought of as your daemon, the dream within you which pulls you towards lifestyles, interests and your profession. By looking at some medieval concepts in astrology, valuable insights can be gained into the likely preferred professional pathway of the horoscope. Bring your own chart.

[KEishin]

I know! I saw that . . . and hoping to go.