Posted by: Donna Cunningham | October 23, 2009

How to Make Sure a Birth Chart is Accurate

 (c)2009 by Donna Cunningham

Before you begin to interpret someone’s birth chart, ask yourself the most basic question of all—how accurate is the birth time? The birth time is the key to such crucial parts as the Ascendant (also known as the Rising sign or first house cusp), the Midheaven (the career point at the top of the chart), and the signs on the cusps of all twelve houses. Rounded-off times like 7:00 or 7:30 are suspect.

Times on the quarter hour—7:15 or 7:45—are likely to be closer to true, and a time like 7:06 could be exact. You need to know, also, whether you are talking about 7:30 AM or 7:30 PM, since they are 12 hours apart and usually six Rising Signs different, and yet that part of the birth certificate may be blurry.

Estimating the Accuracy of the Birth Time

babybook-webAsk where the person got the data. If it’s from Mom’s memory, she’s 80, and she had seven kids, it’s iffy, unless memorable circumstances accompanied the birth. A birth announcement or baby book should be given some credence. If the time was noted on the birth certificate, it is at least as close as the delivery room staff could make it.

Be especially cautious when the Ascendant is in the last few degrees of one sign or the first few degrees of the next, since a slight difference in birth time could change the rising sign. In borderline cases, ask the Sun sign of both parents, as one of them may be the correct Ascendant.

owever, when difficult planets like Saturn, Pluto, or Neptune fall near the Ascendant, inquire if any unusual circumstances accompanied the delivery. Often there is quite a saga, and if this was a chaotic (Neptune) or a particularly difficult birth (Saturn or Pluto), the data could well be in question.

Especially in life-threatening circumstances, delivery room staff are paying attention to the baby and the mother, not the clock on the wall. Typically, when both stabilize and cleanup begins, someone will ask when the baby was born. The person in charge looks at the clock and vouches a guess, and that guess is recorded for posterity.

Also take the birth place and year into account. Until 1967, observance of daylight savings time was notoriously changeable from town to town and even year to year, especially in the Midwest. The best reference is The American Atlas, available in both digital and hardcopy format, but even that is amended as new information comes to light. (San Diego, CA: AstroComputing Services 1981)

Pesky Pennsylvania–the Bane of an Astrologer’s Existence!

In some areas–and some eras–state law mandated that standard time be used on the certificate rather than daylight time. Illinois was such a state until 1959, as was Pennsylvania between 1921 and 1970. Where the rule was in effect, the birth certificate of someone born May 25th at 9:00 PM EDT would read 8:00 PM. Not all hospitals paid attention to the law–and not all delivery room staff remembered it all the time. So, even the time on a birth certificate may not be recorded correctly.


For Pennsylvania and Illinois natives, definitely ask where the time came from. A baby book or birth announcement notation may be based on clock time and thus might be daylight savings. A parent’s memory of the birth time may be from the clock (and thus Daylight Savings Time) or may be from a later glance at the birth certificate (and thus possibly Standard Time).

For DST births, ask for a few key past events, to double-check the Midheaven through transits or progressions. Despite precautions, errors creep in, but at least you’re forewarned.

That’s bad enough, given that there are 186 time tables for Pennsylvania in The American Atlas. At least six months of the year, we don’t have to worry about daylight savings time–except for those born during World Wars I and II and the oil crisis of 1974-5. However, just when I thought it was safe to fire up the software, I discovered that if Pennsylvanians find a town name they like, they tend to use it more than once.

 I surveyed one two-page spread–two of 26 pages of towns in Pennsylvania. Among the many redundancies were two Bethlehems, two Bryn Mawrs, three Bloomingdales, five Brooksides, and SEVEN Bridgeports. (There may also be North and East Bridgeport and Old Bridgeport–they wouldn’t be listed on that page.) Also watch for spelling variations–there were two Bridgetons and one Bridgetown.

The towns are often far enough apart to produce several degrees difference in Ascendants and Midheavens. Between the two Bethlehems, there are three degrees difference on the Midheaven and four on the Ascendant. That is enough to throw predictions off seriously or change a rising sign. To avoid error, ask the county of birth or nearest good-s

brooklyntattoo-webized city. (Pennsylvania isn’t the only problem area–there are three Brooklyns in New York state. Two are in the boonies a considerable distance from New York City, but the one where so many bright, funny, famous and infamous folks were born is 73W56; 40N38.)

What can you do if the birth time is suspect?  There is a site on the internet where you can order copies of your birth certificate. Be sure, however, to specify that you want the LONG FORM, which more often has the time inscribed, and, to be absolutely certain, indicate that the birth time is what you want to know. The link to the Internet site is:

HC how2readcvr sm

 NOTE: This is an excerpt from Donna’s hardcopy book,  How to Read Your Astrology Chart: Aspects of the Cosmic Puzzle. .  To order a copy of the hardcopy or Kindle book, call the publisher, RedWheel/Weiser, at 1-800-423-7087 or order from


  1. Donna, nice site etc. Could you do us a favor and rectify Obama’s chart based on events in his life? I was on some site where a woman left a message that she had gone to the trouble to do this with Obama and came up with a chart that gave him TAURUS RISING. I sorry to report I can’t pull that site up at this point. I will look.
    I don’t care if Obama was born elsewhere or not…he does have an American mother…but I do not like that we may all be using the WRONG chart for him..thanks

    • Hi, Suzy, since I have nothing but Neptune in Virgo, I’m not really a fan of the process of rectification, which can involve days of painstaking work, so I’ll pass. I’m perfectly satisfied with the chart corresponding to Obama’s birth time given on the birth certificate online. That’s Aquarius Rising, not Taurus. Donna

      • I buy Aquarius rising for Obama hands down. He really fits it and he’s got the Aquarius mole on his face.

  2. Looked up some taurus risings : Bobby Darin, Humphrey Bogart. Aquarius risings: Tom Selleck, Jim Morrison (The Doors)

  3. Hello,

    Good information as always, Donna.

    I would like to add that, in my experience, way more birth certificates are wrong than are right. I have gotten into the habit of rectifying all charts that I do for natal clients. One of my most recent clients gave me a window of time for her birth from 10:30 to 11 am. When I rectified the chart (using the Polaris rectification software), I got a birthtime of 10:26:14, which was before the period she had given, but close! When she came, I mentioned that I had rectified her chart and the first thing that she mentioned was that she had found out that she was really born 3 or 4 minutes BEFORE the range of time she had initially given.

    Rectification is always WORK, so far there is no fully-automated process that works. The closest that I have found is Polaris. One basically enters in the events for a person’s life (in the example above I had over 15 events) and the search range and the program (mainly) uses Topocentric Primary Directions to find the most likely birthtimes and then lists those. At this stage, using other methods, the correct time can be discerned.

    I was originally quite skeptical, but Isaac’s program CONFIRMED my “20 year rectification in progress” (6:16:44) during the first evening with the program. To me, that was impressive. The birth certificate (and newspaper article about my birth) both listed 6:18 am. Quickly, I realized that 6;17 was closer. Over the years, I shaved a second here or there, driven basically by an anal-retentive Pluto in Virgo in the 3rd. 😉

    The more events you have, the higher up the list the correct birthtime floats. The larger the search range, of course, the more events you need. Additionally, when you DO have a birth certificate with a seemingly exact time, you can use a very small search range and not so many events and narrow that time down to the second.

    The real thing that convinced me of this program was when Susan Boyle became an overnight sensation and everyone was scrambling for a birthtime. (a Scottish astrologer later was able to obtain the birth certificate) In the meantime, Isaac had used his Polaris program and rectified her chart using a handful of events from Susan’s life and posted the birthtime. Later, the birth certificate time confirmed Isaac’s rectification, as the two were 38 seconds in difference.

    The birthtime is the “initial cause”,…it is the key piece of information that ALL of our subsequent “findings” flow from. Any error there has the potential to propagate down the line.

    The other “fringe benefit” is that there is more confidence in the birthtime…since it was derived by finding a time that WORKS astrologically to the Events.

    For anyone that is curious about the method. The program takes the time of the search range and slices it into thousands of pieces. Each one of those “pieces” is evaluated (with Topocentric Primary Directions) relative to the events and SCORED IN TERMS OF TIGHTNESS OF ORB AND SYMBOLIC APPROPRIATENESS OF ASPECT TO EVENT. The possible birthtimes are listed in terms of weighted score. The more events that are available, the higher up the list one finds the correct birthtime.

    As I said, it STILL requires work, but the software is a Godsend compared to the old way of trying to discern the angles by suspected aspect activity. (which was often frustrated by relocation factors)



    • Thank you so much, James! What a valuable summary. And, yes, having worked for a number of years in prenatal clinics as a social worker, I would not be at all surprised if even a birth certificate is often wrong. There’s too much going on in a delivery room in terms of the welfare of mother and infant for the staff to make recording the time a priority. But a birth certificate time generally beats a parent’s vague memory. Donna

  4. Hi there,,
    I’m new to this blog, though not to astrology. The summary about rectification is very thought provoking……I am one of the many whose time of birth was rounded up to the hour or half hour, though I did ask my mother when she was alive and she said she was sure it was 11.30 a.m.
    I have meditated on this to see if I can get a sense of what “feels” right and came up with11.27.
    However I would love to have this checked out in the rectification process and wondered whether you know of anyone who does this professionally.
    I have just downloaded the Stellium handbook and am finding it interesting and so far, easy to read and digest, so thank you Donna!

    • Hi, Maria. I don’t know anymore who does it, as the good ones I knew are all older now. You might try putting “astrology chart rectification” into the search engine on Google and see what astrologers come up.

      Meantime, work on a list of important events in your life, and pinpoint the year, and as close as possible the date they occurred. Some but not all of the transiting planets on those dates could be aspecting the Midheaven or Ascendant. Then match the degrees of the transiting planets to the degrees on the angles at 11:30 and at 11:27. You may at least be able to see if those degrees are in the ball park. Donna

  5. Hi,

    My birth time is supposedly 12:10PM which is Libra but if it were 5 minutes later, 12:15PM, it would be Scorpio. My mom’s sun is Libra and my dad’s sun is Scorpio. I don’t really feel like my rising is Libra because I’m very much an introvert except for the occasional social gathering. Is it possible to be a mix of both? What should I look at for more help? Thanks


    • Hi, Katie, birth times at the end or beginning of a sign on
      the cusp are often inaccurate. Trust your feeling.


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