Predictive Techniques: Solar Arc vs Secondary Progression

Solar Arc vs Secondary Progression: Which Systems to Use?

Secondary progression (i.e. “a day for a year” method of directing a natal chart) has been around for a long time, but it was by no means the only method of progressing a horoscope. Throughout the history of astrology, astrologers have invented different methods of projecting a natal chart into the future.

Right now, Solar Arc and Secondary Progression are the most popular methods used by professional astrologers.  Noel Tyl popularized the Solar Arc method (although he still uses Secondary Progressed Moon). There are many fine astrologers using Secondary Progression as their tool of choice, so both methods are here to stay.


Difference between Secondary Progressed and Solar Arc Planets

One of the key differences between the two methods is that in Solar Arc you get to advance the slower moving planets (Saturn through Pluto) that hardly move in the Secondary Progression method, so this tends to add more interpretive possibilities when forecasting.

Noel Tyl, who has written extensively about both progression methods, stated that in our modern era, important life changes (e.g. divorce, job change, relocation, etc) occur much more frequently than in previous times – thus we need a method that more accurately reflects the rapid pace of modern life.

In Secondary Progression, outer planets are pretty much unusable due to how slowly they move.  In Solar Arc, you’ll see natal outer planets located in cadent (3rd, 6th, 9th or 12th) houses crossing an angle within the first 10-30 years of life, frequently representing major restructuring of family unit, home environment, or the profession.


How to Calculate Solar Arc Planets’ Movement

Solar Arc planets “move” at the speed of Secondary Progressed Sun, which is approximately one degree per year.  If you obtain the current location of SP (secondary progressed) Sun, and calculate the arc (angular distance) between the SP Sun and the natal Sun, you have the “Solar Arc” you need to progress your natal chart to its current Solar Arc position (your astrology software will make this calculation for you automatically.)

Even a fast-moving planet like Venus will have a longer time frame (say 6 months applying, and 3 months separating) to be in orb using a Solar Arc method: this means Solar Arc of Venus aspecting the natal Sun (written Venus=Sun) would last for about 9 months, strongly suggesting the success of a relationship or an artistic endeavor.

In transit, Venus moves so fast that it can’t have much of an impact except for a couple days of pleasantness. Similar things can be said of Jupiter, whose transit is fleeting but under the Solar Arc, suggests a 9 months period in which reward or opportunity is likely to be presented.


Testing Solar Arc in Your Own Horoscope

Solar Arc is relatively easy to test in your own horoscope: add 1 degree per year to the natal planets to see how they move and form an aspect with the natal planet. The orb needs to be exact (less than one degree) in order for the Arc to be in effect, and we count hard aspects (conjunction, square and opposition) only.

If natal ASC (Ascendant) is at 12 Leo, and natal Saturn is at 22 Leo, this means Solar Arc ASC will conjoin natal Saturn at age 10 (we write ASC=Sat to denote this period), then we ask if there had been a status change within the family around that age: some Saturnian event such as death in the family, sickness, move, or change in father’s position, etc.


Conclusion: Secondary Progression vs Solar Arc?

Solar Arc is a modern derivative of Secondary Progression that allows the astrologers to utilize Saturn and outer planets more fully in their predictive work.  Many modern astrologers including myself use Solar Arc (which gives central importance to the Secondary Progressed Sun’s movement) in combination with Secondary Progressed Moon (which is a very important timer of life progress.)


A Must Read Reference: Solar Arcs by Noel Tyl

Noel Tyl has written extensively about his method of prediction in Solar Arcs: Astrology’s most successful predictive system. The book is actually a summary of his predictive method incorporating transits, Solar Arcs, Secondary Progressed Moon, as well as Tertiary Progressed Moon.

About Hiroki Niizato

Hiroki Niizato is a professional consulting astrologer in Florida, serving clients in US and abroad. He has been practicing astrology professionally since 2001. Hiroki is a highest honor graduate of the demanding Master’s Degree Certification Course in Astrology by Noel Tyl.

You can contact Hiroki via email at: or Phone: 727-470-4056 to ask a question or schedule a consultation.


  1. Hi Hiroki – Solar Arc Pluto is nearing a conjunction (within 1 degree) to my natal Sun (in the 2nd), Solar Arc Mars just squared (and is still within 1 degree) my natal Venus (also in the 2nd), and Solar Arc Ascendant is almost exactly conjunct my Natal Neptune(where else, but in the 2nd).

    Lately, our financial situation has been challenging, and this has caused me to seriously rethink my “value” to the world, which has been very confusing. If you have any insights as to how to interpret these Solar Arcs, I’d be very appreciative. Thanks very much.

  2. I just took another look, and Solar Arc Uranus just entered my 2nd house several months ago. This 2nd house theme seems to be a recurring one. And in my natal chart, I have a stellium there, which includes my North Node.

  3. Hiroki Niizato says:


    Major measurements like those you listed here suggest a time of profound shift in self perception – at least the opportunity for this is abundantly there, in the form of your current challenges.

    ASC=Neptune is tricky, and is bound to be accompanied by some confusion for a time. Be patient here.

    Best regards,

  4. Hiroki – I will try to follow your advice to be patient as I wade through the Neptunian Fog. In the meantime, I think I'll try to make the best of it by finding an appropriate outlet for my artistic talents. Thanks for sharing your wisdom — I do appreciate it.

  5. Hi Hiroki
    just realised I have SA Neptune 1 degree away from Natal Asc.. is this good?Thanks: Learning so much from your ACES website! ~=}

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