A: Thank you for your question! What you don't mention is "where" you have always been reading about the differences between the Chart Ruler and Ascendant Ruler. I'm always curious where to find differences of interpretation because it does help me to better understand different ways of interpreting concepts. But, aside from that, I can tell you where to find similar definitions that I used on my site and also explain where I believe the confusions could be coming from.
Different astrologers put different meanings to astrology terms because of the various types of astrology being used in so many different languages. Also, I note that a lot of new Astrology terms are developing on the Internet. Over time, meanings change as do the terms being used. The definition I use for "Chart Ruler" on my site concurs with the definition found in "The only astrology book you'll ever need," by Woolfolk, and "The only way to learn astrology" by March & McEvers, as well as any number of other astrology books and websites across the Internet. The books I referenced are both basic and great resources for beginning astrologers. Sometimes I see "Chart Ruler" referenced as "the ruling planet of the chart." Some astrologers call the rising sign's ruling planet the "Significator." But I believe that this term comes more from the vedic. I believe that Paul Wade, "Be your own astrologer," simply calls the ruler of the ascendant as "the ruling planet." How confusing is that? But that's also an accurate way of describing it.
The term used for a planet that rules over a person's "sun sign" (or any sign) is called the **planetary ruler**, hence many astrologers logically conclude that the ruler of the rising sign of a chart must be the **chart ruler.** Yet, what is so different between the terms Ruling Planet and Planetary Ruler?
For example, (as explained by Dane Rudhyar, "The Astrology of Personality," page 496),
"The first way of singling out a planet, to make it serve as a center of significance, is to find what is called the 'ruling planet' or 'ruler of the chart.' This is usually determined by the sign of the Ascendant. The planet ruling this sign becomes the ruler of the whole chart. The rationale of this method is clear. The Ascendant represents the factor of individual self-hood, the monad, the fountainhead of the life and destiny which the chart as a whole symbolizes. Therefore the planet functionally dominating this Ascendant becomes naturally the dominant life-function of the personality. However, in the case of planets rising close to the Ascendant, or when a planet, wherever situated in the chart, 'disposes' of all or most other planets, then two or more planets may divide the honors of chart-rulership."
Additionally, the term chart ruler being used as I have on my site would also be called the "ruler of the first house."
Other terms that are frequently confused and misused are Rising Planet, Ascending Planet, Scout Planet, Leading Planet and Oriental Planet. The term for the planet closest to the ascendant moving the opposite of the numbers on the houses (i.e. 2nd, 1st, 12th) is usually called the Rising Planet or the Ascending Planet. Many astrologers believe that the closeness of the planet to the Ascendant makes the planet more influential.
"Rising planet: A planet considered to be close to the ascendant. As with all else in astrology the deciding number of degrees will vary by astrologer, but within 5 degrees on either side of the Ascendant cusp being a widely accepted orb."
"A planet above, and within 5°, of the eastern Horizon."
"Oriental - literally eastern; said of a planet that rises and sets before the Sun. "
"The oriental planet, called the leading planet, is the one that will rise immediately before the Sun; i.e., the planet that directly precedes the Sun clockwise (behind the Sun in the natural order of the zodiac)."