Fiery Pluto said:
The influence of Pluto transiting in conjuction to a personal planet is considered with a maximum orb of 8-10 degrees as Hps. Maxine said in relation to the transits with the major aspects or with a maximum orb of 6 degrees as jos astro indicates?
In natal Astrology it's recommended to use an orb of influence of 8º-10º, as it gives more insight into the chart and helps with interpreting it accurately. As for transits, in order to understand them better, I suggest visualizing them using this graph by astrologer Donald Bradley, which visually expresses the curve of intensity of a transit.
Bradley’s research shows that a transiting planet has the strongest effect when approaching the exact aspect measured in ecliptic length. John H. Nelson, an engineer at RCA Communications, discovered that certain planetary angles, with the Sun at the center, interfered with short-wave radio emissions. The examples illustrating this discovery were planetary aspects with greatly reduced orbs. Nelson specifically stated the importance of the exact or almost exact aspect without having any astrological reference. Though Nelson’s research referred to the heliocentric plane, it is perfectly applicable to a geocentric viewpoint. Nelson’s findings show the maximum influence of planetary transits in an area of between +/- 0º and 1º maximum, measured in arc.
For wide orb transits, the closer the transiting planet gets to the natal planet, the stronger the aspect is felt psychologically and/or physically, coinciding with a major event or change, depending on the planets involved. Normally, the orb that is usually granted for transits is around 5°-6°. In Nelson’s research, he found that 95% of operative transits have a maximum orb of 5º for interplanetary aspects.
In my own experience with longer transits, I have noticed most events occured at around the -2°Applying mark, with some events occuring even at +2°Separating. I am yet to experience a major transit producing events any earlier or later than that. The strongest area of influence for any type of major transit is located between -5º and +5º.
Sources (I also suggest reading this if you want to learn more about transits, I uploaded the book for anyone that wants to read it):
Predictive Astrology 3rd Edition; by Juan Estadella