Chart Rectification using Secondary Progressions
Here's a quick example of chart rectification using secondary progressions.
The first image is of a bi-wheel horoscope. The inner wheel is a natal chart for Tony, born on 29th Feb 1964 in Wakefield, UK at 01:30hrs.
The time is wrong. We can be fairly sure of this because the secondary progressed chart is the chart for his wedding day (18-Oct-1996) and the planet Venus is a few degrees from making a conjunction with the descendant of his natal chart. Because this event is very close and because this is Tony's only marriage, we can conclude that the time of the natal chart may be out by between twenty and thirty minutes
The second chart is for the day Tony relocated from Northern England to Southern England 08-Jan-1999. Because progressing Jupiter is close to being in the right place for such a move (in opposition to his progressed Midheaven - and therefore conjunct his progressed IC - the home part of the progressed chart), but not quite, we can conclude that the natal chart is out by some minutes.
After a little calibration, we find that if we change the time on the natal chart from 1:30am to 1:10am, the wedding chart is corrected - progressing Venus has now passed over the Descendant of the natal chart - a wedding configuration.
And suprisingly, the same adjustment creates an accurate configuration in the relocation chart, where Jupiter is exactly opposite the progressed Midheaven.
It was confirmed later - by Tony's mother - that this time was more realistic. 1:30 had been an approximate time.
So that's how you use progressions to rectify a natal chart...