Sorry for butting in
Why is a horary chart unreadable if there's Saturn in the first house?
This is a stricture against judgement developed around the 13th century and found in Bonatti and later horarists such as William Lilly; the idea is that since Saturn is an "essential malefic", its placement in the originating house of the chart (the 1st house) spoils the chart and makes the delineation of that chart unreliable.
We do not find this "Saturn in the 1st" stricture, in earlier horary astrology, nor in Vedic horary (prasna); also, many practitioners and some authors over the past 50 years or so, discount this doctrine entirely and do not follow it.
One issue overlooked in this question, is the CONDITION of Saturn in that first house: may I follow many others, and point out that IF Saturn is essentially dignified (ie posited in its own signs or in the sign of its exaltation) in that first house, then how could it be a malefic spoiling the chart??
I myself reject the Saturn in the 1st stricture, entirely; I also reject the concept that it appears to be based upon, viz, that Saturn is always a malefic: often Saturn can be the greatest benefic, depending upon its exact situation/condition in a given chart.
I do follow ONE 1st house stricture vs judgement, and that is where the South Node is rising in the ascending sign: based upon my understanding of the SN as always (under any and all conditions) generating disruption and chaos, when I find this influence there in the originating house of the horary chart (1st house), then I consider that chart made unreliable for delineation by the SN in the first. But, for me, Saturn in the first, does not render a horary chart unfit or questionable, for delineation...