Hi Jup, eekk an archaeoastronomer,
I agree with some but not with others, i'm dealing with birth charts, i can make a difference in area of RECTIFIED FROM APPROX. TIME OF BIRTH!
For Helena P. Blavatsky, she never knew time of birth, however most astrology sites now put it as 02:17am on 12th August 1831, this is dubious, being Rectified from Approx. Time by astrologers!
For her who was born in a country that followed the Julian Calendar during time of birth we get a date of 31st July 1831, but this is a Julian Date, thus 12 days have to be added, for true accurate interpretation, so as far as i know 12 August 1831, will give a date for astrology programmes!
Time of birth is far more dubious, due to rectified time by astrologers, why choose 02:17am???
Please scroll down to source notes on link below:-
http://www.astro.com/astro-databank/Blavatsky,_Helena_P.
The above doesn't seem to work, but i'm sure you can find it by search engine!
Yes on day in location, Sirius was rising 11 mins 18 secs before Sunrise, but choosing 02:17 am was putting "Muddy Waters" on top, sorry for musical pun, we will never know time of birth for Blavatsky, but choosing 02:17 am is very odd, as ALNILAM WAS RISING!!
Graph on private members download:-