Until the 17th century, astrology and astronomy were twin subjects, and were taught alongside at the great - now oldest established - universities of Europe. Astronomy was more scientific, and was concerned with understanding how the heavens worked; astrology was more philosophical and was concerned with relating the movements of the heavenly bodies to our experience here on earth. The basic tenet was "As above, so below".
Then astrology fell from prominence as science took over, scientific knowledge grew and expanded, and astrology became something of the poor relation, open to ridicule and scorn as it could not be scientifically proved. On the plus side, this is changing, as scientists worth their salt are admitting that some things simply cannot be explained scientifically (Richard Dawkins doesn't fall into this category!).
Any astrologer who is serious about their study will have a good working understanding of our Solar System. Students on the APA Foundation Courses have to do some basic astronomy as part of their training; the twin subjects can't be separated out.
Although I'm not deeply conversant with astronomy, I'm certainly interested in it and have a good understanding of how the birth chart and the Solar System relate to each other. Last week I took a trip to the world famous Jodrell Bank Observatory, home to the Lovell Telescope, the first ever radio telescope. I've visited it many times to see the orrery spheres of the solar system on display, and to enjoy the visual trips to various planets in the planetarium. I was there last week because we had a visitor staying who has started to study astronomy, but I'm always up for a trip there as I find the telescope itself an inspiring and awesome structure. It's visible from many areas of the county where I live and acts as a homing landmark. It's even been featured in a dramatic episode of the TV series "Dr. Who".
In 2007, Jodrell Bank celebrated its 50th anniversary. It was threatened with closure but this threat was averted and more recently it's visitor centre and adjacent arboretum has had a makeover.
Whilst I was at Jodrell Bank I saw a 3-D film about the Sun through the special 3-D viewing specs the audience were provided with. Before the film started, we were told that the commentary was now "wrong" as there are now 8, not 9 planets in the Solar System. Pluto was demoted a couple of years ago and is now classed as a dwarf planet. My hackles only rose slightly at this, because I've yet to meet an astrologer who has stopped using Pluto when they set up a chart! The film was interesting, and the info sheet handed out at the visitor centre gives a good website - The Nine (Eight!) Planets - for those who want to learn more about the planets in our Solar System.
You can see the chart for Jodrell Bank in the post I wrote in August 2007 when it celebrated its 50th anniversary.