This is a system of brightness of stars, that was used in the second century BC, it was a method of dividing the stars into 6 groups, the brightest being the 1st magnitude and the faintest being the 6th magnitude. All that was done without a telescope. But today magnitude is relevant to what can be seen in a telescope. In astrology the brighter the star, the more power it has, this is why often only the brightest stars and those lying on the suns path are ever taken into consideration by an astrologer.
Also each star has a colour, and this is another form of classification, the colour shows not only the temperature but where it lies on the main sequence. The colours of the stars also likened to the planets, and their associated attributes to the planets of similar colour.
