Astronomers discarded first hand visual observations, because each observer measured a star's transit as occurring at a different time. Physicists soon followed them, so that now instrumental... This description may be from another edition of this product.
ThriftBooks sells millions of used books at the lowest everyday prices. We personally assess every book's quality and offer rare, out-of-print treasures. We deliver the joy of reading in recyclable packaging with free standard shipping on US orders over $20. ThriftBooks.com. Read more. Spend less.