WASHINGTON, Jan 27 (Reuters) - New orders for key U.S.-made capital goods increased for an eighth straight month in December, pointing to solid growth in business spending on equipment in the fourth quarter and likely helped to underpin economic recovery. Orders for non-defense capital goods excluding aircraft, a closely watched proxy for business spending plans, rose 0.6% last month, the Commerce Department said on Wednesday. These so-called core capital goods orders advanced 1.0% in November. Economists polled by Reuters had forecast core capital goods orders rising 0.6% in December. (Reporting by Lucia Mutikani; editing by Jason Neely)