text: Lasby taught astronomy and mathematics at Mount Holyoke College during her graduate studies there. She was hired as a computer at Mount Wilson Observatory in 1906. She was the first woman research assistant at Mount Wilson, starting a few months before Cora G. Burwell joined the same department. In 1910, she attended the fourth conference of the International Union for Cooperation in Solar Research, when it was held at Mount Wilson. She left Mount Wilson in 1913, after co-authoring several scientific publications, including a monograph with Walter Sydney Adams. She became a member of the National Association for the Advancement of Science in 1921.
  In 1914, Lasby went to work on a spectroscopy project in Germany, but she returned the following year with the start of World War I. She worked briefly at Goodsell Observatory in Minnesota, and was a librarian at Northfield, Minnesota.
  From 1919 to 1946, Lasby Tessmann taught history and astronomy at Santa Ana Junior College. She helped develop the Bishop Observatory in Orange County as a teaching facility. She spoke to community groups often, and was president of the City Teachers League and the Business and Professional Womens Club, both in Santa Ana.