The first choice to make is between plastic or metal construction. Today's low cost metal sextants offer high accuracy and ease of use. These reward the beginner's efforts, and satisfy the professional's demands.
Plastic models are perfect for lifeboat provisioning,and for restricted budgets.
They are also acceptable to some experts who don't mind making frequent adjustments. The following characteristics of sextants should be considered. Older sextants tend to have smaller mirrors and scopes which make them harder to use. Spare parts and maintenance are also more uncertain. Purchase only from someone you know and trust, or a reputable dealer.