Probably your best bet is to find a copy of Bowditch also known as the American Practical Navigator or H.O. 9 which used to sell for $23 and was the best bargain you'll every get from the feds. Unfortunately the Gov't Printing Office does not have them in stock which probably means a new edition is in preparation. The second best choice is probably Dutton's Navigation and Piloting (nearly as complete as Bowditch) ISBN: 0870211579 which you can get from Barnes and Noble for about $70. For a survey of what a sextant is, what it does and how to service and adjust it (but not so much on how to use it) get a copy of Bruce Brown's "Sextant Handbook" ISBN: 0070052190, about $15 in paperback. For a simple guide to the use of the sextant for navigation get a copy of Mary Blewitt's "Celestial Navigation for Yachtsmen." ISBN: 0070059284, about $13. You will learn that you need tables for sight reduction (conversion of sextant sights to lines of position). Probably the simplest to use are H.O. 249, "Sight Reduction Tables for Air Navigation" although the larger and more expensive H.O. 229 "Sight Reduction Tables for Marine Navigation" is the standard on large ships. You can order these from the GPO by going to http://www.access.gpo.gov/ and clicking on the "U.S. Government Online Bookstore" then searching for the title above. There are computer programs and small programmable calculators which will automate the process, eliminate mathematical errors (but not the other errors we are all prone to) and fail when you need them most so get at least H.O. 249. Another advantage to H.O. 249 is that Vol. 1 has precomputed star sights. I find star sights pretty difficult but presetting the expected altitude and pointing in the right azimuth (both from H.O. 249) makes the job almost simple. Celestial is lots of fun. Enjoy.