Thisis a great sextant for any navigator of any ability. Beginners won't break the bank buying it and experienced navigators will enjoy it for back-up, treaching, and emergency use. Regardless of what anyone says this sextant is plenty accurate enough for serious navigation. Check out David Burch's book regarding the Davis MK 3. He is as respected an authority as you will find on the subject of celestail navigation and his comment is that most people who claim it isn't accurate enough for real navigation simply don't have experience using it. I was 100% in agreement with that assesment even before he published his book on the Mk 3.
My own experience with this sextant is that under decent conditions I regularly get inside of 2 nm, which is pretty good for cel-nav. No one, not even with very expensive fancy metal sextants, gets inside of 1 nmi on a regular basis. I own a bunch of fancy metal sextants (I'm a bit of a collector) and this little plastic gem holds its own with the best of them (Freiberger, C. Plath, Tamaya...)
It is simple and rugged, which makes it easy to pack along. It is easy to adjust. It is lightweight so you won't get fatigued doing a complete round of sights. It is inexpensive so you won't bust the buget on a sextant and find yourself short of funds to buy a Nautical Almanac, plotting instruments, sight reduction tables, plotting sheets, and all the rest of the kit absolutely necessary to tackle the learning process including instruction books and star charts. BTW get yourself a hard copy of The Nautical Almanac too. A real must have for learning celestial. Digital versions just don't cut it for learning your way around the information contained therein.
Teh Mk 3 makes a great back-up sextant to a fancy metal sextant on those days when the spray is flying and you would rather not risk your C. Plath or Tamaya to a salt water dousing.
Later on, if you stick with cel-nav and treat yourself to a fancy metal sextant, you will still keep this one around for emergency, back-up, and for teaching others who might be curious.
IMHO this sextant is far superior to the more expensive plastic sextants that are made to look like metal sextants. Those are notorious for not getting repeatable results. If you are just starting out they will frustrate you and leave you wondering what it is you are doing wrong... and those sextants are not particularly inexpensive! This Mark 3 is a much better choice over those in every respect. I know. I owned one of those too and it was a nightmare while this simple MK3 is a delight.
Get a big Tupperware box to use as a waterproof case.
If you learn just a little about the stars you will never be truly lost, with or without a sextant and a bunch of books! Get this sextant, get a hard copy of The Nautical Almanac, get out there, and enjoy!