It can be difficult to find an Ashtanga yoga studio in your area, and one with a teacher that you like.
Traditionally, Ashtanga yoga is taught by a very experienced teacher who teaches you the Ashtanga series as you learn, and memorise the asanas. The teacher adds on more positions when the student has sufficiently learned the previous positions.
Thankfully, I have found a wonderful studio that I practice at with amazing teachers. But, when I go back home to visit in Sacramento. I haven't been able to find an Ashtanga yoga studio. I have found a wonderful Hot Yoga studio in Sacramento that teaches Hot Bikram and various Power yoga classes. This is nice because it challenges me in other ways, and gives me a variety, and the teachers and other yogis are amazing people.
There are times that I don't want to go to the studio because I am too busy, don't feel like being around people, but I still want to further my practice. I think Youtube videos, books and blogs can be extremely helpful for times like these.
Anthony Grimm Hall is a self taught Ashtanga Yoga teacher who has an interesting yoga journey and proof that you can, in fact, teach yourself Ashtanga yoga. He has a blog and documents his development.