In the 1930's a French Anthropologist by the name of Marcel Griaule studied the Dogon people for several years. It is from the results of his research that all of the supposed astronomical knowledge of the Dogon people is based on.
There have been several scientific articles published about the findings of this anthropologist. The Dogon myths seem suspiciously accurate and the sources are not conclusive. In fact, although the star Sirius B wasn't actually observed until around the 1970's, scientists thought that it had existed since the 1880's.
A widely accepted theory is that Marcel Griaule stretched his actual findings in order for them to include Sirius B, when actually, the Dogon myths may have made no reference whatsoever to such a star.
Much of Griaule's findings are based on the accounts of only a few people in the Dogon community. Griaule met with several Dogon priests in long sessions during which he talked with them. Because of the length of these sessions and the fact that he did not seek other Dogon sources to back up any claims, it is entirely possible that his information is faulty.
Unfortunately, it will be difficult to find the truth about the Dogon myths for several reasons. Firstly, much of the information found today on the Dogon people has been distorted by Griaule's findings. Secondly, Dogon mythology was never written down, but has been passed on through oral tradition. Lastly, the Dogon people are limited in number, and there are numerous different versions of the myths that vary from community to community.