The phrase 'may observe' is correct and can be used in written English.
It is used to express possibility or permission. For example, "Visitors may observe the ongoing research study."
"In me you may observe fit punishment," the severed head helpfully points out.
Under latter-day legend, one may observe in dusty gilt "Mouquin".
(Drunken party behaviour, you may observe, rather than life-changing self-reinvention).
Visitors may observe themselves and others while reflecting on architecture and the structuring of everyday life.
It is hard but it is necessary, and the PM may observe one of life's ironies: with failure comes opportunity.
"We are precluding some, and there are many, who may observe Saturday as their sabbath," he said.
Alpine tourists may observe marmots, which live in the high meadows, and chamois.
(The scribes included 2/3, one may observe, even though it is not a unit fraction).
Anyone who has had the good fortune to interview notables of the French movie business may observe that even those of international prominence live surprisingly normal lives.
Other things in the world we may observe and engage.
As settlers assimilate and become familiar with the new environment, they may observe something interesting.
