If Burnham, who kept so assiduously to himself, was unsure what impact his books had had on others, he could have had no doubt after the responses to his letter began to arrive.
Wrote one devotee: "I am an extremely grateful and dedicated admirer of your Celestial Handbook, and when I saw your address in Sky & Telescope, I felt compelled to write my appreciation. . . ."
And from other letters: "Could you be so kind as to send me your autograph, perhaps with a short message if you could spare a few moments. I would always proudly keep it with the Handbook. . . ."
"I would like to offer a very large and heartfelt thank you for this wonderful set of handbooks. My dog-eared set is always with me when observing. . . ."
"The text is beautifully written and is almost as enjoyable as actual observation. As a chemist, I can think of no comparable work done or possible in my field. . . ."
"Your Celestial Handbook is considered the Bible among all of my associates. . . . My set holds a revered place in my library. . . ."
"I am on my second set of these books--the first set wore out from heavy use. In my library of over 1,200 books, this set is my most prized possession. . . ."
One writer, Louis Lyell of Jackson, Mississippi, wrote Burnham about an observatory he had helped build at a private school, and about the school's need for an astronomy teacher. The job seemed custom-made for Burnham, who enjoyed talking to young people about science more than anything else.
Lyell says he never got a reply.
Instead, Burnham sank further into bitterness and obsession about money.
Then, in July 1985, he vanished.
Viola Courtney can't be certain what day her brother disappeared. At the end of August, Norm Thomas called to tell her that police were conducting an investigation and had searched Burnham's apartment.
Courtney and her family traveled to Flagstaff that weekend. In her brother's mailbox, she found a letter she had sent to him on July 17, and judging from the pile of newspapers on Burnham's porch, that's about the time that he abandoned the place.
Norm Thomas and Courtney say it looked like the apartment had been robbed, but selectively. Missing were many small items that seemed valuable--shiny artifacts and coins, mostly.
Otherwise, the apartment was filled with the things that had always been there, as if Burnham had left suddenly.
Burnham's landlord threatened to have the contents of the apartment auctioned unless Courtney paid his back rent. She did. And the rest of the weekend, Courtney and her daughter Donna and Michael Bartlett moved the collections and books to a storage unit.
"Robert had sold things, but there was still a lot of stuff in the apartment. Books, books and more books," Courtney says.
"Huge books," says her daughter.
"And rocks. Buckets and buckets of rocks," Bartlett adds.
Then, they set out to find Burnham in Mexican Pocket.
It was a place, Courtney knew, between Flagstaff and Oak Creek Canyon where her brother searched for treasure. Perhaps he had gone there and something had happened, she reasoned.
Courtney and Bartlett went there but found nothing.
Then, just as they were about to leave, Courtney spotted Burnham's VW bus among the trees.
It was locked, and the metal detector was inside. There was no trace of Burnham.
Flagstaff police searched the area in vain. Burnham became another name on a nationwide missing-persons list.
And the people who knew Burnham began to get used to the idea that he might be dead.
Then, about 11 p.m. on September 9, seven weeks after Burnham had disappeared, a Newport Beach, California, police officer noticed a disheveled man walking aimlessly on the beach.
He asked the man's name. "Robert Burnham," the man answered.
Burnham was wearing a long-sleeve shirt and pants, but his feet were bare, and they were covered with second-degree burns from exposure to the sun. He was taken to the hospital for treatment, then released to a shelter.
"He had a beard, he seemed tired. His feet were horrible. But it was him. He acted like he always had," says his niece, Donna Courtney. She lived in San Bernardino at the time, and she retrieved him from the shelter. Then her mother drove out to bring him home to Phoenix.