For the last few months, Ms. Doane and a few colleagues, along with volunteers from the Amateur Telescope Makers of Boston, have been setting the stage for a mammoth attempt to bring the entire collection into the digital age. The result, if money can be found, will be more than just an archive. Digitized with a custom-crafted scanner already in operation, the searchable online atlas will ultimately show any spot in the heavens as it appeared from the late 19th century to the mid-1980s — an astronomical Wayback Machine.

“Nobody has ever systematically looked at the sky on 100-year time scales,” said Josh Grindlay, the Harvard astronomer in charge of the project. “There is this whole dimension that hasn’t been explored.”

Walking into the plate stacks, housed in a brick annex on the observatory grounds, is itself like a trip back in time: the dimly lighted rows of green metal cabinets separated by little more than a shoulder’s breadth, the light tables on which the plates are mounted for inspection with a magnifying loupe, the shelves of old ledgers in which astronomical observations were recorded with fountain pens. All of this is housed in a repository resting on a slab of concrete extending down toward bedrock, with the interior of the building, a cage inside a cage, structurally decoupled from the exterior walls.

“The thought was that in an earthquake the two would shake independently,” Ms. Doane explained. “As data goes the plates are pretty sturdy and the collection in good shape. But they are glass and if not used gently, of course they can crack. Murphy’s Law will guarantee that your star will be on the crack when you go to look at it.”

For years it was rumored that the base of the building rested on leaf springs like those in an old pickup truck. In search of the truth, Ms. Doane crawled, flashlight in hand, down through a trapdoor and into the foundation. No springs in sight, just spiders.