There is a collection of ≈500,000 sky photographs in the archives at Harvard College Observatory which cover the entire sky from 1890 to 1989
Two independent Johnson B light curves for KIC8462852 from 1890 to 1989 were created from the same set of Harvard plates, the first with 1232 plates with DASCH magnitudes, and the second with 131 plates with my by-eye measures.
The KIC8462852 light curve from 1890 to 1989 shows a highly significant secular trend in fading over 100 years, with this being completely unprecedented for any F-type main sequence star.
KIC8462852 is suffering a century-long secular fading, and this is contrary to the the various speculation that the obscuring dust was created by some singular catastrophic event. If any such singular event happened after around 1920, then the prior light curve should appear perfectly flat, whereas there is significant variability before 1920.
* Star dimming for 100 years with irregular dips in brightness consistent with Dyson swarm construction and orbiting of partial Dyson Swarm
* The star brightness also dipped erratically throughout the four years, sometimes losing as much as 20 per cent of its brightness.
* 100 years of dimming is not consistent with a comet theory
* Some other explanation is for some new unknown stellar process that causes a star to dim over a long time and to have erratic brightness now
The researcher Schaefer is unconvinced. “The alien-megastructure idea runs wrong with my new observations,” he says, as he thinks even advanced aliens wouldn’t be able to build something capable of covering a fifth of a star in just a century. What’s more, such an object should radiate light absorbed from the star as heat, but the infrared signal from Tabby’s star appears normal, he says.
The star KIC 8462852 is a completely-ordinary F3 main sequence star, except that the light curve from the Kepler spacecraft shows episodes of unique and inexplicable day-long dips with up to 20% dimming. Here, I provide a light curve of 1232 Johnson B-band magnitudes from 1890 to 1989 taken from archival photographic plates at Harvard. KIC 8462852 displays a highly significant and highly confident secular dimming at an average rate of 0.165+-0.013 magnitudes per century. From the early 1890s to the late 1980s, KIC 8462852 has faded by 0.193+-0.030 mag. This century-long dimming is completely unprecedented for any F-type main sequence star. So the Harvard light curve provides the first confirmation (past the several dips seen in the Kepler light curve alone) that KIC 8462852 has anything unusual going on. The century-long dimming and the day-long dips are both just extreme ends of a spectrum of timescales for unique dimming events, so by Ockham's Razor, all this is produced by one physical mechanism. This one mechanism does not appear as any isolated catastrophic event in the last century, but rather must be some ongoing process with continuous effects. Within the context of dust-occultation models, the century-long dimming trend requires 10^4 to 10^7 times as much dust as for the one deepest Kepler dip. Within the context of the comet-family idea, the century-long dimming trend requires an estimated 648,000 giant comets (each with 200 km diameter) all orchestrated to pass in front of the star within the last century.
Arxiv - KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989