While wandering the field at the recent Black Forest Star Party at Pennsylvania’s Cherry Springs State Park, watching groups of amateur astronomers slew telescopes or read star charts, outlined in red light designed to preserve their eyes’ dark adaptation, whispering quietly about what galaxy they were off to observe next or helping someone spot a blurry patch in their telescope’s field of view, I began a new line inquiry. What keeps these astronomers enthralled, I wondered, sometimes for many decades, by the universe as revealed by their telescopes?
(My inquiry will be published here in three parts. In the first, I will try to illustrate how astronomical objects look through a telescope, with a discussion of what makes carbon-based imaging different from silicon-based imaging. The second part will consider what actual amateur astronomers say about what they do. And lastly, in part three, I will attempt to answer the title question with reference to some interesting scientific research.)
What visual astronomers (what we call stargazers that observe the universe primarily with their eyes, augmented by telescopic optics) actually see through their telescopes is far less detailed, colorful and dynamic than, say, what a bird-watcher might see through a similar instrument. And the view through a telescope eyepiece is far, far different from the astrophotographs one sees on the cover of popular astronomy magazines month after month. So what does the universe as revealed through a telescope look like to a visual astronomer and an astrophotographer?
Take, for example, Robert Gendler’s magnificent astrophotograph of M31, the Great Andromeda Galaxy, more massive than the Milky Way and hurtling towards us through space (though it’s 2.5 million light years away so no collision alert klaxons need ring).
Beautiful and stirring as this image is, the human eye could never see Andromeda like this, no matter how big the telescope. Andromeda Galaxy through a typical amateur telescope, seen by the naked eye, is best represented by a sketch. Here is Michael Vlasov’s sketch of the same object:
It’s useful to note that Andromeda is one of the nearest and brightest galaxies that amateurs observe. Most others are far more distant, fainter and show even less detail and structure. Often, even in the largest of amateur telescopes, they appear as faint smudges. I published another photograph/sketch comparison here.
Both images above were made with similar sized telescopes (a foot or under in aperture). The primary difference between the images is a result of the different sensors and processing machines used to create each. Gendler’s telescope was attached to a specialized digital camera and he processed it on a personal computer. Vlasov used his eye and brain to collect and interpret the same data.
The key difference between cameras and computers and eyes and brains is integration time, in other words, how long the sensor can compile an image from the photons it collects. The human eye’s maximum integration time is .2 seconds. In other words, Vlasov’s eye sent an image to his brain 5 times a second. The 40 individual images Gendler compiled into the photomosaic above were “integrated” over 50 hours. The digital camera/computer can integrate for hours, even days. In some cases, like the Hubble Space Telescope, weeks.
So astrophotographers can “see” deeper and farther out into space. The amateur observer has to make do with fleeting glimpses. Unless she is sketching, those faint, ghostly images will exist on the silver screen of the mind.
Being a visual observer of galaxies, I’ve often told crowds before I show them a galaxy through a telescope, is a bit like being a connoisseur of cotton balls. And some amateurs have spent years engaged in thrilling hunts for the dimmest, hardest to see galaxies within reach of their instruments. Certainly it’s not the visual image that thrills them?
We’ll turn next to how amatuer astronomers actually articulate the experience of directly observing the universe. Faith Jordan, a contributor to a thread called “The Joy of Visual Observing” on the Cloudynights forum, formulates the mystery thus: “There’s something about purely looking through the eyepiece…I can’t explain it but there’s a “magic”, for want of a better word, about it that I don’t get when looking at the object on a computer screen.”
What is that magic?