You've never really peeked in a telescope before--you climb up a ladder to look in the eyepiece. Visions of grandeur flash through your head. This is a monstrosity of a scope. Your heart wants to burst as you take your first glimpse at a distant galaxy.
And...oh? That's it? That gray fuzzy blob?
Some things are spectacular, every time. Saturn defies rational thought. The moon's sharp shadows creeping over craters is a monthly delight. Jupiter's Great Red Spot, the polar caps of Mars, and the mesmerizing blue of Uranus can make an observer's night. If you gaze beyond our solar system, however, save the Kodachrome. Everything's bettter in black and white.
For some of us, though, the faint fuzzies have it.
Stargazing, like
sex, is mostly between the ears. With experience, the brain gets better at subtle distinctions; what is imagined coalesces with the
rods firing now which blends with the pattern of images seen the past few moments.
A quick glimpse at a deep sky object will look like a faint fuzzy, a wisp of gray. No true color, no distinct boundaries. You fiddle with the focuser knob, the fuzzy fades in and out of view, but it nevers gets sharp on first glimpse. If you do not expect this you will be disappointed.
Keep looking, though, it will get better. A few minutes will improve the image dramatically. A few years will allow you to pick out things you would have thought you imagined the first few times you looked. The line between vision and imagination blurs.*
Several factors play a role, and clearly some things need yet to be learned. Still, when a wizened observer 15 years older than me sees something I cannot, even though my eyes be a bit younger, I no longer doubt him. I grumble about having the vision but not the eyesight--
youth is wasted on the young--but you cannot have both. It takes years to learn how to see, and the eyes give out long before the vision is perfected.
Dark Adaptation
Getting acclimated to the dark boosts your seeing. Your eyes become dark adapted if you stay in the dark for more than a short while. Your pupils will become maximally dilated after a few minutes, allowing more light to reach the retina. (Youngsters have a huge advantage here--young adults can dilate their pupils to about 7 mm, middle-aged adults to about 5 mm.)
Even after your pupils maximally dilate, chemical changes occur in the retina that make you more sensitive to low-level light. The cones become more sensitive within 10 minutes, but the cones not much use looking at the faint fuzzies (though a big help looking at the planets).The rods have significant physiologic changes within a half hour, but may take as long as 2 hours to reach maximum sensitivity.
Averted Vision
The greatest concentration of rods in the retina lies in the periphery of the retina. Rods lack color sensitivity and sharp resolution, but make up for it with increased sensitivity to light. A single photon can stimulate a rod to fire. Deep sky objects tend to be quite faint, and usually lack defintion, making averted vision the ideal way to view them.
How do you do it? Do not look directly at the object. Practice! Your eyes will want to look directly at the object. Stargazers learn to scan the edges of their vision. I do not mean we scan the outer eges of the visual field in the eyepiece; rather, you train yourself to concentrate on the periphery of your vision.
A fun demonstration of averted vision is looking at NGC 6826, the "Blinking Nebula"--when looked at directly, the nebula "disappears". When glanced at sideways, it comes back. As you scan you eye across the field, the nebula appears to blink.
Stargazers teasingly refer to another's averted imagination when someone sees more than others--indeed, it is dificult at times to know where vision and memory diverge.
The insidiousness of the danger of preconceived ideas cannot be over-stressed. One should be prepared to see literally anything, and, ideally, each time an observation is made that does not surprise one, one should immediately be suspicious and on one's guard against a visual datum suggesting more than it in fact states.J.B.Sidgwick
Fortunately for me, I am not a scientific observer. Some nights I trust only my
fovea, and see nothing; other night, the most peripheral of vision reigns, and I see more than I can imagine. I write in my
journal what I see--what else can I do?
Still, when I look at the few sketches I have done, I must admit that I'd be hard pressed to distinguish one faint fuzzy from another. Why the thrill?
Sometimes my spine tingles because of the pure physical beauty--on the rare night of fantastic viewing, the
Great Globular in Hercules shimmers with distinct streams of stars. A picture cannot do it justice.
Other times, I get a small glow from seeing something I should not be able to see. In the Ring Nebula rests a tiny star, with a visual magnitude of 15--very, very faint. I should not be able to see it under urban skies. One night, I caught it. Just once.
Most of the time, though, catching a faint fuzzy resonates because I know that the photons hitting my eye traveled a long, long way. Photons from Andromeda traveled for about 2 million years before I caught them. 2 million years. What creatures roamed in my neighborhood then? What will Earth look like when the photons leaving that galaxy now reach us 2 million years from now? Which of the millions of stars in that immense galaxy gave up this photon that lit up this rod on this night?
One night in late October, I caught Andromeda naked eye--it's the furthest I have ever seen, and likely will ever see, without a telescope.
And I smiled in the darkness.
* There have been instances when particularly astute observers have seen things thought physiologically impossible, then confirmed by photography. Stephen James O'Meara saw better as a teenager than I ever will, no matter how long I live..
While still a teenager, O'Meara saw and mapped radial "spokes" on Saturn's rings that professional astronomers dismissed as illusory--until Voyager reached Saturn and confirmed that the spokes were real. He determined the rotation rate of the planet Uranus, obtaining a value wildly at variance with those produced by professionals with larger scopes and sophisticated detectors, and proved to be right about that, too.Timothy Ferris, Seeing in the Dark
Sources:
J.B.Sidwick, Amateur Astronomer's Handbook, Dover Publications, 1980
Timothy Ferris, Seeing in the DarkSimon and Schuster, 2002.
Distance to the Nearest Galaxy, The Physics Factbook, http://hypertextbook.com/facts/1999/SaraLi.shtml
Observing Tips, The Big Sky Astronomy Club, http://www.glacieradventure.com/StarGaze/ObservingTips.htm