Your first night under a truly dark sky

Sky darkness gets described on the Bortle scale, which runs from 9 down to 1. Nine is the middle of a city, where you can count the stars on two hands and the sky has an orange floor to it. One is the kind of place where the Milky Way is bright enough to cast a shadow and you can see the horizon by starlight alone.

Here is the thing that surprises people: the jump from a city to a genuinely dark site is not gradual. It is not "some more stars." Somewhere around Bortle 4 the sky stops being a black ceiling with dots on it and becomes something with depth, texture and a structure running through it.

That is where I draw the line. Bortle 4 or darker, and I would rather have 3. Below that number the sky is pleasant. At it and past it, the awe kicks up and people stop talking. It is a real threshold, not a preference, and everything else on this page is organised around getting you across it.

I do not take it on faith either. I carry a sky quality meter and measure the sites I write about, in magnitudes per square arcsecond, because a class is somebody's judgment and a reading is a number. The bands in the slider below are my own working chart — including the 4.5 step, which most published tables leave out and which is exactly where a lot of "pretty dark" places actually land.

Finding your own number

You can look it up before you look up. A light pollution map gives you a colour for your address and a colour for anywhere you are thinking of driving, and that is enough to build a shortlist from. I built my own because I wanted the one I would actually use.

It comes with a caveat, and it matters. The satellites behind every light pollution map, mine included, mostly see light going straight up, and they are weak on the blue-white LED lighting that has replaced everything over the last decade. A place can measure better on a map than it looks overhead. Treat a map as a shortlist and your own eyes as the verdict, which is exactly why I carry the meter.

The instinct is to head away from town and pull over when the sky looks good. Two things go wrong. You end up on the shoulder of a road with headlights sweeping you every four minutes, and you have no idea whether the field you just walked into belongs to somebody who will mind.

Pick the place before you leave. In rough order of how well they work:

• Certified dark sky placesParks and communities that have done the paperwork to prove their sky is dark and their own lighting is not wrecking it. They are usually set up for night visitors, which means a place to park and often somewhere to stand that is not a ditch.
• State and national forest landVast, quiet, generally fine to be on after dark, and there is usually a pullout, a trailhead or a boat ramp with a clear horizon.
• Your local astronomy club's observing siteThis is the one people never think of. Most clubs have a site they have been using for decades, they know exactly which nights are good, and they will hand you a look through a telescope worth more than your car. Email them. They are almost always delighted.

What you want on the ground: an open view low to the south, no lights within sight, a place to park that is not a highway shoulder, and cell signal or a downloaded map so you can find your way out.

Three things decide whether a night works. Two of them you can know months ahead, down to the minute. The third you cannot know until a few days before, and it is the one that will cancel on you.

Plan around the first two. Stay flexible about the third.

A telescope shows you a small, magnified circle of sky and demands that you know where to point it. On your first dark night you do not want a small circle. You want the whole sky at once, because the whole sky at once is the thing you came for.

• Binoculars, 10x50 or 7x50Fifty to eighty dollars, and about twenty-five times more light than your eye. Andromeda and the Pleiades stop being dots. The best money in amateur astronomy.
• A red flashlightWhite light costs you half an hour of adaptation in one second. Red barely touches it. Buy a real one; a phone app will eventually show you a notification.
• Something to lie onA foam pad, a reclining chair, a blanket over the car hood. Your neck will quit long before your eyes do.
• More layers than you thinkHat, gloves, a spare jacket. Dew is real and a thermos is not a luxury.
• A planisphere or a star chartA paper wheel you dial to the date and time. No battery, no screen, which is the point.
• A green laser pointerFor showing somebody exactly what you are pointing at. Never near aircraft, and check the local rules first.

Your eyes have two systems. The one you use all day is fast, sharp and sees color. The one that sees in the dark is slow, colorless, and far more sensitive — and it takes time to switch on. Most of the improvement arrives in the first twenty minutes. It keeps going for another twenty or thirty after that.

So arrive while it is still light, get set up, and then simply stay in the dark. Do not check your phone. One glance at a white screen and you are close to starting over. If you must use a screen, red light only, dimmest setting, and pointed at the ground.

The reward is a sky that keeps arriving. Ten minutes in, you have a nice sky. Thirty minutes in, the Milky Way has a spine and dark lanes running through it. Forty minutes in, you start seeing things at the edge of vision that vanish when you look straight at them.

Watch it happen, and then find out what a light costs you.

That is the whole reason for the red flashlight, and the whole reason not to check your phone. Red light barely registers. One careless click of a white headlamp costs you most of an hour you already spent standing in the cold.

Learn averted vision on night one

The center of your retina is nearly blind in the dark. The sensitive cells sit off to the side. So when you want to see something faint, look slightly beside it rather than at it. Faint galaxies and nebulae jump into existence when you do this and disappear when you look straight on. It feels like a trick. It is just anatomy, and it is the most useful thing a beginner can learn.

Here is a strange thing nobody warns you about: a genuinely dark sky can be disorienting. The constellations you know are buried in thousands of stars you have never seen. People who can find the Big Dipper from their driveway lose it entirely at Bortle 2. That is not a failure. That is the point.

Start with the biggest things and work down.

One more thing worth doing on a first night, because it reframes everything else you are looking at. Every star you can see is at a different distance, and the light hitting your eye left each one at a different moment in history. Some of it left before you were born.

A recent phone in night mode, propped against something solid so it cannot move, will pull the Milky Way out of a dark sky. It will not be a great photo. It will absolutely be a photo that makes somebody say "wait, you saw that?"

A camera with manual controls on a tripod does considerably better. The starting point is the widest lens you own, the aperture all the way open, ISO somewhere around 3200, and a shutter long enough to gather light but short enough that the stars stay round — for a wide lens that is usually somewhere between ten and twenty seconds. Focus manually on a bright star, at maximum magnification on the screen, and check it after your first frame. Autofocus will not work and soft focus ruins everything.

If you want the deep-sky objects rather than the landscape, that is where a smart telescope comes in — you set it on the ground, tell it what to look at from your phone, and it stacks its own images while you carry on looking up with your own eyes. Which is the right order.

Whatever you shoot, take five minutes at some point in the night with no camera, no phone and no plan. Lie back and let it be enormous. That is the part you will actually be describing to people in ten years.

Every photo below is one of mine, taken on an ordinary night from somewhere you can legally stand.