Don’t Violate Observing Site Etiquette

Rules exist for good reasons. Keep these simple ones in mind when you are observing, and you won’t incur the wrath of your fellow participants.

An observing event can be anything from a large, formal star party with hundreds of participants to a small informal observing session among club members and friends who enjoy spending an evening together under the stars. Whatever the size of the event, behaving properly at the observing site allows you and others to enjoy the session.

A set of (usually) unwritten rules for observing site etiquette has developed. Most of the rules are based on common sense, but some may not be obvious to inexperienced observers. The rules vary with circumstances. If you are observing with a small group of close friends, you can be a bit more flexible. But if you are observing at a large star party, particularly if there are strangers present, it’s best to follow the rules closely. Break a few rules, and you’ll hear others muttering about the newbie. Break too many rules, and you may be asked to leave and not be invited back.

Don’t Show a White Light After Dark

If you remember just one rule, remember this one: do not show a white light after dark unless you have everyone’s permission. It takes half an hour or so for one’s eyes to become fully dark adapted, and a brief flash of white light can instantly ruin that dark adaptation for everyone [Hack #11].

If you must show a white light—and by “must” we mean for something really important, not just a matter of your own convenience—announce your intentions and get everyone’s permission first. Once you have permission (which may be a long time in coming if someone is doing long-exposure imaging), give a timed warning—“White light in 30 seconds…15 seconds…5 seconds…white light is on.” Limit the brightness of the white light—for example, by filtering the flashlight through your fingers—and keep it directed downward rather than waving it around. Finish what you need to do as quickly as you can, turn off the white light, and announce, “White light is off. Thank you.”


Astronomers recognize three types of twilight, each of which occurs both in the evening and in the morning. Evening civil twilight is the period from sunset until the sun is 6° below the horizon. Evening nautical twilight begins when the setting sun is 6° below the horizon, and ends when the sun is 12° below the horizon. Evening astronomical twilight begins when the sun is 12° below the horizon, and ends when the sun is 18° below the horizon. Morning astronomical twilight begins when the rising sun is 18° below the horizon; morning nautical twilight begins when the rising sun is 12° below the horizon, and morning civil twilight begins when the rising sun is 6° below the horizon.

During civil and nautical twilight periods, the sky is still illuminated, and dark adaptation is not an issue. Dark adaptation starts with the beginning of astronomical twilight and is usually complete or nearly so by the end of astronomical twilight. Between the end of evening astronomical twilight and the beginning of morning astronomical twilight, the sky is as dark as it gets. Courtesy mandates using only red lights from the end of evening nautical twilight to the beginning of morning nautical twilight.

Arrive Before Dark

Schedule your arrival early enough to leave plenty of time to set up your equipment before full dark. If possible, plan to arrive at the observing site before sunset, but in no event should you arrive after the end of astronomical twilight. By then, everyone will be fully dark adapted, and some people may be imaging.

Plan Ahead When You Park

Access to observing sites varies, as do the rules for parking. Often, you can pull your vehicle right up to the observing area or pad. (We work directly out of our SUV at such sites.) Sometimes, you’ll have to park at a distance and carry your equipment to the site. Whatever the arrangement, think about what you’ll do if others are still observing when you want to leave.

Many astronomy clubs have specific rules, such as parking face-out so that you don’t need to put your vehicle into reverse and thereby illuminate your backup lights. Depending on the peculiarities of your own vehicle, you may have to modify your actions. For example, our Isuzu Trooper SUV cannot be shifted into gear without depressing the brake pedal first. Although the brake lights are red, they are very bright. Accordingly, we try to point the rear of the SUV away from the observing area. Similarly, some vehicles with automatic transmissions cannot safely be left in Neutral, and must be shifted into Park. To shift from Park to Drive, you must pass Reverse, which illuminates your backup lights, if only briefly. Even that brief flash of white light is enough to ruin others’ dark adaptation.


If you plan to leave when others are still observing, consider parking your vehicle temporarily while you unload, and then moving it far enough away from the observing site that you won’t disturb anyone with your lights when you start your vehicle. Yes, that means you’ll have to carry your gear to your vehicle when you tear down and pack up, but that’s better than ruining everyone else’s enjoyment.

Avoid Using Headlights After Dusk

Although you should always attempt to arrive at the observing site during daylight, if you must arrive after the end of nautical twilight, avoid using your headlights. Depending on circumstances, it may be acceptable to enter the observing area with your parking lights on. If in doubt, turn all of your lights off, walk into the observing area, and ask politely for a volunteer to lead you in with a red light.

When you depart, never use your headlights until you are well away from the observing site. Even the reflection of headlights is sufficient to ruin dark adaptation. Depending on circumstances, it may be acceptable to use your parking lights as you leave the observing site. At large, formal star parties held at dark sites, even parking lights are often forbidden. In that case, find a volunteer to lead you out using a red light. When you reach a safe point, give the volunteer at least a minute or two to get clear before you turn on your lights and ruin his night vision.

Dark Adapt Your Vehicle

If you observe frequently with others, consider modifying your vehicle [Hack #45].

Don’t Crowd Others

When you set up your equipment, have consideration for those who are already set up. Leave plenty of space between you and those on either side of you. In addition to the scope itself, people need room for chart tables, chairs, and so on. In particular, giant Dobs need lots of working room, so if you’re setting up near one always ask the owner if you’re too close. (If you don’t know what a giant Dob is, don’t worry. You’ll know one when you see it.)

Be Careful in the Dark

Particularly at very dark sites, be careful when you are moving around. You may be negotiating what amounts to an obstacle course in the dark, and there’s a lot of expensive equipment at risk. Even if you are using a red flash-light, it’s easy to walk right into someone’s tripod or trip over a cable. Newbies sometimes keep silent for fear of appearing stupid, but experienced astronomers don’t hesitate to ask, “Is there something here I might trip over?”

Conversely, do everything you can to help others avoid tripping over your own gear. If you are running power cables to your vehicle, for example, route them as much as possible out of traffic paths and tape or stake them down. Affix reflective tape to mounts and similar items, or install dim red LED flashers. When people approach your equipment, tell them what’s in their way and use your own red flashlight to guide them around your gear.

Ask Before You Touch

Part of the fun of an observing session is having the chance to look through other people’s scopes, try out each others’ eyepieces and other accessories, and so on. But always ask before you touch anyone else’s equipment or change anything about the setup. Treat other people’s equipment as though it were your own. If you borrow an eyepiece, filter, or other accessory, return it promptly. If someone offers you a view through his scope, accept it, but tread lightly. Don’t hog the eyepiece, and don’t move the scope to a different object without getting permission first. If you don’t know how to refocus the scope or keep it on the object, ask. Politeness counts.

Use Headphones for Music

You may think country-western (or rap, or rock, or classical) is the only type of music worth listening to. Others may disagree, sometimes vehemently. If you must listen to music while observing, use headphones to keep your music private.

Have Consideration for Others If You Smoke

The issue is not the smoke itself. Even non-smokers seldom object to someone smoking outdoors. The issue is the light produced when you light your cigarette, pipe, or cigar. When you light up, turn away from other observers and screen your match or lighter to avoid damaging their night vision.

Some clubs ban smoking entirely at observing sites. We think that goes much too far. Done properly, smoking need not interfere with others’ enjoyment of the evening. However, if you are observing at a site that bans smoking, either honor that rule or find a different observing site.

Avoid Alcohol

Many clubs ban all alcohol consumption at their observing events, based on past unfortunate experiences. We certainly don’t object to someone drinking a beer or two, but we avoid alcohol when we are observing. We suggest you do the same, whether or not it is banned by policy. Even moderate alcohol consumption severely hampers your ability to dark adapt and increases the risk and severity of hypothermia. Heavy alcohol consumption is a very bad idea when there is a lot of expensive equipment set up in the dark, not to mention a risk to your own safety [Hack #3].

Leave Young Children and Pets at Home

Unless young children and pets are specifically invited to an event, leave them at home. Many astronomy clubs run events specifically for young children, but only children old enough to be responsible—at least 10 or 12 years old—should attend general observing events.

It’s always a bad idea to bring pets to an observing site. Even the best-behaved animal may misbehave when surrounded by strangers in the dark, and the last thing you want is to have Fido lift his leg on someone’s tripod, or worse, spot a bunny, take off in hot pursuit, and knock over someone’s scope.

Don’t Be a Moocher

Come prepared with everything you need to enjoy the observing session, including—in addition to your equipment—warm clothing, food, warm drinks, and so on. Don’t count on others to provide things you forgot to bring. Give as good as you get. If someone offers you a view through his scope, return the favor. If someone shares his coffee with you, offer him some of your munchies. If you borrow an eyepiece from him, offer him one of yours to try. Those who take and never give quickly become unpopular.

Have Consideration for Others’ Time

Most amateur astronomers are social animals. They’ll happily offer their scope to anyone who wants a look. But there are times when someone may be occupied, perhaps hunting down an elusive object or setting up an imaging session. If someone is clearly busy, don’t bother him.

Don’t Criticize Others’ Equipment

You may have an $8,000 Starmaster Dob or a $5,000 apo refractor, but that doesn’t give you the right to badmouth other people’s equipment. We have seen some truly abominable behavior in this regard. At one public observation session, we watched a guy go from scope to scope, “star testing” them without asking permission and then telling the owners how bad their scopes were. (We would have bet this guy couldn’t have run a star test to save his life, and the seeing that night was nowhere near good enough to judge much of anything.)

After you have looked through someone’s scope, the proper response is “very nice” or something similar. If, and only if, the owner asks you for your opinion of his equipment should you say anything at all critical. Even then, be gentle. The guy may just want reassurance rather than an honest opinion. If it’s truly clear to you that the owner wants you to be critical, then give him your honest opinion.


We make only one exception to this rule. SCTs and Newtonian reflectors are very often poorly collimated. Many inexperienced owners have no idea that their scopes ever need to be collimated, let alone how to do it. We’ve seen some that were so badly misaligned that they produced truly poor images, much worse than the potential of the scope.

Miscollimation is easy and quick to fix, so it is a kindness to make some non-judgmental remark, such as, “It looks like your scope got knocked out of alignment when you set up tonight.” From there, it’s an easy step toto offer to collimate the guy’s scope for him, and teach him how to collimate while you’re doing it [Hack #40].

Police Up Your Trash Before You Leave

Many club observing sites are on private property, and it’s critical to maintain the goodwill of the property owner. But whether the site is on private or public land, your goal should be to leave the site at least as clean as you found it. Carry a trash bag or container and carry away everything you brought in. If others have littered, pick up their trash as well.

Never Leave One Vehicle Alone

If only one other vehicle remains when you’re ready to leave, wait until you can leave together. We admit that we sometimes violate this rule, but never at remote observing sites and never if the remaining person is a woman. Flat tires, dead batteries, and other breakdowns are distressingly common. If one vehicle is left alone, the results can be at best inconvenient and at worst tragic [Hack #3].

Do a White-Light Check If You Are the Last to Leave

If you’re still there when the last group is ready to pack it in, your final step before leaving should be to do a white-light sweep of the area to make sure nothing is left behind. (We’ve found eyepieces, charts, and, in one case, even an entire telescope that someone had forgotten to pack up.) In small groups, someone will generally know to whom an item belongs. If you find an overlooked item at a larger event, contact the event organizer or the club president to make sure the item gets back to its owner.

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