How to use a telescope: your first night

8 min read

Key facts

Cool-down time	About 30–60 minutes, longer for large reflectors
Finder alignment	In daylight, on a distant object such as a treetop or mast
First eyepiece	Lowest power: the longest focal length number
Best first targets	Moon, then bright planets, then the Pleiades
Dark adaptation	About 20–30 minutes; keep only dim red light
Mount types	Alt-az (up-down, left-right) or equatorial (follows the sky's turn)
Reflector upkeep	Check collimation (mirror alignment) now and then
Sun safety	Never point at the Sun without a certified front solar filter (ISO 12312-2)

In short

Set up on firm ground, level the tripod and let the telescope cool to outside temperature.
Align the finder in daylight on a distant object, never on the Sun.
Always start with the lowest-power eyepiece; it shows the widest, brightest view and is easiest to aim.
Begin with the Moon, then bright planets and the Pleiades, before hunting faint targets.
Most disappointing first nights come from too much magnification, a shaky tripod or looking through a window.

Before dark: set up and let it cool

Pick a spot on solid ground, such as grass or soil, rather than a wooden deck that bounces with every step. Spread the tripod legs fully, tighten them, and use a level or simply your eye to get the mount roughly level. A level base makes tracking smoother and stops the tube from drifting.

Carry the telescope outside 30 to 60 minutes before you plan to observe. Glass and air inside the tube need time to match the outside temperature; until they do, warm air currents make stars look like wobbling blobs. Large reflectors, which use a mirror to collect light, can need an hour or more.

Align the finder in daylight

The finder is the small scope or red-dot sight on top of the main tube. It shows a wide area so you can aim, but it only helps if it points exactly where the telescope points. Do this in daylight: center a distant object, such as a treetop, chimney or mast at least half a mile away, in the main telescope with the low-power eyepiece.

Then adjust the finder's small screws until the same object sits on its crosshairs or red dot. Check again at night on a bright star and fine-tune. Never use the Sun for this step, not even briefly. Sunlight through a telescope or finder can blind you instantly and permanently, and it can also burn the eyepiece or crack a finder lens.

Eyepieces and focusing

Eyepieces are marked with a focal length in millimeters. The bigger the number, the lower the magnification and the wider the view. Always start with the longest one, often 25 mm or 32 mm. It makes finding things easy; you can switch to a higher power once the target is centered.

To focus, aim at the Moon or a bright star and turn the focus knob slowly in one direction. A star should shrink to the smallest, sharpest point you can get. If it grows into a fuzzy donut, you are going the wrong way. Each eyepiece needs a small refocus, and so may your partner if their eyesight differs from yours.

Your first targets

The Moon is the ideal first target: bright, large and impossible to miss. Look along the terminator, the line between day and night, where long shadows make craters and mountains stand out. A full Moon is very bright and flat-looking, so a few days before or after first or last quarter is better.

Next, find any bright planet that is up. Jupiter shows cloud belts and up to four moons, and Saturn shows its rings even at modest power. Then try the Pleiades, a star cluster in Taurus best seen from autumn to spring; use your lowest power, because it is wider than many telescope views. Our guide to seeing the planets helps you know what is up tonight.

Alt-az and equatorial mounts, simply

An alt-az mount moves up and down (altitude) and left and right (azimuth). It is intuitive: you just push or turn it toward the target. Because Earth rotates, objects drift out of view, so you nudge the scope every so often. At high power that drift is fast, which is another reason to start low.

An equatorial mount has one axis tilted to line up with Earth's axis. Once it is set, turning a single knob follows a star across the sky. Setting it is called polar alignment: in the Northern Hemisphere, you point that axis roughly at Polaris, the North Star, and set the tilt to your latitude. A rough alignment is plenty for looking; precise alignment matters mostly for photography.

Dark eyes, dew and collimation

Your eyes need about 20 to 30 minutes in darkness to reach full sensitivity, and one glance at a white phone screen undoes much of it. Use a dim red flashlight to read charts, and turn your phone's screen to night mode or red. Keep both eyes open while observing; it is more relaxed and steadier.

On clear nights, dew can form on the finder, eyepieces and the front lens of a refractor. A short dew shield helps, and a gentle hair dryer on low can clear it; never wipe wet optics. Dress warmer than you think, especially for your feet, since standing still is colder than walking. Reflectors also need occasional collimation, which means lining up the mirrors so they point at each other. It sounds technical, but it is a few screw adjustments, and a defocused star that looks like an off-center donut is the sign it is due.

Common mistakes and care

The most common mistake is too much magnification. Higher power makes the image dimmer, blurrier and shakier, and the Earth's air limits sharp views on most nights. Others are observing through a window, which ruins the view even when closed, setting up on a warm patio or rooftop that releases heat, and using a flimsy tripod that shakes at every touch. Our guide to magnification and eyepieces explains the limits.

After the session, cap the telescope only once any dew has dried indoors, so moisture is not trapped inside. Store it in a dry place, keep eyepieces in their case, and avoid touching or frequently cleaning lenses and mirrors; a little dust does far less harm than rubbing. Above all, keep the Sun out of the eyepiece at all times. Solar viewing needs a certified solar filter that covers the whole front of the telescope, meeting ISO 12312-2, and filters that screw into an eyepiece are unsafe.