Why can I not see anything through my telescope?

Almost everybody's first night with a telescope is frustrating, and it is nearly always one of a short list of causes rather than a fault. Working through them in daylight, at home, before an evening outside, solves most of it permanently.

Safety

What you'll need

• The low-power eyepiece
• A daylight target several hundred metres away
• The finder's adjustment screws
• A red torch

Step by step

1. Align the finder in daylight.This is the single most common reason people see nothing. Point the main tube at a distant fixed object — a chimney, a pylon, a church spire, never anything moving and never the Sun — centre it in the low-power eyepiece, then adjust the finder's screws until the same object is centred in the finder. Do it every session at the start; finders drift.
2. Always start with the lowest-power eyepiece.That is the one with the largest focal length in millimetres — a 25mm gives lower magnification than a 10mm. Low power means a wide field of view and a bright image, which is what you need to find anything at all. Increase magnification only after the object is centred.
3. Rack the focuser through its whole range slowly.Focus is often nowhere near where you expect. Turn the focuser slowly from one end of its travel to the other while looking through the eyepiece. A star goes from a large doughnut, through smaller rings, to a hard point. If you can never get a point, keep going — beginners frequently stop short.
4. Check the caps and covers.It sounds absurd and it happens constantly: the dust cap still on the front, the finder capped, or a secondary cover left in place. Look down the tube.
5. Let the telescope cool.A telescope brought outside from a warm house has air currents inside the tube and a warm mirror, producing an image that shimmers and will not focus. Half an hour outside for a small instrument and an hour or more for a large one. Store it in a shed or garage and it is ready immediately.
6. Reduce the magnification.British air is rarely steady enough for very high power. If the image boils, swims or is soft, put in a lower-power eyepiece — a smaller, sharper image shows more detail than a large blurred one. This is the opposite of what people expect and it is consistently true.
7. Check what you are trying to look at.Many beginners point at a random bright star and are disappointed that it is still a point of light — stars always are. Start with the Moon, which is unmistakeable and spectacular, then a bright planet. Use an app to confirm that what you are aiming at is actually a planet and is actually above the horizon.
8. Give your eyes time.Twenty minutes without looking at a white light, and a red torch thereafter. Faint objects are invisible to an eye that has just looked at a phone screen.
9. Check collimation on a reflector.Newtonian and Dobsonian mirrors go out of alignment with transport and use, giving soft images that never quite focus. A collimation cap or laser collimator makes it a five-minute job, and it is a normal part of owning a reflector rather than a fault.
10. Look at the sky honestly.Thin high cloud, haze, a bright Moon, streetlights and looking over a warm roof all destroy the view. Poor seeing is a real thing and no equipment fixes it. Some nights are simply not observing nights.
11. Clean optics rarely and carefully.Dust on a mirror has almost no effect on the image. Cleaning badly scratches coatings permanently. Leave it unless it is genuinely filthy, and then follow the manufacturer's method exactly.

Tips

• Practise everything in daylight on a distant object: finder alignment, focusing, changing eyepieces, and moving the mount. Doing it for the first time in the dark and the cold is why people give up.
• A dew shield and a hairdryer on a cool setting deal with dew, which fogs optics on clear British nights and ends sessions early.
• Keep a low-power eyepiece permanently in the telescope so the default state is the easy one.
• Note what you looked at and what the conditions were. It turns random frustration into visible progress.
• Local astronomical societies will happily look at your telescope and sort it out in ten minutes. Take it along.

Common mistakes

• Starting with the highest-power eyepiece — The field of view becomes tiny, the image dim, and finding anything nearly impossible. Low power first, always.
• Taking the telescope straight outside and expecting a sharp image — Warm optics produce currents inside the tube that no amount of focusing will fix. It needs time to reach air temperature.
• Using the small screw-in 'sun filter' supplied with some cheap telescopes — They sit at the eyepiece where the light is already concentrated, and they can crack under the heat. Solar viewing requires a full-aperture filter over the front of the tube, or nothing at all.

If it doesn't work

Questions people ask