If the Moon looks huge tonight, you are almost certainly looking at it low in the sky, next to houses, trees, hills, or a skyline. That reported appearance is real. It is also a different thing from the physical size of the Moon or its width in a photograph.
The fast checklist
- Is it near the horizon?
- Then you are seeing the horizon effect. How strong it looks varies from person to person and with how detailed the scene is.
- Is it being called a supermoon?
- Then it may be a little closer than average. That is a real change in apparent size, and a separate one from the horizon effect.
- Is it orange or red?
- That colour comes from looking through more atmosphere. Colour, sharpness, and a slight vertical squash are atmospheric. The huge look is not.
- Does it look tiny on your phone?
- A wide phone lens gives a half-degree Moon a small part of the frame. The phone is not shrinking it.
Could it really be closer?
Yes, a little. The Moon travels in an ellipse rather than a perfect circle, so its distance from Earth changes and so does its real apparent diameter. Across the comparison NASA uses, the closest full Moon of the year can appear up to about 14 percent larger in diameter than the farthest. That is the extreme across a whole year, not a change between moonrise and midnight.
For scale: the Moon is about 3,475 kilometres across and, on average, about 384,400 kilometres away. Both are averages, not the exact figures for tonight.
Why does my phone make it look tiny?
The full Moon spans roughly half a degree of sky. A wide-field phone image gives only a small part of its frame to that disc unless optical magnification or cropping narrows the composition. A longer lens narrows the frame. It does not make the Moon bigger. Field of view and processing vary by device.
What should I do with this information?
Enjoy it. Then, if you like, curl your hand into a tube and look at the Moon through it so the scenery disappears. For some people that changes how big it looks. It does not tell anyone why. The field test on the main page has two more things to try.