Answer a few questions about your camera and we'll tell you what settings to start with tonight — using the live Kp index and current moon brightness. No photography jargon required.
Not sure about a number? Megapixels and sensor size are on your camera's spec sheet or box. Aperture (f-number) and focal length (mm) are printed right on the lens.
Open your aperture as wide as it goes (lowest f-number), then let the calculator's shutter speed and ISO guide your starting point. Take a test shot, look at it, and adjust — this tool gets you in the right neighborhood, not a perfect answer on the first try.
Brighter, faster-moving aurora (higher Kp) wants a shorter shutter speed so the pillars and curtains don't blur into a green smear. Fainter, calmer aurora wants a longer shutter speed to gather more light. A bright moon lets you use a lower ISO, but it also washes out faint aurora — that's a real tradeoff, not something to avoid.
Sensor size + megapixels determine how tightly packed your camera's pixels are, which affects how long you can leave the shutter open before stars start to blur into short streaks instead of points. We calculate this instead of asking you to look up "pixel pitch" — a spec most people have never heard of.
Focal length and aperture come straight off your lens. A wider lens (smaller mm number) tolerates a longer shutter speed before star trails show up; a wider aperture (smaller f-number) lets in more light so you need less ISO or a shorter shutter.
Max ISO is just "how much grain are you willing to accept" — there's no wrong answer, it's a personal preference based on your camera and how the photo will be used.
The shutter speed cap comes from the NPF rule: max seconds ≈ (35 × aperture + 30 × pixel pitch) ÷ focal length. It's more accurate than the older "500 rule" because it accounts for your sensor's actual resolution — a 61-megapixel camera shows star trails much sooner than a 12-megapixel one at the same settings, since its pixels are smaller and more sensitive to the tiniest bit of motion.
Want the reasoning behind these numbers, a gear list to get started, or a sense of what the night actually involves? See Camera Settings Explained, the gear guide, and what to expect.