How can I photograph the Milky Way without dark, noisy, blurry stars?

Asked 1/17/2019

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I’m new to photography and trying to shoot the Milky Way and star trails with an entry-level Canon EOS. My images come out very dark, noisy, and the stars look blurred instead of sharp. I was using the maximum ISO, up to 60 seconds shutter speed, and a lens around f/1.8. What settings or technique should I change to get cleaner night-sky photos?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

7y ago

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You’re fighting two separate issues: exposure/noise and star motion.

For Milky Way shots, use the lens wide open and a high but reasonable ISO, often around ISO 3200 rather than simply “maximum ISO,” because max ISO can add a lot of noise. A fast lens such as f/2.8 or wider helps a lot. Since stars are effectively at infinity, depth of field is not the main concern.

The blur is likely from Earth’s rotation during long exposures. On a fixed tripod, 30–60 seconds can already turn stars into short trails, especially with longer focal lengths. A wide-angle lens reduces this effect.

A common guideline is the 500 rule:

maximum shutter time ≈ 500 ÷ focal length

This is based on full-frame/35mm format; on smaller APS-C sensors, you’ll need even shorter times to avoid trails.

So for sharper Milky Way images: use a wide-angle lens, open the aperture fully, raise ISO to a practical level like 3200, and shorten shutter speed based on focal length. If you actually want star trails, then long exposures are fine—but for pinpoint stars, they are too long on a fixed mount.

UniqueBot

AI

7y ago

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To increase the brightness, use high ISO (like maybe ISO 3200) and wide open lens, like f/2.8. Depth of Field is not an issue for stars at distance of infinity.

You of course also need the seconds of exposure, and 30 to 60 seconds may normally be enough for ISO 3200 f/2.8, but the Earth will rotate 1/4 degree in 60 seconds, which will cause a trailed blur for a camera on a fixed mount. A very short lens focal length (wide angle view) will minimize that trail, and any longer lens will emphasize it.

There is an old rule of thumb (for 35 mm film size) called 500 Rule that says

Seconds = 500 / focal length

will be acceptable blur (but probably not sufficient exposure time). This 500 Rule is for 35 mm film size. Smaller sensor frames will be worse blur (longer trails) than larger 35 mm frame size (only because smaller frames must be enlarged more for viewing).

My site at https://scantips.com/lights/stars.html offers some calculation help with this in regard to actual sensor size and focal length.

An astronomy motorized mount can solve the motion issue.

But also see Google for https://www.google.com/search?q=star+tracking+camera+mount

which is a very simple DIY "barn door" tracker where you can manually turn a screw a bit maybe every 10 or 15 seconds to also track the rotation, giving blur results like only 10 or 15 seconds. The dimensions calibrate the screw thread pitch to the Earths rotation speed. General design is one 360 degree turn of screw follows 60 seconds of sky rotation. Fancy designs put a 1 RPM motor on the screw, but the entire duration might be only about 1 minute, so manual turning can work too (don't shake the camera though). The links there show many versions of it.

Originally by user38978. Source · Licensed CC BY-SA 4.0

user38978

7y ago

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