Star Time-Lapse Settings: Calculating Frame Count, Interval, and Shooting Time

Decide the frame count from the video length

For social media or a single shot in a larger piece, around 10 seconds is a handy length. Allowing for trimming and speed changes in editing, it’s safest to shoot 10–20% more than you need. 24 fps gives a slightly stepped, cinematic motion; 30 fps looks smoother.

Chart of intervals and shooting times

The interval is the time from the start of one shot to the start of the next: exposure time + gap. Shooting 300 frames (10 seconds at 30 fps) takes the following time.

The longer the interval, the faster the stars move in the video. With a 15-second exposure and 20-second interval, 300 frames pack about 1 hour 40 minutes of sky motion (about 25° of rotation) into 10 seconds. Use a shorter interval to show stars drifting gently, and a longer one for dynamic clouds or a rising Milky Way.

How to decide the exposure per frame

A time-lapse ends up as 4K (3840×2160, about 8.3 megapixels) or Full HD (1920×1080, about 2 megapixels) video, so stars don’t need to be pinpoints as strictly as in stills. Turning a 24-megapixel photo (6000 pixels wide) into 4K shrinks it to about 1/1.56, and into Full HD to about 1/3.1, so star movement looks correspondingly smaller.

The table is for a 24-megapixel full-frame camera. For 4K video, even extending to simplified NPF (about 20 seconds at 14 mm) leaves stars looking almost like points. A longer exposure lets you lower the ISO, reducing noise and making flicker less noticeable. Shots you also want to use as stills should follow the NPF rule’s time. The differences between these rules are explained in NPF Rule vs. 500 Rule.

Estimating card capacity

RAW size is roughly proportional to pixel count, at about 1.1 bytes per pixel for 14-bit lossless compression. Here’s the capacity for 300 and 600 frames.

If you’ll shoot several clips in a night, bringing multiple cards of 64 GB or more is safest. You shoot RAW so you can even out brightness and color later. To make files smaller, some cameras offer lossless compressed RAW or smaller RAW sizes; if you’re exporting to 4K, reducing the pixel count makes almost no difference in quality.

Settings that prevent flicker and failure

• Lock shooting mode, ISO, F-number, shutter speed, and white balance all in manual
• Turn off long exposure noise reduction. If it’s on, each frame is followed by a wait as long as the exposure
• Turn off auto power off and image review so it doesn’t stop midway
• Batteries drain fast on cold nights, so use USB power or a high-capacity battery
• Prevent condensation with a lens heater. If the lens fogs partway, all later frames are unusable
• Keep the tripod low with its legs spread wide. Wind shake makes the whole video tremble
• Don’t shine a light on the scene during shooting, and watch out for headlights from other people’s cars too

The “holy grail” approach, spanning the big brightness change from dusk to night or night to morning, requires gradually changing the exposure and correcting flicker with dedicated apps or raw developers. To begin with, we recommend practicing fixed-exposure time-lapses, started once it’s fully dark.

1. 1

   Decide the video length and frame count

   10 seconds at 30 fps is 300 frames; allowing room for editing, aim for 330–360.

2. 2

   Decide the exposure and gap

   In the Astrophotography Calculator, check the seconds and suggested ISO in the “Max exposure without trails” tab, then enter exposure, gap, and frame count in the “Trails & time-lapse” tab.

3. 3

   Check the shooting time and capacity

   It shows the interval setting, shooting time, star rotation, and card capacity. Check that it won’t overlap moonrise or twilight and that your card has enough space.

4. 4

   Test shoot before starting

   Take about 10 frames and check that writing keeps up and that brightness and focus are right before starting for real. For focusing, see Focusing for Starscapes.

The frames you shoot can also become a still image of star trails through lighten compositing. For frame counts and intervals that keep trails unbroken, see How to Shoot Star Trails.

FAQ

How many frames do I need for a star time-lapse?

Video seconds × frame rate. 10 seconds at 30 fps is 300 frames, 20 seconds is 600, and 10 seconds at 24 fps is 240. Allowing for trimming in editing, it’s safest to shoot 10–20% more.

How many seconds should the time-lapse interval be?

For starry skies, “exposure time + about 2 seconds” is a good guide. For a 15-second exposure, use an interval of about 17 seconds, or 20 seconds on a camera with slow writing. A 15-second exposure and 20-second interval takes about 1 hour 40 minutes for 300 frames.

How long does a star time-lapse take to shoot?

Interval × (frames − 1) + exposure time. 300 frames at a 10-second exposure and 12-second interval takes about 1 hour; a 20-second exposure and 22-second interval takes about 1 hour 50 minutes.

Do I need to keep to the no-trail exposure limit for time-lapses?

It doesn’t need to be as strict as for stills. Turning a 24-megapixel photo into 4K video shrinks it to about 1/1.56, so at 14 mm F2.8, stars look almost like points even at simplified NPF’s roughly 20 seconds. Follow the NPF rule’s time only for shots you’ll also use as stills.

How many gigabytes of card do I need for a time-lapse?

A 24-megapixel RAW file is about 26 MB, so 300 frames is about 7.6 GB and 600 frames is about 15.2 GB. At 45 megapixels, 300 frames is about 14.6 GB. If you’ll shoot several clips in a night, prepare 64 GB or more.