π Blue Hour Calculator
Morning and evening blue hour windows for any date. Simplified solar math, not GPS precise.
Estimated twilight photography windows
Simplified estimate, typically within 5 to 15 minutes. Confirm critical shoots with a precise solar app.
How to Use This Calculator
Blue hour is brief, and missing it by ten minutes means missing it entirely. This calculator estimates the morning and evening blue hour windows for any date and latitude, so you can plan when to arrive, when to start shooting, and when the light is gone. Pick a preset city or enter your own latitude, choose a date, and the windows appear instantly.
Pick a Date. The blue hour shifts through the year as sunrise and sunset times move, so always calculate for the actual shooting day, not today.
Choose a City Preset or select Custom latitude and enter your decimal latitude. Southern hemisphere? Use a negative number, like -33.87 for Sydney.
Read the two windows: morning blue hour runs before sunrise, evening blue hour after sunset. The calculator also shows sunrise and sunset themselves as anchors.
Plan to arrive 20 minutes before the window opens. Scouting the composition in daylight and setting up the tripod early is the difference between shooting and scrambling.
The Formula: Simplified Sunrise and Sunset
The calculation starts with the day of year to find the sun's declination, the tilt-driven angle that makes days long in summer and short in winter. Combined with your latitude, the hour angle formula gives the moment the sun's center crosses 0.83 degrees below the geometric horizon, the standard definition of sunrise and sunset that accounts for atmospheric refraction. Solar noon is approximated at 12:00 local time, which ignores your longitude within the time zone and the equation of time: that is the main source of the 5 to 15 minute error.
Blue hour itself is defined by solar elevation between about 4 and 8 degrees below the horizon. Rather than solving for those exact elevations, the calculator applies the field-tested approximation: the rich blue phase runs roughly 20 to 40 minutes before sunrise and 20 to 40 minutes after sunset, with the sweetest color usually in the middle of that band. At higher latitudes the sun's path is shallower, so the real window stretches; the calculator widens the band with latitude to reflect that.
Worked Example
New York, October 15 (day 288 of the year), latitude 40.71. Declination = -23.44 x cos(360/365 x 298) = about -8.0 degrees. The hour angle works out to roughly 96 degrees, giving sunrise near 7:05 AM and sunset near 6:15 PM local solar time. Morning blue hour: about 6:25 to 6:45 AM. Evening blue hour: about 6:35 to 6:55 PM.
Notice how tight that is: 20 minutes of prime blue each way. In mid-June the same city gets longer evenings and a slightly wider window; in December the morning window lands near 6:40 AM but the sun barely climbs, so twilight colors linger. That seasonal swing is exactly why you calculate per date instead of memorizing times.
Practical Tips
Shoot the evening window first if you are new to blue hour. You can scout in daylight, watch the sunset, and keep shooting as the sky turns blue, with no alarm clock involved. The morning window is equally beautiful and far less crowded, but it demands arriving in the dark with everything pre-planned.
Manage the exposure ramp. Light fades fast during blue hour, sometimes a full stop every few minutes. Check the histogram every few frames and lengthen the shutter to compensate. Auto ISO with a minimum shutter speed can help, but for cityscapes on a tripod, manual mode with a lengthening shutter keeps the aperture and depth of field constant while the sky does its thing.
Frequently Asked Questions
What is the blue hour in photography?
The blue hour is the twilight period when the sun is 4 to 8 degrees below the horizon and the sky glows deep blue. It happens roughly 20 to 40 minutes before sunrise and after sunset. City lights, windows, and street lamps balance beautifully against the blue sky, which is why cityscapes shot then look magical.
How long does the blue hour last?
Typically 20 to 40 minutes, but it varies with latitude and season. Near the equator it is short, around 20 minutes. At higher latitudes in winter it can stretch past 40 minutes because the sun descends at a shallower angle. This calculator estimates the window from your latitude and date.
Is blue hour the same as golden hour?
No. Golden hour is when the sun is above the horizon (0 to 6 degrees up) and the light is warm and low. Blue hour comes after sunset and before sunrise, when the sun is below the horizon and the light is cool blue. They often happen back to back: shoot golden hour, keep shooting through sunset, and you roll straight into blue hour.
How accurate is this simplified calculator?
It uses a day-of-year solar model that is typically within 5 to 15 minutes of the true times. It does not account for your exact longitude within the time zone, elevation, mountains, or daylight saving quirks at borders. For casual planning it is plenty; for a once-in-a-trip shot, arrive 30 minutes early and confirm with a precise app.
What camera settings work best during blue hour?
Use a tripod: exposures run 1 to 30 seconds as the light fades. Start around ISO 100 to 400, aperture f/8 to f/11 for cityscapes, and let the shutter do the work. Shoot RAW and bracket exposures, because the sky darkens fast and the best balance of sky to city lights lasts only a few minutes.
Can I shoot blue hour portraits?
Yes, and they look stunning: the blue sky acts as a giant softbox while warm city lights add rim light. You will need a flash, LED panel, or a cooperative street lamp on your subject, since ambient light is too dim for faces. Expose for the sky, then add just enough light on the person to match.