I really appreciate a good sunset, and I want to be able to predict top-tier sunset opportunities based on aviation weather reports. I began a scientific study to determine exactly what factors create a jaw-dropping sunset.

Cloud Research using my drone

My science project was inspired by this photo I took on October 27th, 2020. I saw that the sunset was something special that day, and when I noticed this I took my drone out as quickly as I could, lifted off and tried to take a good picture of the sunset. But in the 2-3 minutes that it took to get set up and in position, half of the clouds had gone dark. Just a few minutes before this photo was taken, the sky was TWICE as bright with so much red you wouldn’t believe. And I missed the photo opportunity, the photo was not as good as it could have been if I knew what I was doing. And so, I started a study of clouds. Not just an internet research project, but a project involving taking photos myself and making note of all the variables that came into play that day. If I can perform perfectly and be prepared for a great sunset, I will be able to capture an insane sunset picture that I am proud of.

As a drone pilot, I can get a unique perspective of the sky, because the camera is in the sky. I can rise above trees and get an unobstructed view of a sunset. However, an amazing sunset does not happen every night. Some sunsets are much more aesthetic than others. One such factor is your location, and for me in my area, the best place to take a sunset photo would be anywhere that there is a body of water beneath, which would reflect the colors of the sky, doubling the amount of sunset colors in the photo. The sun paints orange and red and magenta in the sky, and to me the more non-blue and non-grey colors, the better the sunset.

If I were to rate sunsets on a scale of 1-10, a 10/10 sunset would be properly framed with an interesting foreground as well as a vibrant sunset. It would be taken at the correct time where the clouds are at their peak in terms of color. A 10/10 sunset would have the right amount of cloud coverage, not too much and not too little. The clouds will be at certain altitudes, because clouds that are too low are never lit up by the sun. These are the variables I seek to understand.

I need to predict a good sunset because I do not want to drive to the “perfect” sunset spot only to have a lame non-sunset, not get a good photo, and essentially waste time. So in this effort I have begun to be able to identify the different types of clouds. I am studying the timing of when clouds at certain altitudes become lit up by the sun. There is always an “official” sunset time for any location, so when is the optimal time to take the photo - 10 minutes before sunset? 10 minutes after?

In just a week of studying, I have already reached some conclusions. I will take it day-by-day and show each discovery from that day. All photos on this post are not edited for color in order to show what everything truely looked like when I did this study.

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01-17-2021

• Sunset time: 4:23 PM PDT (2021-01-18:0023 UTC)

METAR @ sunset time:

• KSZT 180035Z AUTO 24007KT 208V268 10SM SCT043 SCT049 01/00 A3028 RMK AO2
• KSZT 180015Z AUTO 25007KT 10SM OVC041 02/00 A3028 RMK AO2
• KSZT 172355Z AUTO 25007KT 10SM SCT021 OVC041 02/00 A3027 RMK AO2

The METAR weather report says that at 3:55pm there was a scattered cloud layer at 2100 feet amd an overcast cloud cieling at 4100 feet. The scattered clouds at 2100 cleared up by 4:15pm, and 12 minutes after sunset the overcast layer disappears and scattered clouds appear at 4300 and 4900 feet.

Cloud ID: Altocumulus. Time of photo: 4:16 pm (7 minutes before sunset)

This is an altocumulus cloud, which means it is mid-altutide (alto-), and is a fluffy cloud (cumulus). The is a southern-facing photo and from this photo you can see that only the western side of the cloud is lit up by the sun. The sunlight can’t penetrate the entire cloud, and so basically the cloud is too large to be fully illuminated. A better cloud formation would be smaller cumulus clouds spaced apart. Altocumulus floccus would be one of the best cloud formations to occur during a sunset. The cotton-candy cloud colors contrasting with the blue sky are very aesthetically pleasing.

Cloud ID: Stratocumulus humilus. Time of photo: 4:15 pm (6 minutes before sunset)

The cloud above the lake here is a stratocumulus humilus. It is low altitude (strato-), fluffy-ish cloud (cumulus) which is wider than it is tall (humilus). If it formed more of a layer, it would be a simple stratus cloud, but it has a well-defined fluffy form and is therefore stratocumulus. You can see that the higher altitude clouds (altocumulus) are lit up by the sun, while the lower altitude cloud does not catch the sun’s rays.

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01-18-2021

Sunset time: 4:25 PM PDT (2021-01-19:0025 UTC)

METAR @ sunset time:

• KSZT 190035Z AUTO 02003KT 10SM SCT036 OVC090 01/M02 A3046 RMK AO2
• KSZT 190015Z AUTO 00000KT 10SM BKN036 OVC090 01/M02 A3046 RMK AO2
• KSZT 182355Z AUTO 00000KT 10SM OVC036 02/M02 A3045 RMK AO2

The weather report says that at sunset time there is a broken cloud layer at 3600 feet, and an overcast cloud cieling at 9000 feet

Cloud ID: Altostratus. Time of photo: 4:36 PM (11 minutes after sunset)

This is an Altostratus cloud, with overcast cloud coverage.

Cloud ID: Altostratus. Time of photo: 4:41 PM (16 minutes after sunset)

This is the same Altostratus cloud, 5 minutes later. As you can see, timing was key. Clouds at this altitude peak at a very specific time. Low clouds like this will light up after sunset - after the sun is below the horizon - because the sun shines through the atmosphere at a tangent, and lights these clouds up from below. As light travels through the atmosphere, blue light is scattered, and red light remains and continues straight. This is why the air in sky is blue, and why clouds at sunset can be red.

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01-20-2021

Sunset time: 4:27 PM PDT (2021-01-21:0027 UTC)

METAR @ sunset time:

• KSZT 210055Z AUTO 00000KT 10SM CLR 01/M03 A3008 RMK AO2
• KSZT 210035Z AUTO 22003KT 10SM CLR 02/M03 A3008 RMK AO2
• KSZT 210015Z AUTO 20004KT 10SM CLR 02/M03 A3008 RMK AO2

The weather report says that at the time of sunset, the sky was clear. There are clearly scattered clouds in the photos. Maybe the weather station needs to be serviced. The accuracy of the weather station is certainly a part of this equation and makes sunset prediction that much harder.

Cloud ID: Stratocumulus, Altostratus, and Cirrocumulus. Time of photo: 2:13 pm (2 hours, 14 minutes before sunset)

These clouds are not aesthetically pleasing, but are important to be able to identify. There are a variety of clouds in this picture. Low on the horizon are a couple of stratocumulus clouds. In the middle is a sheet of altostratus translucidus clouds. Through the hole in that cloud sheet you can see high altitude, fluffy cirrocumulus clouds.

Cloud ID: Altostratus Time of photo: 4:11 pm (16 minutes before sunset)

Based on the sky from this day, I optimistically thought the sunset might be pretty good, based on my internet research about high-altitude clouds being a major key for a beautiful sunset. The high altitude clouds spaced apart seemed like they would be lit up all over the sky.

Cloud ID: Altostratus Time of photo: 4:12 pm (15 minutes before sunset)

These are the clouds which I thought might become red or orange. They were at the right altitude according to what I have read. I believe the clouds on the western horizon blocked the light from hitting the side of these clouds. If it were clear skies on the western horizon, these clouds would certainly have lit up.

Cloud ID: Time of photo: 4:40 pm (13 minutes after sunset)

Hilariously, this was the only cloud in the sky to be lit up around sunset time. The little, low cloud. Why? Possibly because of the altostratus layer was blocking the suns rays from above. The tops of them were most likely vibrantly lit, which we cannot see from below. When the sun was low enough, the light slipped under that cloud layer to light up the cumulus cloud below. Note that this cloud did not become lit at all until after sunset.

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01-23-2021

Sunset time: 4:32 PM PDT (2021-01-24:0032 UTC)

METAR @ sunset time:

• KSZT 240055Z AUTO 00000KT 10SM BKN031 M03/M07 A3004 RMK AO2
• KSZT 240035Z AUTO 00000KT 10SM CLR M03/M08 A3004 RMK AO2
• KSZT 240015Z AUTO 00000KT 10SM CLR M02/M08 A3004 RMK AO2
• KSZT 232355Z AUTO 00000KT 10SM SCT027 M02/M08 A3005 RMK AO2

Again the weather report says that at the time of sunset, the sky was clear - perhaps a malfunctioning weather station.

Cloud ID: Altostratus floccus. Time of photo: 4:13 pm (19 minutes before sunset)

These clouds, all over the sky, would make for a fantastic sunset.

Cloud ID: Altostratus radiatus. Time of photo: 4:25 pm (7 minutes before sunset)

These clouds were very interesting to me. Forming parrallel lines, this cloud formation is relatively rare. This is one of the more interesting clouds I have taken a picture of. I look forward to capturing more rare clouds like this with my drone.

Cloud ID: Altostratus translucidus. Time of photo: 4:41 pm (9 minutes after sunset)

This is the eastern horizon which was the part of the sky which was lit up the most around sunset time. The cloud coverage on the western horizon was too dense for any clouds to be visibly lit up.

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In conclusion

Learning to identfy clouds is essential for predicting a great sunset, in addition to reading and understanding the most recent local weather report. Knowing how each cloud behaves as the sun sets can help optimize your arrival time on location. If a certain type of cloud does not get lit until after sunset, it is not necessary to arrive early to get the picture you want. Dense clouds and extensive cloud coverage will not allow the light to illuminate the sky in the aesthetically pleasing way that we all know. My scientific research with my drone has confirmed what I have read online: you want mid-altitude clouds, with 30-70% cloud coverage. If it is completely overcast, you could comfortably skip any attempt at a sunset picture that day with no fear of missing out. I have found that sunsets are basically “over” about 15 minutes after official sunset time, and vibrant sunsets occur an-hour-before to 15-minutes-after offical sunset time. One of the most important aspects of sunsets is a partially clear sky, where the sun’s rays can travel and land on clouds, illuminating them. Too many clouds will simply block the suns rays, or light up the top of the cloud, which we cannot see from below.

I think the best advice would be: be in the right place at the right time, and simply capture the photo when the opportunity presents itself. It’s not really something you can force. As the clouds in the sky change rapidly, it can be very hard to predict if the clouds that are present 1 hour before sunset will still be around to give us the vibrant sunset we want. Keep your eye on the sky and your camera ready.

NO MORE MISSED OPPORTUNITIES!. This is 24 minutes after sunset, December 23, 2020. 15 minutes earlier, this photo would have been insane! I saw other peoples photos of the sunset from this day, and it was an incredible opportunity that I missed - these altocumulus undulatus clouds turned purple! It is helpful to know that I was too late with this photo, and not too early. If the photo wasn’t what I wanted and I chose to wait for the colors to improve, since I already missed the peak of the sunset I would be waiting in vain. It is at least good to know when it is time to call it quits. For future sunset photo opportunities, I will be checking the sunset 45 minutes prior to official sunset time, and flying from 20 minutes before to 15 minutes after since my drone batteries last 35 minutes. I should get an amazing sunset photo soon. Stay tuned.