It's time to return to the routine in which every "Sky Lapse" blog post includes a panoramic composite image followed by a panoramic time lapse video.
The panoramic composite image was taken using the "Camera" app on my Apple iPad mini 6, set for "Pano" mode. The image shows a wide view along the horizon.
17 December 2025. Facing north. (15298 x 3633 pixels)
A little later during the same afternoon a panoramic time lapse video was taken using my GoPro HERO4 Black action camera set for "Video" mode / "Time Lapse Video" submode at a resolution of 4K and an interval of two (2) seconds. The camera was mounted in a fixed position, facing north-northwest in the first clip and facing south-southwest in the second clip.
17 December 2025
Related Resources
Altostratus (As) | International Cloud Atlas - World Meteorological Organization
The word "subsensory" means 'below the threshold of sensory perception.' Time lapse video recorded at 30 frames-per-second can contain sub-sensory imagery, such as the following examples from a recent time lapse of altostratus clouds captured on 17 December 2025 using my GoPro HERO4 Black action camera.
As you watch the video, can you see more than six jet airplanes that flew past the Sun? Probably not, but they're there! They're sub-sensory. I saw the airplanes when I used the left/right arrow keys to go back-and-forth through the video frame-by-frame; every plane is visible for several frames.
17 December 2025. Facing south-southwest.
Reagan National (DCA) is the airport nearest my home. My location is near the flight path of air traffic approaching and departing the airport, depending upon the wind direction. I saw more than six jet airplanes during the time I recorded the preceding time lapse video.
17 December 2025 | Elapsed time: 00:14
06. Jet airplane partially eclipses the Sun.
17 December 2025 | Elapsed time: 00:00 (less than 1 s)
01. Jet airplane plus large bird (lower-right corner).
I like the juxtaposition of a man-made bird and a natural bird in the preceding image. I saw the bird flying around in loops as the jet airplane moved from left-to-right across the sky. My good friend Mike Boatwright is a bird expert. Mike thinks the bird might be a Turkey Vulture.
Looks like a Turkey Vulture. They hold their wings uplifted like that and fly around in circles. Source Credit: Personal communication, Mike Boatwright.
17 December 2025 | Elapsed time: 00:02
02.
17 December 2025 | Elapsed time: 00:04
03.
17 December 2025 | Elapsed time: 00:08
04.
17 December 2025 | Elapsed time: 00:12
05.
The Backstory
The following iMovie features the first time lapse videos (two) I captured using my GoPro HERO4 Black action camera. The camera was set for "Video" mode / “Time Lapse Video” submode, using a resolution of 4K and an interval of one (1) second. The first video clip (00:28 s) is longer than the second clip (00:17).
27 April 2022. Facing east.
Notice the clouds are moving slowly from left-to-right across the screen; the jet airplanes are flying from right-to-left across the screen, since planes prefer to take off and land flying into the wind. Oh that's right -- you probably can't see the planes. Neither could I.
Post update: I watched the time lapse movie on a large screen monitor. Although I saw several planes in the sky (with my eyes) when I was outside, I don’t see them in the movie. That’s odd, because the camera was set to record every 1 s — more than long enough for a single plane to appear multiple times. Source Credit: GoPro Time Lapse Video: Richmond Highway (U.S. Route 1) - a blog post by Walter Sanford.
I saw the following sub-sensory images when I used the left/right arrow keys to go back-and-forth through the videos frame-by-frame.
In the shorter video segment, I saw a bird at 00:07, 00:10, and 00:11 seconds of elapsed time. A jet airplane is visible for several frames from 00:12 - 00:13 seconds of elapsed time. The images of the plane look hazy due to humidity in the air. Disclaimer: The elapsed times are for the original video clips. The equivalent times in my iMovie are different due to the addition of titles, transitions, etc.
27 April 2022 | Elapsed time: 00:12 - 00:13
01. Screenshot of a jet airplane.
27 April 2022 | Elapsed time: 00:12 - 00:13
02. Another screenshot of a jet airplane.
A large bird can be seen near the end of the longer video segment. Disclaimer: The elapsed time is for the original longer video clip. The equivalent time in my iMovie is different due to the addition of titles, transitions, etc.
Altostratus (As) clouds were observed in the sky over Fairfax County, Virginia USA during the afternoon of 17 December 2025. Notice the Sun looks like it's shining through frosted glass.
The following photo was taken using the built-in "Camera" app on my Apple iPad mini 6.
Altostratus clouds (As). Facing south-southwest.
A time lapse video was taken using my GoPro HERO4 Black action camera. The camera was set for "Video" mode / "Time Lapse Video" submode, using a resolution of 4K and an interval of two (2) seconds. The camera was mounted in a fixed position, facing south-southwest.
Related Resources
Altostratus (As) | International Cloud Atlas - World Meteorological Organization
The following time lapse videos were created using "Skyflow," an iOS app running on my Apple iPad mini 6. Both videos show the sky over Fairfax County, Virginia USA during the afternoon of 17 December 2025.
I'm still not sure where to focus for maximum depth of field. (Please comment on this blog post if you can offer advice.) In the first video, I think I focused on the top of the red roof. I say "think" because it's difficult to see the screen of my iPad clearly when I'm outdoors.
Facing south-southwest.
In the second video I think I focused on the light blue water tower along the horizon, just left of the center of the screen.
Facing north-northwest.
Notice the wave-like shapes in the clouds, moving from left-to-right across the screen. I'm not sure what caused those features to form but they might be the result of small waves moving through the atmosphere.
Both video clips were combined using Apple iMovie.
What are the take-aways from my first field test?
Skyflow is a robust app that provides the user with much more control over the process of creating time lapse videos than the built-in Apple iOS "Camera" app set for "Time-Lapse" mode.
There is a learning curve to reach mastery of the app. I learned enough to be able to take a couple of test time lapses but feel like I'm just a beginner, despite being a fairly experienced photographer.
The descriptor for Skyflow in the Apple App Store provides a long list of what the app can do but doesn't say how those features work. There is some embedded documentation (see Settings/Help); I skimmed that information and still have unanswered questions. The author personally assured me he's planning to create a tutorial video that explains how the app works. In the meantime, I recommend watching the videos listed under "Related Resources."
My initial impressions of Skyflow are very positive. I'm eagerly looking forward to feeling more comfortable using its many features.
Tech Tips
The first two videos were adjusted using the built-in editor to level the horizon. The first video was also cropped slightly for better composition.
Essentially the first two videos are shown "as is," exported straight from the Skyflow app using the following settings: 4K (2160p); 30 fps; H.264 (MP4); Best Quality; and Smooth Motion.
Related Resources
Skyflow - Apple iOS app for creating time lapse videos, by Andrei Kovalev
Does the GoPro HERO4 Black action camera autofocus? No, the GoPro HERO4 Black action camera has a fixed focus lens with an aperture of f/2.8. The camera is configured so that it's focused at the "hyperfocal distance."
The concept of hyperfocal distance is easy to understand: focus a lens at the hyperfocal distance and everything in the photograph from some near distance to infinity will be sharp. Landscape photographs are often taken with the lens focused at the hyperfocal distance; near and distant objects are sharp in the photos. Source Credit: Hyperfocal Distance Guide, by Don Fleming.
The following video is a proof of concept example of hyperfocal distance in action. The black rock in the middle of the creek is approximately five feet (~5′) from the place in the stream channel where I was sitting on a Coleman camp stool. The video begins with me looking at a seep that feeds the stream; then I pan left, right, and back to center stage. Notice everything in the video is acceptably in focus because the camera is always focused at the hyperfocal distance.
Here is a collection of more factoids about the GoPro Hero4 Black action camera that might help you to understand how the camera works.
"The GoPro Hero4 Black has a 1/2.3-inch CMOS sensor with physical dimensions of 6.17 mm x 4.55 mm. This sensor has 12 megapixels and is capable of recording video at up to 4K resolution."
As you can see, the GoPro HERO4 Black action camera sensor is small, very small!
The 35mm equivalent focal length of the lens is ~15mm. That's a fairly wide angle lens, so photos show some "fish eye" distortion.
When the GoPro HERO4 Black is set for "Time Lapse Video" submode, the camera records MP4 videos with a 16:9 aspect ration (3,840 x 2,160 pixels). File size varies depending upon the duration of the video clips.
The GoPro HERO4 Black records JPG photos with a 4:3 aspect ration (4,000 x 3,000 pixels). Each photo file is ~2.2 MB in size.
"The GoPro Standard Housing is a spare/replacement housing for your GoPro HERO3, HERO3+, or HERO4 camera. A flat glass lens affords maximum image clarity above and below water. Plus, it's waterproof down to a depth of 131', and it features large buttons for easy camera control -- even when wearing gloves or mittens. The housing includes Standard, Skeleton, and Touch Backdoors plus a thumbscrew and Quick Release Buckle." Source Credit: B&H Photo.
The Motions of the Sun Simulator can be used to explore the apparent motion of the Sun across the sky on the December Solstice. The following screenshot shows the simulator configured for 21 December at 12 noon. Be sure to set the "animation mode" for "continuous" and "loop day," as shown in the red rectangle on the graphic.
"Motions of the Sun Simulator" set for DEC 21.
Notice the Sun rises along the southeastern horizon and sets along the southwestern horizon. At Washington, D.C. (38.89° North latitude and 77.03° degrees West longitude) the Sun reaches a maximum altitude of ~28° above the horizon, the lowest maximum altitude all year.
Also notice the odd-looking figure eight that is shown in red on the preceding screenshot. It's called an analemma. The crest of the figure eight shows the Sun's maximum altitude on the June Solstice.
The following panoramic time lapse video was taken during the afternoon of 04 December 2025, soon after shooting the pair of panoramic composite images featured in my last blog post.
04 December 2025. Panoramic view.
The sky was filled with a variety of higher cirroform and lower stratiform clouds, moving from southwest to northeast across the sky.
Tech Tips
The precedinging panoramic time lapse video was taken using my GoPro HERO4 Black action camera mounted on a "360TL" rotating timer. The camera was set for "Video" mode / "Time Lapse Video" submode, using a resolution of 4K and an interval of two (2) seconds.
Related Resource
Halo - a blog post by Walter Sanford (hey, that's me!), featuring panoramic composite images of the sky from the same day as the panoramic time lapse video shown above.
