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 Resource
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.
A halo around the Sun or Moon means precipitation in 12-24 hours, according to weather folklore. Turns out the prediction was correct as light snow fell the next day.
04 December 2025. Halo around the Sun. (15540 x 3832 pixels)
Another panoramic composite image was taken facing in the opposite direction.
04 December 2025. Facing north. (14468 x 3376 pixels)
The next two photos were "misfires" when I started a "Pano" shot accidentally. Twice. The weather was cold and windy -- my fingers were frozen! (That's my excuse and I'm sticking to it.) I kept the photos because they show cirrocumulus clouds (Cc) especially well.
04 December 2025.
04 December 2025.
Tech Tips
The preceding panoramic composite images were taken using the "Camera" app on my Apple iPad mini 6, set for "Pano" mode. Both images show a wide view along the horizon.
Here's how to capture very wide views of the sky. Start recording and rotate the iPad camera slowly and steadily on a tripod -- the slower you rotate the camera, the wider your "Pano" will be. Keep rotating the camera until the white arrow (on-screen guide) goes as far as it can -- at that point the recording will stop automatically.
I suggest you record a wider view than you need/want. For better composition, you can crop the image to remove distracting elements from the left and right sides of the composite image.
Related Resources
Halo Phenomena | International Cloud Atlas - World Meteorological Organization
The following panoramic time lapse video was taken just before sunset 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.
Two motions -- the rotation of the Earth around its axis, and the revolution of the Earth around the Sun -- cause daily- and annual cycles in the Sun's apparent path across the sky. Every day, the Sun appears to move across the sky from east to west as the Earth rotates counterclockwise. And from day-to-day, the apparent path of the Sun across the sky changes slowly due to the tilt of the Earth's axis and the Earth's revolution around the Sun.
The Motions of the Sun Simulator can be used for open-ended exploration of daily and annual motions of the Sun. The following screenshot shows the simulator configured for 22 November at 12 noon. Notice the Sun rises along the southeastern horizon and sets along the southwestern horizon.
Motions of the Sun Simulator. 22 November.
Related Resources
A pair of panos - a blog post by Walter Sanford, featuring panoramic composite images of the sky from the same day as the sunset panoramic time lapse video shown above
