Theodolite

Theodolite is an award-winning app for Apple iOS that has many applications for my sky watching activities. Wait, what is a "theodolite?"

A surveyor's instrument for measuring horizontal and usually also vertical angles. Source credit: Merriam-Webster (dictionary).

Tracking cloud motion

I used the "Theodolite" app to determine the position of the four cardinal points for my location. That enables me to know the direction clouds are moving across the sky.

15 JUN 2026 | Facing north.

15 JUN 2026 | Facing east.

15 JUN 2026 | Facing south.

OK, I was a little off-center for the direction "south."

15 JUN 2026 | Facing west.

Tracking weather satellites

Radio signals from polar orbiting weather satellites can be received using free software and relatively inexpensive hardware including an RTL-SDR and V-dipole antenna. For best results the V-dipole antenna should be oriented north-south, with the open end of the "V" facing south. For more information, see the following article: Simple NOAA/Meteor Weather Satellite Antenna: A 137 MHz V-Dipole.

Oh by the way, of course I used the "Theodolite" app to determine the direction of north and south relative to the position of my portable rig for reception of weather satellite radio signals.

Tracking daily- and annual cycles in the Sun's apparent path across the sky

The June Solstice will occur at 8:25 UTC on 21 June 2026 (4:25 a.m. EDT), according to the Earth's Seasons - Equinoxes, Solstices, Perihelion, and Aphelion page, Astronomical Applications Department, U.S. Naval Observatory.

The Motions of the Sun Simulator can be used to explore the apparent motion of the Sun across the sky on the June Solstice. The following screenshot shows the simulator configured for 21 June at 12 noon. Be sure to set the "animation mode" for "continuous" and "loop day," as shown in the following graphic.

"Motions of the Sun Simulator" set for 21 JUN at 38.8 N latitude.

Notice the Sun rises along the northeastern horizon and sets along the northwestern horizon. At Washington, D.C. (38.89° North latitude and 77.03° degrees West longitude) the Sun reaches a maximum altitude of 74.7° above the horizon, the highest maximum altitude all year. "This maximum angle occurs precisely at local solar noon, which usually happens around 1:00 PM EDT due to the Earth's axial tilt of 23.5° and daylight saving time adjustments." Source Credit: Google AI.

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 northern latitude on the June Solstice.

Many years ago I used the "Theodolite" app to show the direction of sunrise on the March Equinox. You might want to do something similar for either sunrise or sunset on the June Solstice.

20 MAR 2011 | 7:12 a.m. | Facing east.

Tech Tips

The following settings were selected under "PREFS" (upper-left corner) / "Camera Options...": "Screenshot"; "Photo Size" <100%>; and "Also Save Regular Image" <Yes>. 

The "Theodolite" app isn't available for devices running the Android OS. According to Google AI, the top-rated comparable app is "Sololocator - GPS Field Camera" ($0.99), available from Google Play.

Related Resources

• Theodolite Augmented Reality Navigation Viewfinder for iPhone and iPad
• Theodolite / Theodolite HD User Manual
• Earth's Seasons - Equinoxes, Solstices, Perihelion, and Aphelion - Astronomical Applications Department, U.S. Naval Observatory
• Motions of the Sun Simulator - University of Nebraska-Lincoln Department of Physics and Astronomy
• Position of the Sun on the horizon at sunrise - University of Nebraska-Lincoln
• Equinox sunrise - walter sanford's photoblog
• Sunrise Positions in Washington, D.C. - a post from my old Web server, rescued from the Wayback Machine Internet Archive, featuring a time series of photos by Dr. Robert Weinbeck, American Meteorological Society

Copyright © 2026 by Walter Sanford. All rights reserved.

Field testing the Viltrox DC-A1 camera monitor

The following YouTube video includes three time lapse video clips that show the sky over Fairfax County, Virginia USA during the afternoon on 09 June 2026. Three photo sets were captured using a Fujifilm X-T3, 18-55mm kit lens, and Viltrox DC-A1 camera monitor. Each photo set was rendered to video using Apple "QuickTime Player"; each movie clip was edited using Apple "Photos." The final video was created using DaVinci Resolve.

09 June 2026 | Fairfax County, Virginia USA

The sky was overcast to mostly cloudy, covered by high level cirroform clouds at 25,000 feet. Notice the cirrocumulus clouds visible in all three video clips.

Source Credit: KDCA | National Weather Service.

Tech Tips

A "Viltrox DC-A1 2800 Nits 7-Inch Camera Monitor" enabled me to see the camera display clearly, even in direct afternoon sunlight. The monitor sells for $278.00 MSRP; I bought it on sale for $236.30 from B&H Photo. The DC-A1 comes with a snap-on/off Sun Hood, L-series/NP-F550 battery, HDMI Type-A cable, HDMI Type-A to Mini-HDMI cable, and USB-C power cable (USB-C to USB-A), among other accessories.

My Fujifilm X-T3 connects to the Viltrox DC-A1 via a micro-HDMI to full-size HDMI cable, not included with the monitor. (My Fujifilm X-T1 features a mini-HDMI connector, but HDMI Output works only during Playback.)

The Viltrox DC-A1 can be used to show the display of my Apple iPad mini 6 by connecting the iPad to a CalDigit SOHO Dock via a USB-C cable, then connecting the SOHO to the Viltrox DC-A1 via a full-size HDMI cable. Although the display size of the Apple iPad mini and Viltrox DC-A1 is similar, the DC-A1 is much brighter than the iPad (as shown below).

It's all about "nits."

"nits" is a quantitative measure of screen brightness. The following bulleted list shows the brightness (in nits) for many of the cameras and devices I own.

• Viltrox DC-A1 Camera Monitor = 2800 nits
• Apple iPad mini 6 = 500 nits
• Samsung Galaxy Tab A9+ = 480 nits
• Fujifilm X-T3 = estimated 300-400 nits
• Fujifilm X-T1 = no official rating (seems to be dimmer than X-T3)
• Panasonic DMC-FZ300 = estimated 400-500 nits
• Canon EOS 5D Mark II = estimated 350-400 nits
• GoPro HERO4 Black action camera = There is no viewfinder screen on the back of the HERO4 Black, only a small "Camera Status Screen" on the front of the camera. (GoPro "Quik" app runs on Apple iPad mini 6, therefore 500 nits.)
• Skyflow (iOS app) = Runs on Apple iPad mini 6, therefore 500 nits.

In contrast with the Viltrox DC-A1, the highly rated Atomos Ninja 5.2" 4K HDMI Recording Monitor has a smaller screen, isn't as bright (1,000 nits), and sells for a higher price ($589.00 MSRP). Yes, the Atomos can record video, but so can my cameras.

Related Resources: Blog posts with label "Fujifilm X-T3" and "Fujifilm X-T1."

Copyright © 2026 by Walter Sanford. All rights reserved.

More Fisheye on the Sky

The following YouTube video -- including two "all sky" time lapse videos and a panoramic composite image -- shows the sky over Fairfax County, Virginia USA during the afternoon of 01 June 2026. A Fujifilm X-T1 plus Meike 6.5mm circular fisheye lens was used to capture the two "all sky" time lapse video clips. The panoramic composite image was captured using the "Camera" app on an iPad mini 6, set for "Pano" mode.

The entire dome of the sky is shown in the 190° circular field of view in the "all sky" time lapse videos: the zenith is located in the center of circle; the horizon is located around the outer rim of the circle. The sky was covered by low level cumuliform clouds and high level cirroform clouds. Notice the wind shear between the lower- and upper level clouds: the cumiliform clouds are streaming from north to south; the cirroform clouds are streaming from west to east.

01 June 2016 | Fairfax County, Virginia USA

The tree on the left side of the panoramic composite image is the same one shown in the second time lapse video clip.

Tech Tips

DaVinci Resolve was used to create the YouTube video. Not bad for my second video created using DaVinci, if I do say so myself.

Two short video clips and one composite panoramic image were used to create the movie. In order to avoid losing frames of content, "jump cuts" were used between the three media segments. Simple "fade out/in" transitions (one second) were used for the title- and credits screens, respectively. 

Related Resources

• Field testing an X-T1 for time lapsing - after action report - a blog post by Walter Sanford
• More quick-and-dirty video editing using QuickTime Player - another blog post by Walter Sanford
• DaVinci Resolve Instruction Manual (PDF)

Copyright © 2026 by Walter Sanford. All rights reserved.

Field testing an X-T1 for time lapsing - after action report

I own three Fujifilm X Series cameras (featuring an APS-C sensor): an X-T1; X-T3; and X-T5. The camera body is slightly bigger and heavier from the X-T1 to the X-T3 to the X-T5. To some extent that's a moot point when the camera is used for time lapsing, since it is mounted on a tripod. But it's worth noting because for me part of the appeal of the X-T1 was it's smaller and lighter than my Canon 5D Mark II full-frame sensor camera.

The X-T1 = 16.3 MP (number of effective pixels). The X-T3 = 26.1 MP. And the X-T5 = 40.2 MP. In some ways, the X-T3 is the Goldilocks of my Fujifilm cameras -- it takes photos that are neither too small nor too big -- they're just the right size for time lapsing.

Why try the X-T1 for time lapsing?

So why did I decide to field test the X-T1 for creating time lapses? Because I would rather not have to change lenses every time I want to shoot either an "all sky" time lapse or "wide angle" time lapse. You might be asking yourself "Isn't interchangeable lenses one of the more compelling reasons to buy a better camera?" Yes, it is. But every time you remove a lens from the camera body is an opportunity for dust to settle on the camera sensor. And that's not good. So I prefer to change lenses only when necessary, under controlled conditions.

My tentative plan was to be able to use my X-T1 with the Meike 6.5mm circular fisheye lens for "all sky" time lapses and use my X-T3 with the 18-55mm kit lens for "wide angle" time lapses. My plan probably would work if I set the X-T1 to shoot JPEG only, but I prefer to shoot both JPEG plus RAW images. Although I don't always use the RAW files, I like to have them in case I need them.

Strike 1. The write speed is too slow!

In the end, the slower write speed of the X-T1 processor doomed my plan. A five (5) second interval is probably sufficient time for the camera to save both JPEG and RAW files to a memory card. In my experience a five (5) second interval for "sky lapses" makes time seem to pass too quickly, so that's a no go.

I prefer using a two (2) second interval for "sky lapses." I set the X-T1 for a three (3) second interval as a compromise to enable the camera to write files to the memory card. But it was immediately evident the X-T1 struggled to write files that quickly. (It's worth noting the X-T3 can save compressed RAW files (RAW RECORDING > COMPRESSED); the X-T1 cannot.)

Strike 2. The X-T1 LCD is too difficult to see outside!

The X-T1 LCD screen doesn't have an official rating for brightness (in nits) but it might be the dimmest screen of all the cameras I own. I had to remove the camera from the tripod and go to a shady place in order to test exposure and make the settings for "INTERVAL TIMER SHOOTING" and I still struggled to see the screen. 

Strike 3. You're out!

I bought a new Viltrox DC-A1 field monitor with a brightness rating of 2,800 nits. HDMI Output from the X-T1 is Playback only, so no joy there. (The X-T3 works beautifully with the Viltrox. More about that in an upcoming blog post.)

What are the take-aways?

A sample size of one proves nothing but as a result of my field test I'm fairly confident in saying the X-T1 is not the best tool in my camera toolbox for time lapsing.

That being said, the X-T1 is still a very useful camera for simple still photography and videography (although I don't shoot enough video to be sure about the latter).

Related Resources 

• More quick-and-dirty video editing using QuickTime Player - a blog post by Walter Sanford
• Blog posts with label "Fujifilm X-T3."
• Why I LOVE the Fujifilm X-T3 Camera (10:14) - a YouTube video by pal2tech (Chris Lee)

Copyright © 2026 by Walter Sanford. All rights reserved.

More quick-and-dirty video editing using QuickTime Player

Two time series of photos were taken during the afternoon on 01 June 2026 using my Fujifilm X-T1 camera and a Meike 6.5mm circular fisheye lens. Apple "QuickTime Player" was used to render JPEG images from each photo set into a time lapse video. Both videos were edited using Apple "Photos."

The entire dome of the sky is shown in the 190° circular field of view: the zenith is located in the center of the image; the horizon is located around the outer rim of the circle. The sky was covered by low level cumuliform clouds and high level cirroform clouds. Notice the wind shear between the lower- and upper clouds.

The "Scene 1" time lapse video was created from 133 photos: first image = 2:43 PM; last image = 3:05 PM. 22 minutes of actual recording time resulted in approximately eight (8) seconds of "raw" time lapse video, given the recording settings I used. Notice the video seems to go into "turbo boost" soon after the start of the clip. I'm not sure how/why that happened.

Scene 1

The "Scene 2" time lapse video was created from 209 photos: first image = 3:07 PM; last image = 3:28 PM. 21 minutes of actual recording time resulted in approximately seven (7) seconds of "raw" time lapse video.

Scene 2

Panorama Photos

The following panoramic composite images were taken using the "Camera" app on my Apple iPad mini 6, set for "Pano" mode. The iPad was mounted on a tripod located in the shade of the tree shown at the top of Scene 2.

 01 JUN 2026. 3:36 PM. Panoramic view. (15009 x 3822 pixels.)

The tree on the left side of the next image is the same one shown in the video.

01 JUN 2026. 3:40 PM. Panoramic view. (15722 x 3734 pixels.)

Tech Tips

The music track for both videos is "Fog Mist" by TrackTribe, available from the YouTube Studio Audio Library.

I plan to use "DaVinci Resolve" to create a movie that includes both video clips featured in this blog post. In the meantime, I wanted to share the preliminary results from the first field test using my Fujifilm X-T1 to capture time lapses. Technical details plus my analysis of the take-aways from the field test will be the topic of a future blog post.

Related Resources

• Quick-and-dirty video editing using QuickTime - a blog post by Walter Sanford
• Blog posts with label "Fujifilm X-T3."

Post update: I think I figured out why Scene 1 seems to go into "turbo boost." I was concerned a three (3) second interval between shots might not be sufficient time for the older camera to write both JPEG and RAW files to a relatively older memory card. Turns out my concern was justified. I looked at the EXIF info for the first 26 photos in Scene 1 and discovered an instance when the time interval between shots is five (5) seconds. (If it weren't such a tedious process then I would have checked all of the photos.) That might have happened more than once, but as I said, I didn't check all 133 photos -- once is enough to cause the noticeable glitch in the time lapse.

Copyright © 2026 by Walter Sanford. All rights reserved.

DaVinci debut

The following video features two time lapse video clips that show the sky over Fairfax County, Virginia USA during the afternoon on 13 May 2026. This is my first video produced using "DaVinci Resolve."

The video looks best when viewed in full-screen mode.

The entire dome of the sky is shown in the 190° circular field of view: the zenith is located in the center of the image; the horizon is located around the outer rim of the circle. The clouds are moving from southwest to northeast across the sky.

Related Resource: Fisheye on the Sky - a blog post by Walter Sanford

Copyright © 2026 by Walter Sanford. All right reserved.

Post update: Two of my friends have been telling me to flip the upside-down tree in Scene 2. (Apparently an upside-down tree caused them to feel cognitive dissonance.) So I flipped the scene.

Scene 2 flipped vertically.

Then my friends suggested both clips should be flipped so the atmosphere appears to flow in the same direction in both clips. So I did.

Both scenes flipped vertically.

Which version do you prefer?

Quick-and-dirty video editing using QuickTime

Simple video editing is as easy as drag-and-drop using Apple "QuickTime Player," as shown in the following example.

"Fisheye on the Sky" | 13 May 2026 | Fairfax County, Virginia USA

The entire dome of the sky is shown in the 190° circular field of view: the zenith is located in the center of the image; the horizon is located around the outer rim of the circle.

The video was created by following these simple steps.

1. Open the first video clip using Apple "QuickTime Player."
2. Drag-and-drop the next video clip on top of the open "QuickTime Player" window.
3. Repeat as often as necessary to add more video clips.
4. Click the "Done" button on the video timeline.
5. Drag-and-drop a music track on top of the open "QuickTime Player" window.
6. Click the "Done" button on the video timeline.
7. Save the edited movie using a new filename.

Video segments are separated by a "jump cut" -- smooth transitions aren't supported by QuickTime. So far I haven't experimented with adding a title screen at the beginning of the movie and a credits screen at the end, but I know it is possible.

How to combine video clips

Source Credit: Google AI.

How to add music to a video

Source Credit: Google AI.

Related Resource: "Fisheye on the Sky" - a blog post by Walter Sanford.

Copyright © 2026 by Walter Sanford. All rights reserved.