World War I Airplanes

Old Warplanes

During my annual visit to the Military Through the Ages exhibition this year at the Jamestown Settlement Museum I came across two displays I'd never seen before. First was a French biplane shown below.

This plane was armed with a machine gun whose firing mechanism was synchronized with the propeller so bullets wouldn't destroy the blades.

The fabric and wire construction of these planes seems incredibly fragile compared to modern fighters. Cloth and wire weren't much protection from machine gun bullets! Nearby was a German plane from the same war.

A smaller machine gun fired forward from the German plane.

Cockpit controls seem extremely primitive!

The German plane was a Fokker E3 whose features are described below.

Among the many reenactors attending this year's exhibition was a group portraying The Devil's Nightmare Regiment from roughly the year 1529. They always present a colorful display of weapons, costumes, and living customs from this time period. I found their recruitment poster particularly amusing.

It's always a pleasure to visit this wonderful exhibition each year, especially on a mild sunny day!




   

Magnetic Tensegrity Table

Nice Physics Showpiece!

I recently discovered a new physics toy to add to my collection. The beautiful Magnetic Tensegrity Table is shown below. It's made in Britain and comes unassembled in a small box.

The height is about 5 inches, just under 13 centimeters. Many parts and screws were extremely small. They challenged my diminished dexterity during assembly. But the assembly instructions were excellent! In fact, I've never seen a better illustrated, clearly worded, step by step assembly guide!

So how does it work? Three vertical wires evenly spaced around the edges of the circular base and top are under tension. The wires can't support a load by compression, so they are not supporting the top. The small powerful magnets suspended by hooks are attracting each other and would seem to draw the red top and base together. So how does the top stay up?

The curved silver magnet supports are the key. Look at the upper magnet. It is pulled down by the attraction of the magnet below. The downward force on the upper magnet presses its (left) silver support down onto the red base. Now look at the bottom magnet. It is pulled up by the attraction of the magnet above. The upward force on the bottom magnet presses its (right) silver support up against the red top. So the base is pushed down while the top is pushed up! That's why the wires are under tension!

There's enough lift on the top to support extra weight. The next picture shows a 200 gram mass resting on the table top! 

The manufacturer suggested the table would hold up to about 260 grams before collapsing. I foolishly tried 300 grams, and, yes, the whole thing collapsed! It wasn't easy to separate the magnets and reassemble the table, but, after an hour or so, I eventually succeeded. I'll stick to the 200 gram mass from now on. 

Refractor With New Camera

Sky Is Too Bright

I've been impatient to see how a new Nikon Z6 2 camera would work when attached to my 130 mm Stellarvue refractor. Although sky conditions were poor on March 4th, strong winds had diminished, and it wasn't terribly cold. A 94 percent full Moon was present, but I decided to haul out my equipment and see what kind of images were possible. Before sunset I set up the telescope and camera as shown below.

It takes quite a while to assemble the tripod, balance the telescope, hook up the electrical connections, and set up a laptop computer. I used a star diagonal with the camera instead of a straight through attachment because, otherwise, it would be hard to see the camera viewing screen with the scope pointed near the zenith.

The temperature had fallen to about 52 degrees a few hours after sunset, but bright moonlight filled the sky with natural light pollution. I took this single shot 1/60-second picture of the Moon at ISO 100 using a 2X Barlow lens:

I quickly discovered how bright moonlight, neighborhood lights, and lack of flat field frames made all my pictures nearly useless at first inspection. For example, look at this image of the Pleiades star cluster constructed by stacking sixteen, 4-second exposures with ISO set at 51200.

Notice how the background sky looks blue instead of black. Also, notice the bright circular central region caused by uneven illumination of the camera sensor. A flat field frame (image of a uniform light source) would record uneven illumination and allow me to eliminate it. But I didn't record a flat field frame. It took hours of image processing to reduce initially awful unnatural colors. I also cropped out obvious vignetting around the outer edges of the original image. The central circular glow is an image flaw, but the hazy silver glow around three bright stars near the bottom is a hint of real reflection nebulosity.

One of my neighbors had a back yard floodlight shining directly on the telescope from two houses away. This made it impossible to photograph the flame nebula in Orion. All trial images had strange colors and light arcs caused by reflection of the floodlight in the telescope tube. Eventually, Orion rose high enough to avoid unwanted reflections and I was able to get the following picture of the Orion Nebula by stacking two, 15-second exposures at ISO 6400.

It took many attempts of trial and error image processing to correct erroneous colors and reduce the effects of sky brightness. You can still see evidence of vignetting and a hazy remnant of light pollution in the previous image. I think I can do better with longer exposures on a darker night.

I pointed the telescope at two star clusters hoping they would show up reasonably well in the bright sky. The image of cluster M37 in Auriga shown in the next image is disappointing because star colors don't seem correct. This image is a stack of twelve, 5-second exposures at ISO 51200.

Inaccurate colors are even more evident in the next image of cluster M35 in Gemini. Smaller, more distant cluster NGC 2158 is visible above M35. This is a stack of 24, 5-second exposures at ISO 51200.

Other star images I've made with this camera under darker skies with different lenses have produced accurate star colors. I'm guessing the camera's white balance was possibly thrown off by bright moonlight and the neighbor's floodlight. Looking back at pictures with correct star colors I noticed how histogram plots for separate red, green, and blue channels significantly overlapped. In these latest incorrectly colored images, however, the red, green, and blue histograms didn't overlap at all! Eventually, I discovered a way to make color corrections using Photoshop. These corrections made the three histograms overlap more. Yet, true colors didn't seem fully restored. I also wonder if I set ISO values too high. I'll have to experiment more when the sky is darker.

After a while I inserted a 2X Barlow lens and tried capturing other celestial targets. All the pictures below were made using the 2X Barlow. Galaxies M81 and M82 in Ursa Major are only about 37 arc minutes apart, so I thought I might fit them in one field of view. For this shot the telescope pointed away from the annoying floodlight and away from the bright Moon. This is a stack of ten, 6-second exposures at ISO 51200. M81 is in the lower right and M82 is in the upper left.

Faint traces of M81's spiral structure are visible, but background sky brightness and short exposure times don't permit visibility of dim details. I'd like to try this again with better conditions. Although the telescope was tracking sky rotation, tracking was inaccurate due to poor polar alignment. Inaccurate tracking limits exposure time. I still don't have a quick, efficient way to get good polar alignment with my non-permanent mount. I found elongated star images in exposures longer than about 8 seconds. If I want to improve image quality, I'll have to find some solution to the polar alignment problem.

Another group of closely spaced galaxies is located in Leo. The next image shows M65, M66, and NGC 3628 together. This is a stack of eight, 8-second exposures at ISO 51200.

Faint edge-on galaxy NGC 3628 is in the upper left, M66 is in the upper right and M65 is below center. Once again, hints of faint spiral arms are present.

Globular cluster M3 in Bootes had risen far enough above the horizon to make the next image possible. This is a stack of eight, 8-second images at ISO 51200.

Finally, planetary nebula NGC 2392 in Gemini is visible in the next picture made from a stack of ten, 6-second exposures at ISO 12800. The 2X Barlow didn't provide enough magnification to show much detail. I also wonder if the color is accurate.

Temperature had dropped to about 47 degrees just after midnight. I was getting tired and chilled, so it was time to quit. All the equipment was bone dry! There was not one drop of dew! Other conditions were imperfect, but I couldn't complain about dew! After I took everything apart and hauled all the gear inside, just as I was closing the door, my neighbor turned off the blasted floodlight!

Departing Sunspots

Afternoon Session

My last solar imaging session was months ago in October!  Thereafter, most days were cloudy, or too cold, or too windy. Finally, on February 18th, a clear day arrived without strong wind or freezing temperature. I waited for afternoon to let temperature rise into the mid-40's and began imaging at 1:45 pm EST. Seeing was mediocre. There were no dramatic prominences, and most sunspots were located in the Sun's western hemisphere where they were destined to depart in the next few days by rotating out of view. The first image below is a 12-panel mosaic showing features in the western hemisphere.

Four sunspots are visible above. The most prominent one is sunspot 3226 in the northwest quadrant. In the southwest quadrant, from left to right, are sunspots 3220, 3217, and 3225. A few dark filaments appear on the disc.

Major sunspot 3226 with a light bridge across the umbra shows up well in the next close image. View it at 100 percent to see all the detail present.

Sunspots 3220, 3217, and 3225 also look nicely detailed when viewed at 100 percent in the following image of the southwest quadrant.

Sunspot 3217 is accompanied by a fan-shaped filament. Sunspot 3225 is closest to the limb where its neighboring white energetic region will rotate out of sight before the following umbra. Sunspot 3220, on the left, has a single umbra.

One other sunspot of note, 3229, was in the eastern hemisphere. It had emitted a powerful X-class solar flare just a day or two before. On February 18th, however, it appeared like this:

Evidence of 3229's eruptive nature remains in the image above. A dark filament arches above a white active area to the left of the umbra. Shooting straight up are narrow spiky eruptions emerging from the left-most white energetic area. View the image at 100 percent to see this best.

These images turned out remarkably well in spite of sometimes unsteady afternoon seeing. All images were made by stacking the best 400 frames from 4,000-frame videos.