Sunday, September 17, 2017

Kaleidoscope Fun


From time to time, just for fun, I've made a number of kaleidoscopes and holoscopes, mostly from cut-and-stick auto replacement mirrors. These auto mirrors are less expensive than front-surface glass mirrors, and they can be cut with ordinary scissors rather than requiring glass cutting tools and expertise.

My kaleidoscopes are rather ugly when compared with exquisite models made by artistic experts. Mine have no exterior decoration and are held together with masking tape and duct tape. Nevertheless, they produce some nice complicated views. Four of my constructions are shown in the first picture below. From left to right they are: a tetrahedral holoscope, a narrow kaleidoscope with three mirrors, a cubical holoscope, and a three-mirror kaleidoscope which produces a spherical image.
First, consider the cubical holoscope. Five identical small square glass mirrors are taped together with an equal size auto replacement mirror closing the cube on top. Reflecting surfaces all face inward. As you can see in the next picture, I cut away the corners of the top mirror. Three of the missing corners are covered with different colors of transparent plastic. The remaining open corner in the upper left is a viewing hole.
Light entering the cube through the open corners undergoes multiple reflections producing repeated images. Looking through the viewing hole while shining light down on the cube from above produces the following scene.
If I gently press on the slightly flexible top, some lines of multiply reflected images bend.
The tetrahedral holoscope is a 4-sided tetrahedral volume whose sides are equilateral triangles. Each internal surface is a mirror. I cut holes in all four vertices, making the "top" vertex viewing hole the largest. I covered the remaining three holes with red, green, and blue transparent plastic respectively. The next two images are views into the tetrahedral holoscope when it is illuminated by an overhead light along with three additional separate lights pointed at the color-covered vertices.
It looks like the openings with colored plastic should have been bigger because all the colored reflections seem small.

The narrow triangular kaleidoscope produced surprisingly interesting patterns when illuminated from the viewing direction. The next four images were generated by looking at breakfast cereal boxes through the kaleidoscope. Different cereal boxes and slightly different camera tilts produced different patterns.
The last of the four kaleidoscopes produces an amazing spherical pattern. The three sides of the device are cut to specific angles to achieve this effect. The light source is from the same direction as the viewing direction.
Someday I hope to find a way to illuminate the kaleidoscopes from the bottom instead of from the top.

Saturday, September 9, 2017

Sunspot Surprise

Flaring Spot

During recent months while the Sun approached sunspot cycle minimum I've observed a disappointing lack of dramatic solar features. Just in time for August's solar eclipse, however, two significant sunspots appeared and provided nice background markers for that event. Then, two weeks later, more sunspots blossomed, including two major groups nicely placed near center on the solar disc. What a pleasant surprise! All requirements for good observing lined up on September 4th: clear sky, no wind, temperature in the 70's, and good seeing.

Features were distributed across the entire Sun, so it was worthwhile to attempt a panorama capturing the whole scene. The following image is a 48-panel mosaic showing lots of action. Good seeing conditions prevailed throughout capture of 48 video clips, so this is one of the most detailed mosaics I've been able to construct. Sunspot group 2674 is nearly centered on the disc. Sunspot group 2673, threaded with white energetic emissions, is located to the lower right of center. Some smaller white active regions and a few filaments are scattered about. Two significant prominences are visible, including an enormous one at lower left. (Click on any image below for larger views.)
The next 9-panel mosaic shows an enlarged view of the two major sunspots along with a hook-shaped filament.
Next is an individual close view of sunspot group 2674 with multiple umbras stretched horizontally across the image.
The following enlarged view of sunspot group 2673 shows detail in the energetic white emissions threading through the group.
The white threads were continually changing as I watched for more than two hours. They brightened quickly from time to time when minor flares burst forth saturating the camera as you can see in the image below.
Two days after my observations this area emitted two X-class solar flares, the most powerful type of flare. The second flare was the most powerful to appear in eleven years! Auroras appeared as far south as Virginia and North Carolina, but they were truly spectacular in Norway!

The final image shows a close view of the large, curtain-like prominence hanging above the solar limb.
Since sunspot 2673 was changing rapidly, I decided to record a time lapse video of the action. For two hours, from 10:20 to 12:21 EDT, I recorded one video clip per minute. I hope to eventually assemble the 122 still images into a movie of the flaring activity I saw.

Wednesday, August 30, 2017

Solar Eclipse Action

Eclipse Animations

During the August 21st solar eclipse I recorded 49 video clips, some in sequences suitable for time lapse animations. It took several days to organize, align, and process images before I could assemble the "movies" shown here. The individual frames of these animations are grayscale, with no added coloring or other enhancements.

The first animation below shows sunspot group 2671 being covered by the Moon. This is a 7-frame animation spanning 11 minutes, 55 seconds, from 1:36:22 to 1:48:17 EDT.
After eclipse maximum, the same sunspot group was uncovered as the Moon slipped away. The next 9-frame animation shows sunspot group 2671 reappearing over a 14 minute 3 second interval from 3:10:02 to 3:24:05 EDT.
Smaller sunspot 2672 was also uncovered during this 4-frame animation spanning 1 minute 53 seconds from 3:57:39 to 3:59:32 EDT.
Two modest prominences were also eclipsed. Next is a 3-frame animation of the smaller prominence being covered over a span of 1minute 3 seconds from 1:49:01 to 1:50:04 EDT.
The next 3-frame animation features a change of reference frame. Here the lunar limb is fixed, and the Sun moves from left to right relative to the Moon while a prominence is uncovered. This animation shows 1 minute 43 seconds of action from 2:59:28 to 3:01:11 EDT.
Finally, the Moon moved off the solar disc as recorded in the next 3-frame animation lasting only 43 seconds from 4:03:53 to 4:04:40 EDT. The predicted end of eclipse at my location was 4:05:19, so the last frame was recorded only 39 seconds before the Moon left the Sun.
Both Sun and Moon move west to east relative to the stars as seen from Earth. But the Moon moves faster than the Sun. When Moon and Sun align during a solar eclipse, we see the Moon passing the Sun, overtaking the Sun, moving west to east relative to the solar disc. We all know Earth orbits the Sun and the Moon orbits Earth, but we don't often get a chance to see this orbital motion displayed so obviously in only minutes of observation!

Sunday, August 27, 2017

Solar Eclipse!

A Special Day

The solar eclipse on August 21st was only partial at my home in Williamsburg. From my back yard, at maximum eclipse, 88 percent of the solar diameter was blocked, and 85.6 percent of the solar area was covered. Years and months before the eclipse I debated the merits of traveling somewhere to be in the path of totality. If I traveled, I wouldn't take my solar telescope. I would experience totality, but probably not get any worthwhile images. If I stayed home, I could try using my telescope to get hydrogen-alpha images of the lunar limb covering solar features. In the end, I decided to stay home and see how my telescopic imaging system would perform.

Several weather forecasts predicted nearly clear skies for August 21st. I set up my equipment hours before noon to be well prepared for the afternoon eclipse. I also wanted to get images of sunspots on the solar disc before the Moon came on the scene. Fortunately, a major sunspot group was located near center on the solar disc along with another smaller group near the western limb. These provided nice background features for the Moon's limb to cover during the eclipse. The Sun had often been nearly featureless recently, so the appearance of these sunspots was an unexpected bonus.

As often happens, predictions of cloud coverage were inaccurate. Near 10:00 am EDT several drifting clouds were present, but not enough to make imaging impossible. At 10:14 I captured the following image of large sunspot group 2671 near center on the solar disc. Lots of complex structure is visible. (Click on any image below for larger views.)
Clouds soon increased. It became harder to find clear gaps large enough to get an unobstructed view. I had to wait 35 minutes before getting one chance to capture the other sunspot, 2672, seen below.
At this point things looked bleak for viewing the afternoon eclipse! I shut down my equipment and had some breakfast.

Two hours later my telescope and computer were powered up and ready to go for the beginning of the eclipse. Clouds with gaps drifted across the sky. The Sun crossed the meridian at 1:10, so I waited until then before locking the telescope on the Sun. (This avoided an inconvenient meridian flip required by my German equatorial mount.) The first appearance of the Moon's black disc on the Sun's edge was scheduled at 1:20. I wasn't quick enough to capture this event. My first image at 1:26 was unremarkable, but 18 minutes later, at 1:44, the Moon's edge appeared just to the right of (west of) the largest umbra in sunspot group 2671 as shown below.
Seven minutes later the lunar limb (moving right to left, or, eastward) had passed the large umbra and moved over erupting white energetic emissions shown in  the next picture.
By comparing the two previous images you can see how much the Moon had moved in about 7 minutes. The Moon's eastward motion relative to the Sun was easily visible in real time on my laptop screen as smaller solar features were continuously eclipsed. This was a rare opportunity to witness lunar orbital motion with only a few seconds of observation!

I wondered if lunar motion would smear out detail along the lunar limb. This turned out to be true. Most of my video clips were limited to 400 frames which took about 11 seconds to record. The image processing software I use to produce still images from the video clips did a good job with relatively steady solar features, but detail along the lunar limb was not resolved. The software produced a thin bright border along the moving lunar limb.

I thought an image of the lunar limb crossing a sunspot umbra would be interesting. Unfortunately, a big cloud blocked the Sun at the moment this crossing occurred. So I have only before and after crossing pictures above. By the time clouds thinned somewhat, the entire sunspot group had been covered, and the lunar limb was moving over bland surface features.

Two modest prominences were present on eclipse day. Another interesting image, I thought, would be the lunar edge crossing a prominence on the Sun's limb. The next image shows one such event where you can see the Moon's limb extending beyond the solar disc.
My daughter's family, one of her friends, and some of our neighbors also viewed the eclipse with me. I was so happy to share my astronomical enthusiasm for a couple hours. In the next image my daughter is looking through eclipse glasses while I'm watching a magnified telescopic hydrogen-alpha view on a laptop screen. The laptop is shaded by a cardboard box, and I'm shaded by an effective clamp-on umbrella recently purchased.
My little granddaughter, Annabelle, was happy to play for a while on her blanket. You can see the partly clouded sky in the background.
My other granddaughter, Sophie, pronounced eclipse views, "Cool!". She shared a view of my laptop screen and also saw the entire solar disc in hydrogen-alpha through my telescope. Not many 7-year-olds can claim the same experience.
Of course, we had to try the old "colander" trick showing multiple crescent images of the nearly maximum eclipsed Sun. I had never noticed the appropriate star-shaped hole pattern before.
We had two pairs of solar filtered binoculars, eclipse glasses, the telescope, and various pinhole devices. My son-in-law had fun looking through all the various optical instruments.
Sophie and her close friend, Portia, shared a view through filtered 100X25 binoculars.
Eclipse maximum happened at about 2:46. The sky became noticeably dimmer for a short while near this time. Soon after maximum clouds began to thin and seeing became much better as the atmosphere steadied. At 3:00 I captured the following view of the largest solar prominence being uncovered by the receding Moon. (The Moon is moving from right to left here.)
Ten minutes later I could see large sunspot group 2671 being uncovered as the Moon continued moving eastward across the Sun.
Fourteen minutes later all of sunspot group 2671 was uncovered.
Just before 4:00 sunspot 2672 was completely uncovered.
The Moon's "bite" on the Sun was rapidly diminishing. At 4:04:40, just 39 seconds before the predicted end of eclipse at my location, I captured this final view of the lunar limb leaving the Sun.
After the eclipse I felt exhilarated, but also completely exhausted. Heat drains my energy. The temperature had been in the low 90's since noon. My shirt was soaked through, especially after hauling all the equipment inside. I could barely keep my eyes open for the rest of the day, including during a dinner to celebrate C's birthday, which, coincidentally, also fell on eclipse day!

I might be able to use some of the many images not included here to create an animation showing the Moon covering the large sunspot group. Perhaps I'll include that in my next post.

Monday, July 10, 2017

Double Feature!

Prominence and Sunspot

An enormous prominence was suspended above the Sun's eastern limb on July 8th. Nearby was a growing active sunspot. The sky, rarely clear during July, was cloudless, so I seized the opportunity to image these dramatic features. Only brief puffs of gentle breeze gave any relief from the heat with temperature at 85 degrees while I worked.

The first image below is a 14-panel mosaic made with a 5X Barlow lens. It shows the Sun's eastern side with sunspot 2665 and several prominences along the limb. (Click on the image for a more detailed view.)
The next image is a closer view of the largest prominence and sunspot 2665. White energetic emissions erupt in the middle of the sunspot group. The giant prominence is several Earth diameters high.
It's hard to work comfortably in humid July heat. My shirt was soaked with perspiration after only 35 minutes. More than three months have passed since the last time I used my solar telescope. It may be months again until conditions are right for another solar imaging session.

Tuesday, June 6, 2017

Double Shadow Transit on Jupiter

Three Moons and the Red Spot!

Orbiting Jovian moons sometimes pass in front of Jupiter and sometimes behind. When they pass in front, it's possible for their shadows to fall on Jupiter. There have been several recent opportunities to see two of these shadows on Jupiter at once! Unfortunately, it was cloudy at my location every time. Finally, on June 3rd, conditions were good enough to try observing this interesting phenomenon. Scattered clouds filled the sky as I set up my telescope. As darkness fell, clouds diminished leaving a slightly hazy sky. With no wind, and temperature at 74 degrees, it was very comfortable working outside at the telescope. Jupiter was about 1.5 degrees below the 75 percent illuminated Moon, forming an attractive pair.

I captured the image below at 10:15pm EDT, just after the first shadow entered Jupiter's disc. Two moons visible to the right of Jupiter are Ganymede and Callisto, with Ganymede above Callisto. Another moon, icy Europa, was left of Jupiter, but too dim to show in any images I took. The final Galilean moon, volcanic Io, cast the black shadow seen below. Io itself was located directly in front of Jupiter's disc to the right of the shadow. Consequently, Io is hard to distinguish from bright background planetary features in this image.
At 10:21pm EDT Ganymede's shadow can be seen making a small, black entrance notch in the upper left of Jupiter's disc.
Ten minutes later, at 10:31pm EDT, Ganymede's shadow was still entering the disc. Notice the small, pale red spot nearly centered in the bottom white zone.
In another 10 minutes, at 10:41pm EDT, Ganymede's shadow had fully entered the Jovian disc. An observer sitting within one of these shadows on Jupiter would see the Sun eclipsed by a Jovian moon!
In the next image, taken 30 minutes later at 11:11pm EDT, you can finally see the tiny white disc of Io about to exit the dark belt on Jupiter's right edge.
At 11:21pm EDT, Io had completely exited the Jovian disc and was now clearly visible on the right against a black sky. Jupiter's great Red Spot was also rotating into view on the lower left edge.
My hopes of following shadows entirely across the disc were dashed by increasing haziness over the whole sky. Jupiter was also getting closer to the horizon. Soon, a bright 22-degree circle formed around the nearby Moon. I had to increase my exposure times as Jupiter began to fade behind the thickening haze. My last image, at 12:01am EDT, June 4th, shows the Red Spot, two shadows, and three moons! Wow!
I made a time lapse animated GIF using 14 images recorded between 9:41pm EDT and midnight. This little video compresses 2 hours and 20 minutes of Jovian motion into about 2 seconds. Jupiter rotates, moons orbit, and shadows transit the disc!
By the time I got to bed after 1:00am, I was exhausted. My 52-mile bike ride the next morning completely wiped me out. But it was worth the effort to record this beautiful celestial event! 

People say I'm crazy doing what I'm doing
Well they give me all kinds of warnings to save me from ruin
When I say that I'm o.k. well they look at me kind of strange
Surely you're not happy now you no longer play the game

People say I'm lazy dreaming my life away
Well they give me all kinds of advice designed to enlighten me
When I tell them that I'm doing fine watching shadows on the wall
Don't you miss the big time boy you're no longer on the ball

I'm just sitting here watching the wheels go round and round
I really love to watch them roll
No longer riding on the merry-go-round
I just had to let it go

John Lennon