Image credit: NASA/LMSAL
“…image shows Venus on the eastern limb of the Sun. The faint ring around the planet comes from the scattering of its atmosphere, which allows some sunlight to show around the edge of the otherwise dark planetary disk. The faint glow on the disk is an effect of the TRACE telescope.”

To recap an earlier post, a transit is when a smaller astronomical body passes in front of another. We have a rare transit coming up next week, Venus transiting in front of the Sun. There are only two planetary transits from Earth’s viewpoint, Venus and Mercury. Because Mercury orbits the Sun at a faster rate than Venus, we can expect 12-13 transits per century. Venus, on the other hand, transits in pairs 8 years apart in intervals of ~105.5 or 121.5 years (see chart). The last solar transit of Venus was June 8th, 2004. The next one in the pair is June 5/6, 2012. The previous transits were December 1874 and December 1882. After the upcoming transit, the next pairing is slated for December 2117 and December 2125.

Kepler had predicted a transit for 1631 but didn’t predict another for 1639. Jeremiah Horrocks reviewed Kepler’s calculations and determined the possibility of a second transit, which he observed by means of solar projection in November 24, 1639.

In the 1700s, Edmond Halley used the Venus transits as a means of measuring distances in the solar system using Kepler’s third law that states the orbital period squared is proportional to the distance cubed. Halley organized observations at several global observing sites for the 1761 and 1769 Venus transits, realizing that each observer’s line of site would have a slightly different placement on the Sun. By timing how long it would take Venus to transit, he could determine how far away the Sun was from Earth. What’s mind boggling is that the resulting astronomical unit (AU) from that experiment was between 149.67-156.11 million kilometers and we now have a more accurate AU of 149.60 million kilometers.

To help with understanding all this, here are a few definitions/figures that are useful to know:

• A meter (m) is “the length of the path traveled by light in vacuum during a time interval of 1 ⁄ 299,792,458 of a second.” (Bureau International des Poids et Mesures)
• Light travels 299,792,458 m per second (186,282 miles/second) and is known as “speed of light” or simply “lightspeed”.
• Distance from the Earth to the Sun is called an astronomical unit (AU), which = 149.60 million kilometers (92.956 million miles). The speed of light from Sun to Earth (1 AU) = 8.3 min.

Using the ephemeris from my Starry Night program, the AU of Venus from my observing location during the transit from 1706 UT – 2032 UT (sunset) will be 0.2887 AU and from the Sun will be 0.7260 AU.

Screenshot from Starry Night

Another handy tool is a freeware program called WinJUPOS 9.1.8 – Database for Object Positions on Planets and the Sun by Grischa Hahn.

Screenshot of WinJUPOS 9.1.18

Here’s an excellent link taken from NASA’s site for the 2012 Transit of Venus that will be published in Observer’s Handbook 2012, Royal Astronomical Society of Canada. The link provides valuable information on how and when to observe the upcoming transit and from which locations. It also provides the history of the Venus transits and calculator tools for geographic positions. Also see Transit of Venus 2004 as taken from NASA’s site as Published in Observer’s Handbook 2004, Royal Astronomical Society of Canada.

From ALPO: ALPO Astronomy – “Local Circumstances for the Transit of Venus , June 5-6 2012″

Arvind Paranjpye wrote a helpful tutorial on Sketching the transit of Venus 8th June 2004. Peter Grego will also have an article in Astronomy Now magazine June 2012 issue for sketching the transit.

Good luck with your upcoming Venus Transit observations! REMEMBER SOLAR SAFETY: never look at the Sun directly without the use of a proper solar filter. Here are “Six Ways to See the Transit” by Chuck Bueter.

In 2008, SpaceX was hired by NASA to use the DragonLab spacecraft and the Falcon 9 launch vehicle to resupply the ISS after the space Shuttle was to retire. June 2012, SpaceX’s first Falcon 9 successfully orbited Earth. In December 2010, it was the first commercial company to successfully re-enter (and retrieve) a spacecraft from orbit.

Photo credit: SpaceX

After a failed launch may 19, 2012 due to the detection of higher engine chamber pressure readings, the new launch was scheduled for May 22, 2012. Its mission was to demonstrate cargo delivery to the ISS by a privately built spacecraft. Among its cargo, the Dragon is carrying supplies, food and clothing, and lab experiments all weighing ~1200 pounds. As this launch was a test flight, its designed load capability of 7300 pounds was reduced.

Successful lift off was at 07:44 UT at Cape Canaveral as the ISS was crossing the north Atlantic. Dragon performed a series of tests before arriving at the ISS May 25th, 2012, and then was captured by astronaut Don Pettit using a robotic arm to berth it to the Harmony module at 16:02 UT. This marks a historic day being the first privately (commercially) owned spacecraft to dock to the ISS and will certainly pave the way for future transports.

On May 31, 212, the Dragon is scheduled to undock from the ISS and re-orbit Earth, using parachutes to land in the Pacific Ocean off of California’s coast.

• SpaceX Launch Updates
• Launch Manifest

Moon Occultation of Zeta Tauri

Conjunction of Moon,Venus, and Elnath

Venus had a phase of 7% disk illumination with an angular size of 53 arcseconds. The Moon was on lunation 2.11 days with a colongitude of 297.4 degrees.

Labelled Version

Photo details:

Conjunction photo: Canon EOS DIGITAL REBEL XT, F/4, 2.5 seconds, ISO – 1600, 92mm
Occultation photo: Canon EOS DIGITAL REBEL XT, F/5.6, 1.6 seconds, ISO – 1600, 300mm

The Latin word crepuscular means twilight and the term “crepuscular rays” originates from their occurrences during the dawn and dusk hours.

For more information on crepuscular rays and cloud shadows, please visit Atmospheric Optics .

This picture was taken in my front yard during the evening hours just before sunset last night. Texas, USA.

I started off drawing the full solar disk in h-alpha. Four active regions lined up east to west with two more to the south (depicted to the top of the first sketch in the animation). I then made a quick second sketch to use for recording the times and placements of the Moon as it passed between Earth and the Sun.

Quick second solar disk sketch used to record the Moon’s passing and times.

First contact was at 0032 UT. The first marking was at 0035 UT. I set my iPhone’s timer to go off every five minutes until sunset, marking the Moon’s progress each increment with my oil pencil along with the times. In between, Paul and I would alternate using a pair of solar glasses from solarastronomy.org and the views from my double-stacked Coronado Maxscope 60mm h-alpha telescope.

The first image of the animation shows the original sketch in its entirety. Later, I used the second solar disk sketch as a reference to recreate the eclipse on the original sketch with a cut out circular piece of black Strathmore paper. This animation is the result.

And the montage of the scanned sketch with the circular cutout representing the Moon…

As the solar disk became too dim to view (represented in the last couple frames of the animation), I was forced to leave the eyepiece and enjoy the last several minutes with the solar glasses and my camera.

Annular solar eclipse
Photo: NASA Goodard Space Flight Center

It’s time to make the last minute preparations for the annular eclipse tonight/early morning (depending on your location). My location should allow me to see a partial eclipse just before sunset. Traveling 6 hours further west, I would have had a chance to view the annular eclipse, which would certainly be a site to see! Here’s hoping my friends in the path of the annular eclipse has clear skies and the opportunity to witness it first hand. As for me, I’ll settle this time on a partial solar eclipse with my h-alpha solar telescope and a pair of solar glasses.

I plan on doing a set of full disk h-alpha sketches prior to the eclipse and then use them as a template to shade in the Moon as it passes between Earth and the Sun. Of course, this will only work if the clouds stay at bay and I can find a low horizon to view from.

An annular eclipse occurs when the Moon passes in front of the Sun near apogee, the furthest distance in its orbit around Earth. Because of its distance, it is smaller compared to the apparent size of the solar disk and only covers ~88% of the Sun instead of totality. The outer 12% of the Sun creates what looks like a ring of fire surrounding the dark lunar disk. This year, the Moon will pass in front of the Sun only one day after apogee and full annular eclipse will last a few minutes in the USA before it breaks through the ring. The path starts in southeast Asia in the early morning hours and travels 4000 miles to central USA. Partial eclipse will be visible through the more eastern states, but not the states along the Atlantic coastline. The last annular eclipse seen in the USA was in 1994.

Warning:  Please remember that you must view this event with either proper solar filters or special solar glasses, by projection, or grade 14 welder’s masks. Permanent eye damage or blindness can result otherwise.

Helpful links:

• ScienceCasts: Solar Eclipse in the USA
• NASA explains annular eclipses
• NASA’s list of 2012 eclipses, by Fred Espenak
• “JavaScript Solar Eclipse Explorer” – Eclipse Predictions by Fred Espenak and Chris O’Byrne (NASA’s GSFC)
• University of New Mexico site that plans to provide real-time images of the annular solar eclipse
• Shadow and Substance site by Larry Koehn

During the time I observed, a very large prominence off the northeast limb was enlarging and in the process of ejecting as it broke free from the magnetic fields supporting it. I’ve never visually witnessed that large of a prominence breaking away from the Sun before. What really stunned me was how bright it remained over several hours that far off the limb. I grabbed an 8-sketch sequence spanning over 6 hours of the event, not including the full disk rendering I recorded earlier in the day. The last 35 minutes of my session, the prominence became very faint and diffuse. I stopped seeing any connection from the limb after 1717 UT. Of course, that doesn’t necessarily mean there wasn’t, but was perhaps too faint for my tired eyes to see. Please click in the gallery at the bottom of this post to view the entire sequence individually.

Sketches created at the eyepiece with black Strathmore Artagain paper, white Conte’ crayon and pencil, white Prang color pencil, Derwent charcoal pencil, black oil pencil.

There was an coronal mass ejection (CME) recorded between the hours 0137 UT – 0648 UT by SOHO that began with an M5 class flare and reached S2 at its peak, hurling solar protons into space at speeds faster than 1500 km/s (per Spaceweather.com) 1476, in all its glory, has finally reached the western limb and is about to disappear from our view. It went out with a bang. Very condensed, short and slender prominences were in that area and the plage was very bright.

Video credit: SOHO

As of this morning, there were 8 active regions on the Sun. Plage and filaments scattered over three quarters of the solar disk with sunspots popping in and out of view crisply as it moved in and out of the scope’s sweet spot. A large diffuse quiet region filament, similar to the one observed on May 6, 2012, was to the SE quadrant reaching out over the limb. Two large bright prominences were located at PA 70 and 115 with several smaller ones scattered around the limb. The prom at 70 degrees had very faint wisps of structure reaching between the three brightest regions.

I had started to draw the full solar disk when a faint pair of prominences to the NW caught my eye. I had accidentally kicked the adaptor that was plugged into my power pack and the mount turned off, allowing the disk to drift across my field of view. When this happened, a huge billow of plasma floated above the limb. It was attached by very slender lines of plasma to the thick fainter prom at the 315 degrees position angle. It had the appearance of a large balloon being blown to the south while tethered to the ground. Tossing my larger sketchpad to the side, I grabbed the smaller pad and quickly sketched this prom. As the course this morning’s observation went on, the billowed top of the prominence changed quite dramatically. I almost expected it to either break free or collapse on itself before my session ended but by the time I completed the full disk sketch, it was still there.

The prominences near 1476 were dense and compact. The plage was very brightly formed as several slender lines within that active region. The main sunspot in 1476 was very easy to spot in h-alpha although the ARFs were very thin and few.

1479 is reminiscent of 1476 several days ago, although the preceding spot standing alone is on the opposite end. Of course, another difference that the sunspots in 1479 are smaller. They may develop more as the days go on. Here’s hoping for beautiful weather so we can keep an eye on it.

Sketches created at the eyepiece with black Strathmore Artagain paper, white Conte’ crayon and pencil, white Prang color pencil, Derwent charcoal pencil, black oil pencil.

Rainbows are formed by sunlight diffraction within large droplets of water. The larger the droplet, the smaller the diffraction effect that produces a rainbow instead of similar cloud phenomena such as fog bows or glories. The main colors we typically see, starting from the outer to inner bands of the rainbow, are red, orange, yellow, green,blue, indigo and violet with a minute hue of colors in between.

Secondary rainbows are the result of sun rays escaping raindrops after the light has been reflected more than twice inside them. The color order of the secondary rainbow is always reversed from the primary as if mirrored and is more diffuse and widened. Rainbows are always opposite the Sun in the sky. The lower the Sun on the horizon, the taller the rainbow will be.

Les Cowely has a wonderful site for learning more about atmospheric phenomena. Here are a few links within that site to further explain rainbows.

Primary Rainbows, by Atmospheric Optics

Secondary Rainbows, by Atmospheric Optics

Please click PCW Archive for Atmospheric Phenomena for more observations.

2012 05 12, 1315 UT – 1440 UT
Temp: 18.8°C, winds N 10 mph, scattered to 75% overcast, 78% H
Seeing: Wilson 4, Transparency: 5/6, 125x, Alt: 22.3, Az: 081.2

2012 05 13, 1330 UT – 1530 UT
Temp: 21.1°C, winds NNW 7 mph, clear to scattered, 88% H
Seeing: Wilson 4, Transparency: 5/6, 125x, Alt: 41.7, Az: 091.8

Sketches created at the eyepiece with WH Smith white cartridge paper (135 gsm), felt-tipped black artist pen, charcoal pencil, black oil-based pencil and then flipped and rotated to match standard orientation.

1476 continues to put on a show each day. Seeing appeared to be fairly good but when I increased magnification for a close up view of that active region on both days, I struggled to get clear enough definition within it to do a close up sketch (although I made several starts which ended up crumpled to the ground next to my observing chair.) The intricate patchwork of penumbrae was a blast to sketch, not to mention observing the numerous speckles of umbrae within that region. My hat is off to all solar sketchers that were able to capture the scene so well as a close up. It certainly is not an easy region to render, but so worth the effort for an in-depth study. I could easily get lost in that region for hours! The few sunspots that lead to the east out of that region look as if they are trying to grasp at the very last following sunspot to reel it begrudgingly back in.

Seeing was perfect for full disk sketching and lowering magnification to 50-70x really brought out the contrast for plage. Three spots were seen both days in active region 1479. On the 12th, it was easily noticeable how they appeared closer together when nearer to the edge of the limb along with a foreshortening called Wilson’s effect. Penumbrae were observed in the two preceding sunspots with perhaps slight penumbra in the third following spot in that grouping. Faculae surrounded the two following spots and there were lines of facula on either side of the preceding larger spot. On the 13th, the following sunspot was little softer indicating a very faint line of penumbra while the two preceding sunspots showed very definite penumbra, although still a little flattened by foreshortening. The middle sunspot in that group appeared to have a separated umbra, verified later today by the SDO’s continuum image.

There was only one sunspot both days within each active region 1477 and 1478 with umbra and penumbra. They appeared slightly larger than the spots in 1479.

There were quite a bit of faculae on the eastern limb with a small sunspot observed both days. The sunspot had both umbra and penumbra with extreme foreshortening. There is no designation yet that I’ve found for that region.

A wide patch of facula was on the western limb as well, more abundant on the 13th. I believe my placement was off for this patch of facula on one or both of the sketches.