Nov 052017

Although the bottom portion of this image is largely Mare Imbrium (The Sea of Rains) what I was concentrating on was catching sunrise in the large circular area towards the top and just right of center. This area is Sinus Iridum (The Bay of Rainbows). The ‘bay’ is a 236 km (146 mi.) crater that predated the impact that formed Mare Imbrium. The crater was flooded by basaltic lava that resulted from the much larger Imbrium impact.

There are very few named craters in the bay, but several surface ridges called dorsa are visible. A dorsum is a ridge formed when the lava cools and contracts.

To put the size of the ‘bay’ into perspective, this is a 146 mi. wide circle centered on Niceville, FL.

Sinus Iridum, along with most large features of the Moon, were named by Giovanni Battista Riccioli (1598-1671). Riccioli was an Italian Jesuit priest who included the names as well as detailed maps of the Moon in his seminal work, Almagestum Novum (New Almagest). Published in 1651 and consisting of 1500 pages, the work was used as an astronomical reference for many decades. His names and naming conventions are still used today.

 Posted by at 13:40
Sep 222017

As many of you know the OSIRIS-REx spacecraft made an Earth gravitational assist fly-by today. The spacecraft needed the slingshot maneuver to make it to its rendezvous with the asteroid Bennu in August 2018. The spacecraft will orbit the asteroid for up close study, then drop low enough to grab a sample of the surface for return to the Earth in September 2023.

NASA put out a call to amateur astronomers to take images of the spacecraft as it approached the Earth. So, for the past week I have been attempting to do just that. Last night the spacecraft was finally bright enough for me to catch it in a series of exposures. Even so, the speed, brightness and size of the spacecraft makes it very difficult to see.

The above image is the third of eight 300 second exposures that I was able to get before the clouds closed in. The circle shows the location of the automobile sized craft which should give you an idea where it will be in the following animation. The craft’s motion is from upper right to middle left.

I had to stretch the images as well as invert them to make the faint streak a little more visible. This close to the Earth the apparent velocity of OSIRIS-REx is obvious.

[Update: 03 Jan 2018] OSIRIS-Rex is now projected to arrive at Bennu in December of 2018. Approach operations will begin in August.

 Posted by at 14:37
Sep 152017

This morning the Cassini spacecraft entered the atmosphere of Saturn and ultimately became part of the planet it was sent to study.

Artist rendering of Cassini’s atmospheric entry.
Credit: NASA/JPL

The spacecraft entered orbit around Saturn on the 1st of July 2004 after a six year trip to the planet. It has been studying Saturn and its rings and moons since that time. One of the first things the spacecraft did was to deploy the Huygens probe toward Saturn’s largest moon, Titan. The probe became the first lander on a solar system moon other than our own.

Artist rendering of Huygens’ landing on Titan. Credit: NASA/JPL

Image from the surface of Titan. Credit: ESA/NASA/JPL/ University of Arizona

There are too many discoveries over the 13 years Cassini spent in the Saturnian system to list. Probably the most surprising was the discovery of geysers erupting from the southern pole of the ice covered moon Enceladus.

Geyser plumes from the southern pole of Enceladus. Credit: NASA/JPL

Subsequent study has revealed the material being ejected from the moon to be salty water carrying organic molecules. This implies the conditions necessary for life exists in the outer solar system in a place scientists never expected.

In addition to the scientific discoveries is the vast archive of images that Cassini took. The beauty of the planet and rings was worth the investment.

Saturn as seen by Cassini.
Credit: NASA/JPL

To the entire Cassini/Huygens team, thank you. Well done.
 Posted by at 10:24
Aug 202017

Last night I took images of a comet. My standard exposure length of 300 seconds was too long and during that period the comet moved enough to smear into a streak rendering the images useless for analysis. The video is an animation of 11 300 second exposures and shows the amount of movement over 55 minutes. In this case, North is to the top.

Currently, the comet is between Mars and Jupiter and above the plane of the ecliptic but headed south to where most of its orbit lies.

I will try a different tracking technique and exposure duration later tonight to see if I can get accurate astrometric data to report to the MPC and to get a prettier picture of the tail.

 Posted by at 13:34
Jul 042017

After wrapping up the last JunoCam series on the 1st I noticed that the Moon was in a good position to get some terminator images. The Moon’s terminator is the line dividing the daytime side of the Moon from the nighttime side. So, at the terminator, the Sun appears to be rising. This puts the light from the Sun hitting that area of the Moon at a very low angle. At that low angle, mountains and crater walls cast long shadows providing a noticeable 3D effect.

The image below is a heavily cratered area of the south central section of the Moon. The large, deeply shadowed crater towards the top center of the image is crater Maginus. A notch in the crater wall allows a beam of sunlight to spear into the shadows illuminating an area of the crater floor.

Also visible toward the bottom, again deep in shadows, is a crater rim just catching the rising Sun. In fact, the illuminated rim looks like a sickle with the pointed end angled to the right. This is the rim of crater Hell. No, not that Hell. The crater is named for the Hungarian astronomer and Jesuit priest Maximilian Hell. He was appointed director of the Vienna Observatory in 1756.

Map generated with Virtual Moon Atlas

The next image is from a little farther north. The dark area to the lower left is the southern portion of the Sea of Tranquility. Of note in this image are the two rilles toward the bottom center and right. A rille is a long narrow depression that looks like a channel. The horizontal rille at center bottom is Rima Ariadaeus. Rima is the latin name for a rille. Rima Ariadaeus is over 180 miles long and was formed when the surface of the Moon pulled apart at parallel faults and the section of crust between sank.

The other rille, Rima Hyginus, is split into two sections by the crater Hyginus. However, this crater is not an impact crater. It is a volcanic caldera. So, the associated rille is thought to be formed by ancient collapsed lava tubes. It is most visible in the section to the right of the crater. Upon close examination it appears the roof of the tube collapsed in a series of connected craters.

Map generated with Virtual Moon Atlas

Also visible in the above image are the landing sites for Apollo 11 and 16. Apollo 11 is in the southern part of The Sea of Tranquility along with the three craters named in honor of the crew members. The Apollo 16 landing site is further south just to the right of the small but prominent crater Kant which is right of the largest crater Theophilus.

 Posted by at 16:18