Mercury at Eastern Elongation

orbital-positions    On Tuesday February 26th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (inferior conjunction) between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun (superior conjunction) and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
   I’ve added Mercury’s orbit to the ‘horizon view’ graphic below. Mercury is never very far ‘out’ from the Sun at elongation because of how close to the Sun is Mercury.
   Currently Mercury is visible over the western horizon at sunset local time. Joining Mercury to the east (up to the left) is the planet Mars. A few degrees west from Mars, (to the right), is the star Hamal. This is the brightest star in the small constellation of Aries the Ram.
   Additionally, if your skies are dark enough it should be possible to see the “Square of Pegasus”, a part of the constellation Pegasus the Winged Horse. And look for the star Mirach, part of the constellation Andromeda the Princess. Just a few degrees to its right is a fuzzy looking smear of light – M-31, the Andromeda Galaxy.

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

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ISS This Evening

   Despite a temperature of 6oF and standing in a couple of inches of snow it was worth it as Venus and Mars shined brightly over my neighbor’s laser light show and I waited patiently for an ISS orbit over my home this evening. This orbit had the International Space Station rising in the northwest and setting in the southeast in a 6-minute visibility that took it nearly to the zenith with its maximum altitude of 85o above the horizon. It’s orbital track had the ISS pass along one side of the ‘Summer Triangle’, the stars Vega and Deneb. As it nears the zenith the ISS will pass very close to the star Alpheratz, the upper left corner star of the asterism “Square of Pegasus”. Alpheratz is actually a star in the constellation of Andromeda the Princess, but it it is commonly used to complete the ‘Square of Pegasus” asterism.

   Camera settings were 18mm; ISO 800; F6.0; 3.2 sec. Pictures stacked using StarStaX. StarStaX is available as Freeware for Mac OS X, Windows and Linux.


Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

Evening Sky Views-ISS

Click on picture to see it full size.

Click on picture to see it full size.

   This evening the ISS flew across my southern horizon from the southwest to southeast and at its maximum visibility reached around 45 degrees in altitude and got to about -3 magnitude. Its path, as the banner graphic shows carried it past the ‘teapot’ asterism of Sagittarius toward the ‘Square of Pegasus’. I took a series of pictures with my fisheye lens with a shutter speed of 5-seconds, F4.6 aperture, and an ISO of 3200. The path the ISS followed started from behind some trees and then behind my big Oak tree. As it emerged on the east side of the tree it faded from view. Near the top of the picture are the three stars forming the ‘Summer Triangle’ asterism, and on the left side look for the ‘Square of Pegasus’.
Click on picture to see it full size.

Click on picture to see it full size.

   So after the ISS faded from sight I aimed the camera straight up toward the zenith and took a few pictures of the ‘Summer Triangle’ asterism. The shutter speed was 5-seconds, with an F4.5 aperture, and ISO 3200. Two smaller constellations, Delphinus the Dolphin and Sagitta the Arrow are in the picture but easy to see in this cropped picture.

   Click here to read about and see additional pictures of the ISS and Iridium flares.

   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Finding Uranus

Click on image to see it full size

Click on image to see it full size

   Okay – the ‘cute’ answer is look behind you, however from an Astronomer’s perspective this may prove difficult so look westward shortly after sunset for the 4 stars making up the asterism The Square of Pegasus and follow the two stars on the left side of the square in a straight line toward the horizon and you will have found Uranus. It is just to the east from another asterism, the Circlet of Cetus the Whale. Uranus is right at the limit of brightness for naked-eye seeing but in binoculars or telescope it is visible as small dot.
   Uranus is located just east of the 0-hour line, the location of the Sun on the March equinox.
Click here to go to the Qué tal in the Current Skies web site for more observing information.

ISS and Uranus

29 December - 6:42 pm CST

29 December – 6:42 pm CST

   After complaining about cloudy skies the other day I got a break last night and had very clear skies. As a result I was able to capture a sequence of images of the ISS flying over my part of the world. I use the Starry Night Pro program to simulate the flight path of the ISS so I can determine where best to aim my camera. My technique is basically to use a wide angle (18 mm) lens and once I determine the appropriate F-stop and shutter speeds I lock the tripod and wait until the ISS appears. Then I take pictures either manually from the laptop or with a digital cable release set to take a sequence of pictures. My preference, however, is to use the utility program that came with the camera. I connect the camera with a USB cable to the laptop and this gives me a real-time view on my laptop computer screen as well as remote control of the camera settings and picture taking. The camera is on a tripod several feet away to reduce any camera jitters.
ISS in Motion

click on the image to see it full size and animated

   During the fly-over the ISS was traveling toward the southeast and crossed the ‘Square of Pegasus’ asterism, and then past the ‘Circlet’ asterism in Pisces coming within a few degrees from the planet Uranus. The images are each 3.2 second time exposures – long enough to capture the dim stars making up the ‘Circlet’ – but also so long in the sense that in 3.2 seconds the ISS has moved enough to show up as a streak of light, like star trails in longer time exposures. This animated graphic is slightly faster than the actual event but I have set it to give a sense of how quickly the ISS moves and how its brightness increase, peaks, then fades.
Click to see this image larger   Looking toward the east were the stars of the Pleiades and, lower toward the horizon were Jupiter and the Hyades. Obviously I couldn’t resist!
   And then this morning there was a neat contrast between the reds and pinks toward the west, the setting waning gibbous Moon, and some high thin cirrus clouds.
Click here to go to the Qué tal in the Current Skies web site for more observing information.