Category: Sky Events
Sky events
Mercury at Maximum Elongation
Today Mercury reaches maximum elongation, the furthest point it will reach from the Sun in the sky and the highest it will be above the sunset this apparition. The planet is easily visible as a bright, starlike object about 15° above the setting Sun as the sky grows dark. Over the next couple weeks Mercury will slide back into the sunset, heading for inferior conjunction on Jul 28.
The Moon and Saturn
Saturn, the Moon and Spica will form a trio high in the sky at sunset tonight. The three will be within 7° of each other. The gibbous Moon will be 62% illuminated. Saturn will be shining at 0.4 magnitude while Spica is very close to 1.0 magnitude. Look for the planet Mars 25° west of Saturn at about the same brightness.
The Moon and Mercury
A very thin Moon will rendezvous with Mercury this evening. The pair will separated by about 8° and at the same elevation, over 20° at sunset. The Moon will be a very thin crescent, only 7% illuminated. A little over 5° north of Mercury will be Pollux, with Castor a bit further north, both stars about a magnitude dimmer than the planet which is currently about zero magnitude.
Summer Solstice
Summer solstice occurs today at 13:09HST. Today the Sun will occupy the most northerly position in the sky of the year. The term solstice comes from the latin terms Sol (the Sun) and sistere (to stand still). On this day the Sun seems to stand still as it stops moving northwards each day and begins move to the south. This is the first day of summer as marked by many cultures in the northern hemisphere.
| 2012 Solstices and Equinoxes | ||||
|---|---|---|---|---|
| UT | HST | |||
| Perihelion | Jan 5 | 03:59UT | Jan 4 | 17:59HST |
| Spring Equinox | Mar 20 | 05:14UT | Mar 19 | 19:14HST |
| Summer Solstice | Jun 20 | 23:09UT | Jun 20 | 13:09HST |
| Apehelion | Jul 4 | 23:59UT | Jul 4 | 13:59HST |
| Fall Equinox | Sep 22 | 14:49UT | Sep 22 | 04:49HST |
| Winter Solstice | Dec 21 | 11:12UT | Dec 21 | 01:12HST |
| Source: USNO Data Services Website and the NASA Sky Calendar | ||||
New Moon
Venus and the Hyades
As Venus approaches maximum elongation it will pass through the Hyades star cluster. Because Venus reaches it maximum western excursion on July 1st the planet will sweep out an arc that runs just inside the V-shape of the cluster. Thus the planet will remain within the main body of the cluster for the next 20 days.
Today the planet is only 26′ from εTau at one corner of the V-shaped cluster. On July 8th the planet will pass about 1° from Aldebaran as it exits the cluster at the other corner of the V.
The Moon, Venus and Jupiter
A nice trio will grace the dawn tomorrow, the morning of June 17th. Three bright objects will be visible just before sunrise. A brilliant Venus will be 14° above the horizon at sunrise. Above Venus will be a very thin crescent Moon, only 4% illuminated, will be 4° above Venus. About 8° above Venus will be Jupiter, shining brightly at -2.0 magnitude. Thus Jupiter will be the first to rise, at 04:02HST. Sunrise will occur about 05:43, leaving plenty of time to enjoy this bright conjunction.
Venus Appears in the Dawn
This week Venus will appear in the dawn sky. Today the planet will be over 10° from the Sun at dawn. This will increase over a degree each day as Venus climbs higher into the dawn sky. Maximum elongation will occur on August 14th.
A few nice conjunctions will occur with both Jupiter and the Moon over the coming weeks. Stay tuned to Darker View for postings that will keep you up to date.
Observing the Aureole of Venus
Black drop effect? Bah! I observed a beautiful aureole effect in the minutes leading up to second contact.
The famous black drop effect is seen when atmospheric distortion of the image is quite bad. The effect plagued the early observers attempting to do transit timings. The effect is not seen when the atmosphere allows sharp views of the transit.
Instead, if the seeing is truly good, it is possible to see something far more rare, the aureole of Venus. This is a faint ring of light that has been refracted and scattered through the atmosphere of the planet.
I had not expected to see this, the appearance of the arc of light a complete surprise. But there it was… Very thin, quite faint, a sharp arc of light completing the disk of Venus. The view was steady, with nearly perfect seeing the arc was visible continuously.
Analyzing the observation afterwards I realize it was two elements that allowed me to see the aureole, the excellent seeing offered by the summit of Mauna Kea and good equipment. I was looking through my TeleVue 76mm telescope, using an 8mm Radian eyepiece and a Baader solar film filter. Very good equipment indeed, the optical performance of the system was not going to be a problem.
In the confusion and effort of running the Keck Observatory web stream, I was so glad I managed to free up the few minutes necessary to properly observe second contact. The sight was one of the most beautiful and sublime of any I have witnessed through an eyepiece in my many years of looking through a telescope.
I have been through my photos, nothing captured the faint arc of the aureole, no matter how I stretch the exposure. The best I can do is to record a few drawings in my observing notebook, a poor substitute for the beauty of the real thing…
