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Sunday, June 03, 2018


Seeing Vesta at Opposition (June 2018)

Evening sky showing the location of the asteroid 4 Vesta on 20 June when at opposition. The view is looking east as seen from Adelaide at 22:00 ACST. Saturn is high above the horizon and Mars is clearly visible. The Asteroid Vesta is visible to the north near Saturn. (click to embiggen, similar views will be seen elsewhere at the equivalent local time).Simulated binocular view of the region near Saturn showing the open cluster M24 and Vesta on Monday June 4 looking east  as seen from Adelaide at 22:00 ACST. Vesta is above M24 and in a direct line with Mu Sag and Kaus Borealis. Similar views will be seen throughout Australia at the equivalent local time (click to embiggen).

The Asteroid 4 Vesta is one of the iconic minor planets, and one of two orbited by the Dawn spacecraft. Importantly at favourable oppositions Vesta is bright enough to be seen with the unaided eye under dark sky conditions.

Black and white binocular chart suitable for printing showing the movement of 4 Vesta over the next 30 days. Click to embiggen and print. 
Alternatively, here is  downloadable  Black and white PDF binocular chart suitable for printing. The large circle represents the field of view of 10x50 binoculars. Use the horizon chart above for orientation first.

This year is one of the best oppositions of Vesta, when it will reach a magnitude of 5.3-5.4 at its brightest. Vesta is at opposition on June 20, and is the best opposition since 2000 (and will not be surpassed until 2029). For those interested it is in a series of oppositions this year (Jupiter May 9, Saturn June 27, and Mars July 27 (best Mars opposition since 2003). Vesta will also pass by some interesting clusters and Nebula.

Vesta will be potentially visible under dark sky conditions. While it is substantially above the magnitude 6 limit for unaided eye visibility, local sky conditions, the number of stars of similar brightness, interference from moonlight and how good your eyesight is may conspire to make it difficult to see. It is however easily visible in binoculars, and if you locate it in binoculars first it will be easier to pick up. You may need to watch it over several nights to see it move and confirm its identity.

On the other hand this year Vesta has some excellent signposts to it, early in June it can be triangulated using Saturn, Mu Sagittarii, the star that forms the “lid” of the teapot of Sagittarius and Kaus Australis at the top of the teapot and the brightest star just above Saturn.

On the 4th and 5th, Kaus Australis, Mu Sagittarii and Vesta are almost in a straight line. Vesta is around half the distance between Mu Sag and Kaus Australis in a straight line north of  Mu Sag above M24.

For the first half of June, sweep north from Saturn until you reach the last obvious brightish star, this is Mu Sagittarii, just beyond and blow this is the obvious and rambling open cluster M24. Just above M24, almost in line with Mu Sagittarii the brightest object visible is Vesta. You may need to watch it over several night to see it move to ensure you have the right object.

From around the 14th sweep up from Mu Sagittarii to the iconic and beautiful Trifid nebula, then sweep across (north) to the dim open cluster M23. Vesta will be near this cluster.
While Vesta will be at opposition on the 20th, it will be brightest from the 19th to 22nd. Unfortunately by then the waxing Moon will begin to interfere, but if you find a large object to block the Moons light out and preserve your might vision, you should have no problems seeing Vesta.

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