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The table shows that the July event, at 9.9 arc minutes, is THE closest appulse that has occurred between these objects SINCE the were discovered. Imagine that. For an image of those objects on July 4th, see Dan Crowson's excellent work at this link and a movie of it here. As an interesting sidebar, he says plate solving that image reveals over 700 galaxies.
It looks like you'll have until about August 9th, 2014, to observe these objects within the 3 degree field of view criteria. After that they move away from each other pretty quickly and will be setting into twilight.
The next telescopically observable appulse won't occur until 2065 and the next appulse CLOSER than this one won't occur until 2134. So if you want to see this kind of rare event, you better get cracking.
A series of visual observations
A series of visual observations
As noted, news of this close approach and the significance therein didn't really register until I started looking into it AFTER Dan took his images. On 14 July, with clear skies and not wanting to miss such a rare event, I set my little Edmund Astroscan on the driveway at my place in Hazelwood Missouri and set out to view this meeting.
My Astroscan is a 4 1/8 inch (105mm) f4.2 telescope. The focal length is 441mm. Using my lowest power, widest apparent field of view eyepiece (Astrotech Paradigm 25mm 60 deg AFOV ), I get a 3.4 degree true Field of view - the edge of view is pretty fuzzy, hence the 3 degree appulse selection criteria.
Finding these objects presented no real difficulty. I observed them for a good 15 minutes and decided how I was going to start the sketch. I'll be using this sketch as the master from which to plot subsequent observations. After initial placement of the asteroids and the reference stars, I used Starry night pro (V6, NOT V7) and the Millennium star atlas to determine that the apparent separation, at that instant, was right at 45 arc minutes. So, consulting the above table, it looks like I observed them at a separation not viewable since 1825.
Weather permitting, I should be able to make a series of observations through the end of July.
In the drawing below, the position for Ceres is marked as "X1" and Vesta is marked "Y1". The reference stars are indicated by A through D and their "HIP" designations are listed on the observing log. The circular drawing area represents the eyepiece field of view.
As you can see from the result, appulses between these two objects occurring within the field of view of a small telescope are pretty rare. Even rarer still are two such appulses occurring in the same year. In fact, over the 400 year search span, it identifies only one year this is true - THIS YEAR!
Here's a screen shot on the right.
For this example, I set the separation criteria to 3 degrees. This is about the maximum field of view for a 4 inch rich field telescope. I also set the search period for 400 years starting on January 1st 1800.
It's a great program and this feature allows you to identify appulses
between various solar system objects.
What's an "Appulse"
What's an "Appulse"
An appulse is an astronomical term that refers to the closest approach of one celestial object to another, as seen from a third body. For more on this type of event, see this definition in Wikipedia.
It seems there was a unique appulse between the asteroids Ceres and Vesta this year. It turns out there were two this year. One in April and one in July. I missed the one in April completely and I'm late on the one in July. The closest "approach" was July 4th with an apparent separation of 9.9 arc minutes. That's pretty close. That's REALLY close!
Ceres was discovered in 1801 by Giuseppe Piazzi. Interestingly, the Dawn spacecraft is set to rendezvous with Ceres in early 2015.
Vesta was discovered in 1807 by Heinrich Wilhelm Olbers.
Even though Vesta is slightly smaller than Ceres, it reflects a bit more light than Ceres so it is usually much brighter than Ceres. This is evidenced by the observation below. In the eyepiece, Vesta was nearly two magnitudes brighter than Ceres.
An aspect of these bodies is that they are visible in binoculars from a dark sky site. They are usually visible from highly light polluted urban and suburban skies using a modest telescope.
How rare is this?
How rare is this?
I wanted to find out how unique this was so I consulted the "Special events" feature in Skytools III.
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