APOD: Io and Callisto Mutual Event (2014 Nov 26)

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APOD: Io and Callisto Mutual Event (2014 Nov 26)

Post by APOD Robot » Wed Nov 26, 2014 5:06 am

Image Io and Callisto Mutual Event

Explanation: A 24 minute sequence from top to bottom, this intriguing series of telescopic frames tracks the occultation of Io by Callisto, two of Jupiter's Galilean moons, from San Pietro Polesine, Italy, planet Earth. A challenging observational project using a small telescope, the two contrasting Jovian worlds are both slightly larger than Earth's Moon. In fact, bright, volcanic Io and dark, cratered Callisto are about 3,640 and 4,820 kilometers in diameter respectively. With Earth itself now crossing near the orbital plane of Jupiter's moons, astronomers are enjoying a season of Galilean moon mutual events ranging from eclipses to occultations. The series of orbital plane crossings produce a mutual event season every 5 to 6 years.

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Re: APOD: Io and Callisto Mutual Event (2014 Nov 26)

Post by Nitpicker » Wed Nov 26, 2014 7:13 am

Very cool, though presented in a strange orientation. From Earth's perspective, both Io and Callisto are moving in front of and away from Jupiter (which would be above image top), with Io moving faster and passing behind Callisto. These observations would have been in full daylight from Italy.

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Re: APOD: Io and Callisto Mutual Event (2014 Nov 26)

Post by Ron-Astro Pharmacist » Wed Nov 26, 2014 5:29 pm

Nitpicker wrote:Very cool, though presented in a strange orientation. From Earth's perspective, both Io and Callisto are moving in front of and away from Jupiter (which would be above image top), with Io moving faster and passing behind Callisto. These observations would have been in full daylight from Italy.
I remember Astronomy or Sky and Telescope recently running an article on Astrophography during the day but I didn't know how often it is utilized.
It would help to keep circadian rhythms intact. I often wonder how astronomers stay awake and alert when trying to do their research; they must be a dedicated lot. I suppose automation has helped to some degree but some events only happen during the day as you point out.

http://blogs.discovermagazine.com/badas ... g-daytime/
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Re: APOD: Io and Callisto Mutual Event (2014 Nov 26)

Post by ta152h0 » Wed Nov 26, 2014 10:47 pm

omeone should make a cave painting of this, if nothing else, just to annoy our descentants. Lets say in the year 2525...
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Re: APOD: Io and Callisto Mutual Event (2014 Nov 26)

Post by Nitpicker » Thu Nov 27, 2014 2:26 am

Ron-Astro Pharmacist wrote:
Nitpicker wrote:Very cool, though presented in a strange orientation. From Earth's perspective, both Io and Callisto are moving in front of and away from Jupiter (which would be above image top), with Io moving faster and passing behind Callisto. These observations would have been in full daylight from Italy.
I remember Astronomy or Sky and Telescope recently running an article on Astrophography during the day but I didn't know how often it is utilized.
It would help to keep circadian rhythms intact. I often wonder how astronomers stay awake and alert when trying to do their research; they must be a dedicated lot. I suppose automation has helped to some degree but some events only happen during the day as you point out.

http://blogs.discovermagazine.com/badas ... g-daytime/
There are quite a number of these Galilean moon mutual events over the next few months. Jupiter is only visible at night for a few hours before dawn at the moment, but the situation is getting better every day. There will still be some of these events observable at, and after, Jupiter's opposition in February 2015.

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Re: APOD: Io and Callisto Mutual Event (2014 Nov 26)

Post by alter-ego » Thu Nov 27, 2014 5:18 am

I look at this image and, based on personal experience, am blown away by what astronomers can do today.
Today, detailed imaging (from Earth's surface) of the outer planets and their moons can do what a group of us did with difficulty 40 years ago without imaging. In 1974 we used the University of Washington's 30" telescope to acquire photometric light curves of Io occulting Europa. We focused entirely on photon counting; using a multi-stage photomultiplier tube and a chart recorder I recall - no imaging . Gosh, computer punch cards and tapes... From three occultations we generated a low-res reflectivity map of Europa, and determined its radius to be 1483 ± 20 km (we missed it by only ~77km). We published a paper on this work 5 years before the first visit by Voyager 1. Today's Integrating 2D detector arrays seemingly would make this same task so much easier now.

As relatively crude it seems today, that was cool stuff. For me, those were great and still memorable days. Today's APOD brought it all back :ssmile:
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