Author Topic: Venus/Jupiter conjunction  (Read 1499 times)

sgottlieb

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Venus/Jupiter conjunction
« on: August 27, 2016, 09:16:21 PM »
Hope some of you had a chance to view the very close conjunction of Venus and Jupiter this evening after sunset.  Beautiful naked-eye and quite striking to see both objects fairly close together at low power in a telescope.  We've had thick fog in Albany in the evenings nearly every day for several weeks, but tonight there was a totally clear window low in the west!

-- Steve

mccarthymark

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Re: Venus/Jupiter conjunction
« Reply #1 on: August 28, 2016, 10:27:48 AM »
We were able to see the conjunction last night from Fremont Peak.  Pat Donnelly picked it out with binoculars in the sunset glow and helped us point our scopes to it as it was not yet naked eye (mine was a 10-inch).  The smoke haze was pretty thick; in the scope Venus was bright enough but Jupiter was positively purple, I could barely make out its bands, and only just before it set did I get an averted vision glimpse of one of the moons (although I was on low power, 35x).  I could eventually see Venus naked eye but not Jupiter.  We treated the public night visitors to the view until it set.  When I first saw a Venus/Jupiter conjunction a couple years ago I was struck by how "large" Venus appears next to Jupiter.  It was the same last night, and many of the guests were amazed by the size comparison too.
Mark

sgottlieb

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Re: Venus/Jupiter conjunction
« Reply #2 on: August 28, 2016, 02:47:28 PM »
Mark, perhaps I'm misunderstanding but Venus is only 11" in diameter (more than 90% illuminated) while Jupiter is 31", so Venus is currently only 1/3 as large as Jupiter.  Venus can appear over 60" when it's a very thin crescent and certainly larger than Jupiter (maximum about 50" at opposition).

-- Steve

mccarthymark

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Re: Venus/Jupiter conjunction
« Reply #3 on: August 28, 2016, 06:02:23 PM »
Hi Steve, sorry I wasn't very clear. 

I was trying to relate the disorientating difference in scale seen in the conjunction.  Most people know Jupiter is the largest planet and expect it to be so; but seeing Venus with it in the same view, it is strange to see Venus larger than one would expect it to be.  It's kind of a shock and takes a minute to reason oneself through the explanation (how large Jupiter really must be given how much farther away it is, and so forth).

When I wrote "it was the same" I was thinking of this feeling of dissonance rather than the sizes being the same as what I had seen before.

I think another factor was I was at low power (35x) so the disk sizes were smaller making it more difficult to judge sizes.  Jupiter's disk was plainly seen, but Venus' wasn't as clean, refracting through  the atmosphere and with some diffraction spikes in the view.  A lot of the guests didn't refocus when they looked through the scope so the images may have been poor.  All of this making it harder to make a really good comparison.
Mark

sgottlieb

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Re: Venus/Jupiter conjunction
« Reply #4 on: August 28, 2016, 06:24:20 PM »
It would have been cool if Venus WAS a thin crescent -- that really would have caused some disorientation with the general public and confusion with the moon!

MattT

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Re: Venus/Jupiter conjunction
« Reply #5 on: August 29, 2016, 04:40:54 PM »
Here's an image I captured about a half hour after the moment the two planets appeared closest together (is that called the "appulse?"), Taken through the 8" refractor at Chabot Space & Science center with my Samsung Note 7.

You can see Jupiter's apparent size is much larger. At the eyepiece we glimpsed banding at times on Jupiter, but sky conditions were not great and I didn't capture any detail with the phone. You can just make out the gibbous phase of Venus, though!

MT
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DDK

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Re: Venus/Jupiter conjunction
« Reply #6 on: August 29, 2016, 07:13:00 PM »
Looks like you caught the Ghost of Jupiter.
TAC - astro anarchy at work <*>

MattT

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Re: Venus/Jupiter conjunction
« Reply #7 on: August 30, 2016, 08:38:00 PM »
Ha! I thought the same thing while looking at it live.
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Matt Tarlach
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