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Re: [Phys-L] Ex: Great Conjunction

At the conjunction the visual separation of Jupiter and Saturn will be smaller than the extent of their lunar systems. I’ve found I can get decent pictures of the Galilean moons with nothing more than a camera on a tripod and have been practicing to find the best combination of ISO and exposure time.

Here is a picture I took a couple of days ago of Ganymede, Callisto, Io, and Jupiter, in that order and with Europa hidden in the disk of Jupiter. (800 mm, f/4, 1600 ISO and 1/2 sec)

It’s important to keep the exposure time under a second or the picture will be degraded by sky motion.

John Mallinckrodt
Cal Poly Pomona

On Nov 30, 2020, at 3:37 PM, Anthony Lapinski <> wrote:

I hope everyone had a nice Thanksgiving! I posted this at my school, and
thought I'd share it with the group. I'm getting my telescope ready!
Astronomy is FAR OUT!

Mark your calendar! On December 21 Jupiter and Saturn will appear extremely
close in the sky and will look like a double planet! They will be separated
by only 0.1° - about 1/5 the diameter of the full Moon! It may be
challenging to distinguish them with unaided eyes for some people. In
reality the planets will be much farther apart - 4.8 times the distance
between the Sun and Earth. Jupiter-Saturn pairings/conjunctions are rare
(occur about every 20 years), but they have not been this close in the sky
since the Middle Ages (specifically, on March 4, 1226)!

Look in the southwest skies just after sunset. The planets are low in the
sky and will only be visible for a few hours after sunset. Jupiter appears
bigger and brighter (12x) than Saturn. Binoculars and telescopes will
definitely enhance the view. A telescope will also give you a closer view
of Jupiter's cloud bands, the four satellites that Galileo first saw in
1610, and Saturn's rings which are 21° from edge-on. All within one field
of view! This is shown in the third image here:;;sdata=oniMG3Hk7z%2B4r8fwlC0jIMR6FzuNxwzqIjKMxJYbFnE%3D&amp;reserved=0

Don't miss this rare, historical, remarkable, and spectacular event!

P.S. You don't have to wait until the winter solstice to see Jupiter and
Saturn. They are visible all month. They appear 2° apart (4 moon diameters)
on December 1. Watch them slowly move closer together every night. On
December 16 they'll be just one Moon diameter (0.5°) apart.

P.P.S. The next Great Conjunction is on Halloween, 2040, when these planets
will be 1° apart (two Moon diameters) before sunrise.



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