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Saturn's apparent magnitude from Uranus is +3.228. Jupiter orbits closer to the sun than Saturn. Can we therefore expect Jupiter’s apparent magnitude from Uranus to be dimmer than Saturn's, or is it in fact brighter?

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    $\begingroup$ In the light of the similar previous questions and their answers: please use the general adivice and strategy given there and /or consult a programme like Stellarium to give you these simple look-up answers. $\endgroup$ Commented Nov 27, 2021 at 14:58
  • $\begingroup$ @planetmaker. I have had a look at that app and I don't understand it. In other words, I don't know how to operate it towards desired goal. $\endgroup$ Commented Nov 27, 2021 at 15:03
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    $\begingroup$ "Saturn's apparent magnitude as watched from Uranus is +3.228\. Is it? I'd think it would vary a lot and not be a fixed number. Where did you get +3.228? $\endgroup$
    – James K
    Commented Nov 27, 2021 at 17:40
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    $\begingroup$ @James K. astronomy.stackexchange.com/questions/47458/… $\endgroup$ Commented Nov 27, 2021 at 21:48
  • $\begingroup$ 22/9/23 result of Jupiter seen from Uranus = 2037, 2051 and 2120 = -0.93 $\endgroup$ Commented Sep 22, 2023 at 12:50

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I started Stellarium on my computer and pressed F6 to bring up the "Location" window.

Then I changed the planet to "Uranus", and marvelled at the view of the many rings and many moons from the planet's "surface"

For convenience I clicked the buttons to remove the ground and the atmosphere. then I found and clicked on Saturn. It had a magnitude of 3.74. I then pressed F5 to get a time window and stepped one month at a time while watching the change in Saturn's brightness. The maximum I could get was +3.55 (in 2042) though it is believable that it could get brighter at a more favourable elongation in it's elliptical orbit. I also noted that as Saturn passes in front of the sun, its magnitude gets much less, well below naked eye.

I then repeated with Jupiter. It has a maximum brightness of +1.55 (in about 2031) but again, it is believable that it would be brighter at a more favourable elongation.

At its brightest, Jupiter is a lot brighter than Saturn when viewed from Uranus.

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  • $\begingroup$ I just downloaded the Stellarium Plus app. Had to pay $14.99 for it. I don’t know how to use it. Could you please guide me through it. $\endgroup$ Commented Nov 27, 2021 at 22:47
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    $\begingroup$ You were robbed. Stellarium is free software for Windows, Mac and Linux. stellarium.org I hope the step by step in the above answer would enable you to check the answer. The use of "F6" and "Window" should have made it clear that this isn't a mobile app. But I've added "on my computer" just in case it wasn't clear. I can't help with some similarly named mobile app. I don't really use a phone. $\endgroup$
    – James K
    Commented Nov 27, 2021 at 22:50
  • $\begingroup$ Ok thx I’ll try that $\endgroup$ Commented Nov 27, 2021 at 22:58
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    $\begingroup$ Got it working! "Magnitude" seems to mean "Apparent Magnitude" since Absolute Magnitude is listed separately. The figures I got was: Uranus - Saturn = +2.77 (2027). Uranus - Jupiter = -0.02 (2021). What was striking was that both Venus (+1.32/49) and the earth (+2.44/59) were brighter than Saturn when viewed from Uranus. Mercury's apparent magnitude was +3.41 (2067). And the dimmest planet - Mars was +5.61 (2033) $\endgroup$ Commented Nov 28, 2021 at 6:04
  • $\begingroup$ I don’t understand why my latest Stellarium search came up with a different figure than half a year ago? I did exactly the same thing, I think. Stellarium may not be functioning properly. It is also strange that my two figures, the old and new, differed from yours. I am just wondering if you would get the same figure if you carried out the exercise today? Check out the update in my answer. $\endgroup$ Commented Jan 31, 2023 at 11:22
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According to James K suggestion I downloaded the astronomical program “Stellarium” unto my desktop. Fiddled around with the different settings and got it working!

"Magnitude" seems to mean "Apparent Magnitude" since Absolute Magnitude is listed separately. The figures I got was: Uranus - Saturn = +2.77 (2027). Uranus - Jupiter = -0.02 (2021). What was striking was that both Venus (+1.32/49) and the Earth (+2.44/59) were brighter than Saturn when viewed from Uranus. Mercury's apparent magnitude was +3.41 (2067). And the dimmest planet - Mars was +5.61 (2033).

Thus, according to the excellent astronomical program “Stellarium” Jupiter’s apparent magnitude when watched from Uranus at its most favourable elongation in recent times (2021) was -0.02. And was then just a tad dimmer than the third brightest star in our night sky, Arcturus (-0.04).

Update 1: Strange is that today 30 January 2023 when I opened up Stellarium and went over the stats I got a slightly different figure than when I did the exercise in June 2022. Today the brightest apparent magnitude of Jupiter when watched from Uranus was not in 2021 but in January 2052. Namely at an apparent magnitude of -0.96. This is a big difference to the earlier figure of -0.02 in Dec 2021. By the way when I checked the brightest apparent magnitude of 2021 I found it to be -0.28, not -0.02. I wonder what is going on here?

Update 2: Today 22 September 2023 the figure for the brightest future apparent magnitude of Jupiter as going to be seen from Uranus is according to Stellarium -0.93, which it predicts will happen in 2037, 2051 and in 2120. Strange, different data again.

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