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Jupiter and magnification?

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#1 KBHornblower

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Posted 13 October 2020 - 08:19 PM

More than once while browsing Cloudy Nights I have seen assertions that Jupiter does not take high magnification as well as Mars or Saturn.  I cannot see either in theory or in my personal experience why this should be so.  I would expect additional magnification of arcsecond-scale detail on any visually small object to become "empty" on any of the bright planets at about the same value.  In moments of good seeing I see more small detail on Jupiter than on Saturn or Mars, which appear to me to have lower contrast except for Cassini's division.  Any comments are most welcome.



#2 areyoukiddingme

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Posted 13 October 2020 - 08:37 PM

Jupiter has lots of tiny, changing details that are comparatively low contrast. In my experience once I start going beyond about 250x in my 12.5" scope, I find I don't see any more detail. I might like the image scale better if it's a nice steady night, but I don't see more.

 

Whereas Saturn and Mars have comparatively large features--Cassini division, and subtle but large bands. Mar's has the ice caps, and regions with variances in shading that are comparatively homogenous. It also has smaller features that can be found (they are difficult) like Olympus Mons, but then it's usual that people report spotting it because it has a cloud around the top. Again a high contrast feature.

 

So it seems to be about finding an optimal magnification for relatively large but low contrast features, and my guess is that is because we are closer to a medium-high power that is where the eye gets maximal resolution of those Jupiter features.

 

But once you are talking about sharper contrasts, then the eye/brain can extract the information from higher magnifications.


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#3 TOMDEY

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Posted 13 October 2020 - 08:54 PM

Thanks for bringing this up! I have a theory on what's driving it... but will wait to see what others have to say, then I'll chime in.    Tom



#4 areyoukiddingme

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Posted 13 October 2020 - 09:04 PM

Hah, well my theory is not it!



#5 chubster4

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Posted 13 October 2020 - 09:40 PM

Maybe because Jupiter is brighter, your pupil stops down a bit more than when viewing dimmer planets. If it becomes smaller than the exit pupil, you'll effectively be losing some of your aperture, hence resolution.   


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#6 Ittaku

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Posted 13 October 2020 - 10:43 PM

Caveat: I'm not an experienced observer, but I've not found that at all. What I find is that it is much more revealing of what the true seeing quality is. I need excellent seeing to use the higher magnifications, but on the rare occasions seeing is excellent, I've been happily observing it at up to 450x and getting more out of it. When seeing is average, it's much more rewarding with 200-250x. Perhaps the relative lack of fine detail in other planets means that pushing the magnification isn't obviously detrimental but larger image is.



#7 KBHornblower

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Posted 14 October 2020 - 12:06 AM

Maybe because Jupiter is brighter, your pupil stops down a bit more than when viewing dimmer planets. If it becomes smaller than the exit pupil, you'll effectively be losing some of your aperture, hence resolution.   

No way.  At the magnification in question, 150x and up with a 6" scope, the exit pupil is less than 1/3 the diameter of my daylight pupil, not to mention my partially dilated night pupil.


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#8 chubster4

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Posted 14 October 2020 - 06:07 AM

No way.  At the magnification in question, 150x and up with a 6" scope, the exit pupil is less than 1/3 the diameter of my daylight pupil, not to mention my partially dilated night pupil.

 

 Maybe with a 20" scope and a larger exit pupil? lol.gif

I admit my idea's a stretch, but it's all my brain cell could come up with! Like you, I haven't personally experienced this effect. 



#9 Redbetter

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Posted 14 October 2020 - 09:39 AM

I have never understood the claims that Jupiter doesn't take magnification like Saturn and Mars.  I wonder if they are looking at different planets than I do.  Obviously they don't see them the same way as I do, but I am pretty sure the same physics apply.  

 

The weird thing is that everything about the claim points in different directions when one tries to consider why Jupiter is different to them.  Highest to lowest surface brightness is Mars, Jupiter, Saturn.  Contrast from high to low is probably Mars, Jupiter, Saturn as well.  Apparent size (resolution size) for planetary disk detail is Jupiter, then Mars or Saturn depending on where Mars is in its opposition sequence.  Of the three, Saturn probably has the least available detail and contrast at any magnification/angular resolution. 

 

My conclusion is that Saturn is primarily over-magnified for magnification's sake.  Since it is dimmer and of lower contrast, the flaws in the resultant rendering are less apparent to some or easier to overlook.  

 

I find that at similar elevations in the sky, seeing (or less frequently aperture) imposes the same effective limits for maximizing detail...oh, and this includes the Moon as well.



#10 E_Look

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Posted 18 October 2020 - 06:04 PM

I have, but rarely been able to magnify Jupiter and Saturn to powers over 250x in my 8" Newt.  The rarity is due to generally unfavorable seeing.  On those very rare nights of still air here, both planets can be magnified quite a bit.  And since Jupiter has the GRS, its notch, and "serrated" nature of the belts, when the air is relatively still, there is something to focus on.  On many nights though, each is a bit like a, as a space pirate said to his friend, "fuzzball".  Saturn is somewhat better as someone here said, because of the ansae, Cassini division, shadowing from the ring or moons.  But the surface features, like banding, are hard to focus on with your eye even if you have mechanically achieved optimal focus (like focusing one of the moons).  Last night, Jupiter was a bit awful, only the north and south equatorial bands were visible at all (along with the Galilean moons).  And of course Saturn was a bit better... mainly because of the rings and its features, the crepe ring seemed to tease my eyes with their ethereal presence, and looking for Dione and Rhea was fun; I didn't even try (too hard at all) to look for Tethys, and forget about Mimas or Enceladus; I can see them only when sky conditions are super (and more likely, when the rings are more edge-on).



#11 phillip

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Posted 18 October 2020 - 06:29 PM

Perhaps it's simply as previously noted, Jupiter has the larger size. 

 

Regardless enjoyed lots of ranges of powers on Jupiter, usually limits are certainly sky conditions. 

 

My sweet spot for average sky ranges just over 170x for majority of sky. 

 

200x abit frequent, above takes improved sky.

 

Clear Sky

 

XT10

 

Pentax 7mm, the frequent Winner! 



#12 CrazyPanda

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Posted 18 October 2020 - 08:36 PM

More than once while browsing Cloudy Nights I have seen assertions that Jupiter does not take high magnification as well as Mars or Saturn.  I cannot see either in theory or in my personal experience why this should be so.  I would expect additional magnification of arcsecond-scale detail on any visually small object to become "empty" on any of the bright planets at about the same value.  In moments of good seeing I see more small detail on Jupiter than on Saturn or Mars, which appear to me to have lower contrast except for Cassini's division.  Any comments are most welcome.

Yeah not sure where that assertion came from. I've had moments of steady enough seeing to observe both Mars and Jupiter at 400-500x in 12" and 15" scopes and there was one night in particular Jupiter would have kept slurping up magnification if it was available. I definitely reached the limit of my telescope long before the limit of what Jupiter would have had to offer.

 

Jupiter is by far the most visually dense planet in the solar system. The amount of stuff going on in its clouds really begs for steady skies and big apertures.


Edited by CrazyPanda, 18 October 2020 - 08:38 PM.

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#13 rehling

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Posted 20 October 2020 - 12:23 AM

Saturn certainly has less contrast on its disk than Jupiter, but the rings are much sharper and, obviously, contrasted from the black of space, than the details on Jupiter. The details on Saturn itself are basically just planetwide bands that have a smooth and "predictable" edge so there isn't much to see, but what is there to see is not as challenging.

 

It's interesting to see Jupiter when the shadow of a moon is on it, because those are very sharp compared to the other details.

 

I notice a significant downgrade in contrast when I magnify Jupiter more. With my 9.25" it is very nice and contrasty around 250x, but it loses a lot at 500x. The GRS is probably an exception… the color contrast there makes it still pop out at ~500x.


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#14 GeneT

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Posted 25 October 2020 - 05:58 PM

Jupiter takes magnification very well. Seeing, quality of optics, and size of the optics objectives play major roles on your question. I got great views of Jupiter from both 8 inch SCT and regular reflectors. My 4 inch reflector gave it a good try, but compared to the 8 inchers, there was no comparison. I owned a both a 20 and 18 incher Dob, and I was not impressed with my views of Jupiter when compared to my 12.5 inch Portaball. I find a 12 incher to be a nice size for planetary viewing. Of course, a 20 incher will outperform a 12, but good seeing is a factor, as is the quality of the optics. One reason I sold my 18 inch Obsession Ultra Compact was that I had to really look hard to see any more detail with it over my 12 inch Portaball.  


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#15 nibiru711

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Posted 25 October 2020 - 11:54 PM

The biggest problem with juipter most of the time is too much glare in bigger scopes. I t wouldn't glare as much here at the house as does out here in the mountains with no lights you wouldn't think that would be so but I find that a little light pollution isn't all bad for juipter.

 

    It would be nice to have Pentax eyepieces if you can afford them or lanathnum or delos or naglers. Orion sells a lanthanum zoom(it seems well rated) for about 200 dollars and lanthanum is suppose to help with glare but I haven't had premium zoom so I can't tell from experience.



#16 Abhat

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Posted 26 October 2020 - 09:47 AM

Where I live I rarely go above 150X. Maybe 200X on a very lucky day. Bad seeing and low on horizon makes Jupiter a difficult target. I occasionally see many astronomers quoting numbers like 300X-400X. I have never been able to do that. They must be living in areas where Jupiter is high in the sky and seeing is top notch.


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#17 REC

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Posted 26 October 2020 - 12:45 PM

Where I live I rarely go above 150X. Maybe 200X on a very lucky day. Bad seeing and low on horizon makes Jupiter a difficult target. I occasionally see many astronomers quoting numbers like 300X-400X. I have never been able to do that. They must be living in areas where Jupiter is high in the sky and seeing is top notch.

Yeah, 150x seems to be the best I can get in all my scopes where I live. Most nights we have a 3/5, but once in a while we get a 4/5 and I can go up to 185x. Never been over 200x on jupiter, but sure would as I have read that 200x ect is the sweet spot for jove. Saturn van take a little more magnification, but once Cassini goes, then I know it's too high. That's what make a zoom eyepiece so helpful. You can zoom in the the best spot or back off some if you need to.


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#18 GeneT

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Posted 26 October 2020 - 01:28 PM

Where I live I rarely go above 150X. Maybe 200X on a very lucky day. Bad seeing and low on horizon makes Jupiter a difficult target. I occasionally see many astronomers quoting numbers like 300X-400X. I have never been able to do that. They must be living in areas where Jupiter is high in the sky and seeing is top notch.

Jupiter does well in the magnification range of 100X to 300X. When seeing and optics are both excellent, you can crank up more power, however there is a point where additional detail will not be observed with additional magnification. 



#19 Cpk133

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Posted 26 October 2020 - 05:51 PM

Jupiter is better at any power with a binoviewer.  I have a hard time making out the little white ovals in the STR without at least 230X mono-view.  High contrast features are good at high power (shadow transits, GRS, GRS turbulence or hollow, dark festoon bases).  Wispy low contrast stuff is best at lower magnification where brightness is preserved.  Let's face it, you need to run the full gamut of power to get the most out of good seeing.  Saturn, I prefer at much higher powers.  I find that the polar darkening / banding is much easier to see around 500X.  The high contrast of the rings hold up under lots of power.  High contrast features like the sliver of the globe's shadow cutting across a minute slice of the ring is best at high power.  Oddly, i prefer mono-view on saturn at high power over bino,  Mediocre seeing makes the rings play tricks in the bino's.


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#20 Sheol

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Posted 27 October 2020 - 06:22 PM

      Maybe some are speaking of that somewhat softer edge to Jupiter's disk? I've seen it brought up before, that could make someone doubt their focus, I suppose. But as all have said, the planet has so many things going on all the time... 

 

 

   Clear Skies,

    Matt.



#21 E_Look

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Posted 27 October 2020 - 09:41 PM

In previous years, the GRS was something to focus on.  I haven't looked for it lately though; don't even know what it looks like this year.



#22 doolsduck

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Posted 27 October 2020 - 10:19 PM

Saturn certainly has less contrast on its disk than Jupiter, but the rings are much sharper and, obviously, contrasted from the black of space, than the details on Jupiter. The details on Saturn itself are basically just planetwide bands that have a smooth and "predictable" edge so there isn't much to see, but what is there to see is not as challenging.

It's interesting to see Jupiter when the shadow of a moon is on it, because those are very sharp compared to the other details.

I notice a significant downgrade in contrast when I magnify Jupiter more. With my 9.25" it is very nice and contrasty around 250x, but it loses a lot at 500x. The GRS is probably an exception… the color contrast there makes it still pop out at ~500x.


This is what I see too though I have absolutely no idea of any basis in fact. I can see contrasty detail on Mars at 330x in my 14” Newt, but not low contrast details, I can see really narrow rilles on the Moon when they too are contrasty. I can see a sharp Cassini division and sharp rings on Saturn at 339x times too, but I can never see any low contrast details on the planetary body except whatever that colour band is. And if on a night of good seeing I can swing straight from a great view of Saturn at 330x to Jupiter and the low contrast details aren’t easily made out, but the GRS is and any moon shadow is likewise sharp. Do edges come into play?

#23 Sheol

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Posted 29 October 2020 - 06:28 PM

              I haven't given the King of Planets any love this year, I'm afraid. But when I was last very active in the Hobby back in 2013-14, the GRS was certainly visible. But it was not red. More like pastel pink. lol.gif

              I know it changes colors & even size, so I do not know if its visible at all this year. Anyone who has seen it?

 

            Clear Skies,

               Matt.



#24 Asbytec

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Posted 29 October 2020 - 06:58 PM

More than once while browsing Cloudy Nights I have seen assertions that Jupiter does not take high magnification as well as Mars or Saturn. I cannot see either in theory or in my personal experience why this should be so. I would expect additional magnification of arcsecond-scale detail on any visually small object to become "empty" on any of the bright planets at about the same value. In moments of good seeing I see more small detail on Jupiter than on Saturn or Mars, which appear to me to have lower contrast except for Cassini's division. Any comments are most welcome.

In my experience, the reason has less to do with resolution and more to do with image surface brightness, bright low contrast detail, and observer acuity (and seeing, etc.) At smaller exit pupils, Jupiter's image dims by a couple of magnitudes, all planets do. But because of the plethora of bright low contrast detail on Jove, but not very much on Saturn, the exit pupil matters. As the image dims, we tend to loose bright low contrast detail. It's not the scope's fault, that detail is still in the afocal image. It does not go away. It's just more difficult for us to see as our eye moves away from high resolution photopic vision.

In terms of resolution of two points, magnification /can/ become empty at some point. That may not always be true, however, for larger planetary features (and small bright planetary nebulae). Or even bright double stars where high magnification can help. Planetary detail is not so much dependent on resolution in terms of Rayleigh or Dawes, which don't apply to extended object detail, rather it depends on contrast and image scale on our eye. Bright high contrast detail, like Mars and Saturn's rings, can take higher magnification and survive image dimming on our eye. (Mars has low contrast detail, too, as does Saturn).

Edit: I'm always much higher magnification on Mars. Some of that is due to its small size, but the bright higher contrast image can take it. Rather, my eye can take it. I tend to over magnify Saturn, too, but mostly because of its rings. The globe is more difficult anyway you slice it. Jupiter is normally the benchmark.

"I have never understood the claims that Jupiter doesn't take magnification like Saturn and Mars."

Red, I've never understood claims of ludicrous magnification on Jove. I've been that high and don't see much at all, just a few main belts and the limb. I gotta drop down and brighten the image to regain detail. Jove's sweet spot for me in an 8" aperture is 0.6mm exit pupil or a bit over 300x. Saturn's globe about the same (or higher). Mars is closer to 400x. Saturn's rings as high as 600x. Each as seeing permits.

Edited by Asbytec, 29 October 2020 - 07:18 PM.

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#25 BillP

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Posted 01 November 2020 - 08:45 AM

Jupiter has lots of tiny, changing details that are comparatively low contrast. In my experience once I start going beyond about 250x in my 12.5" scope, I find I don't see any more detail. I might like the image scale better if it's a nice steady night, but I don't see more.

 

Whereas Saturn and Mars have comparatively large features--Cassini division, and subtle but large bands. Mar's has the ice caps, and regions with variances in shading that are comparatively homogenous. It also has smaller features that can be found (they are difficult) like Olympus Mons, but then it's usual that people report spotting it because it has a cloud around the top. Again a high contrast feature.

 

So it seems to be about finding an optimal magnification for relatively large but low contrast features, and my guess is that is because we are closer to a medium-high power that is where the eye gets maximal resolution of those Jupiter features. ...

 

I think this nails it fairly well.  But still, some will not necessarily see Jupiter behave this way.  Why?  IME it is because different observers focus on different aspects of the planet.  So when one's primary focus is on the major high contrast features then all of a sudden the planet can take lots of magnification.  But for those whose focus is more on the subtle stuff, then the planet cannot take as much magnification, as it should not be able to given the physics of the situation.  So it really depends on where one's focus is because where their focus is, is where their perception system then either accentuates or filters out the information their eye is receiving.  You see this phenomena in action a lot when people post equipment comparison reports that often say they did not see some feature with one eyepiece but did with the other, then when they went back to check the other eyepiece it was there after all.  So don't be fooled into thinking that one's perception of reality through the use of their senses is actually reality.  It is not.  Instead it is the reality as seen through the "lens" of their perception which has been altered/changed/modified by their unique genetic predispositions, past experiences, prior knowledge, emotions, preconceived notions, self-interest, and cognitive distortions.  As such it is not an accurate representation of what the reality truly is.  All part of being human!
 


Edited by BillP, 01 November 2020 - 08:48 AM.

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