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Jupiter and magnification

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#1 GeorgiBG

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Posted 06 August 2020 - 02:31 AM

The clouds and the wind are finally gone so naturally I pointed my refractor to the skies again. This time I went for 28x magnification and pointed the scope towards Jupiter at about 23 degrees above the horizon. To my huge surprise I managed to see clear orange like colors on the 2 equatorial bands and pastel white colors elsewhere. I quickly switched to 70x magnification and the whole planet though bigger was a mix between white and brown pastel colors. Why? On the other hand, Saturn is too small with 28x magnification and literally perfect with 70x magnification.

#2 james7ca

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Posted 06 August 2020 - 02:49 AM

Well, the lower your magnification the more the colors will mix which could change the apparent tint of the cloud bands. Also, as you increase your magnification the image of Jupiter will get dimmer and at some point you may begin to lose the ability to actually see color (basically under very dim illumination or when looking at a very faint object you will lose much of your ability to see color). That said, 70X isn't that high of a magnification even for a 70mm scope (should produce about a 1mm exit pupil), so I don't think that would be dim enough to notably "rob" you of your color vision.

 

That said, you've got a complex mix of issues here, changes in contrast, changes in apparent sharpness, changes with the color tint added by the eyepieces, with perhaps some dimming of your color perception.


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#3 sg6

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Posted 06 August 2020 - 02:56 AM

I guess that the brightness of Jupiter that the bands and detail begin to merge, the scope reads as a 70mm f/10 achro. Staurn has in a way less detail - you likely had a planet of about 1 overall color and a ring around it. Simply a ball and a ring is in a way not a lot of detail. Where a GRS and what amounts to 4 or 5 at least bands is. So some is you interpretation.

 

I say 4 or 5 bands as you have to have had a white bit, a band (1), another white bit, another band (2), then a final white bit. counting the indistinct white bits as bands you were looking at in effect 5 bands.

 

Have seen Jupiter at about the same as you and will agree looked supurb. Will say best Saturn was at 125x but in a 1000mm refractor (8mm eyepiece). Did try Saturn last year in a 102/600 refractor and basically garbage - too much CA but a ball and rings.

 

Scopes, refractors, have one little mentioned aspect - depth of focus. An achro tends to have a "larger" DoF and makes sitting at the right place easy but the focus is never 100% sharp. With higher magnifications you experience the poor aspect of this more - the not so sharp bit. That is why people say an ED/apo snaps to focus, they have a small depth of focus - you have to get it just right, but results are good.

 

Might suggest better eyepieces - everyone does. Half guess yours are Huygens or Ramsdens. A reasonable plossl might help deliver an improved image. Something for around 60 on Jupiter maybe, which would be 12mm (ish). Saturn really means trying an 8mm.

 

Any chance of you borrowing a plossl or two? To try before committing to spending money.


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#4 GeorgiBG

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Posted 06 August 2020 - 04:39 AM

Thanks for the answers! My eyepieces are rebranded Kellners with a rubber band for the eyes. I will invest a few bucks for SP ones at about 7.5mm and something between 15-20mm range. Saturn is not solid color though, it's a shades of yellow without visible details, the Cassini division is barely visible but noticeable in very dark skies together with Titan and Rhea, sometimes Iapetus.

It's good to know that lower magnification doesn't mean less visible details. :)
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#5 Redbetter

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Posted 06 August 2020 - 04:55 AM

I would expect that scope to do well at around 100x for planets, a 7mm eyepiece.  I wouldn't suggest starting much shorter in focal length initially with this aperture and ratio of achro, with the planets so low for you.  I suspect 100x will be near a sweet spot.  Plossls below 10mm have very short eye relief, with Orthos only slightly better in the same focal lengths, so something with a bit more eye relief (e.g. 10mm of eye relief or more) is recommended.    I am not well versed on the eyepiece options in this range in Europe.  I will say that an old 7mm Type I Nagler is a great eyepiece for this sort of thing, if you come across one--they were pricey back in the day, but are relative bargains now.

 

I was using ~22x briefly on Jupiter tonight in the backyard with an AT72ED.  While I only have mild levels of astigmatism, the planet is quite small and overly bright at 3.3mm exit pupil.  This really limits the detail for my eye.  An eagle-eyed younger observer might see more with such a wide exit pupil, but the view has less glare for me at an exit pupil of 1mm or below.  The level of detail is several orders of magnitude greater at 100x than it is in the 20's.  Color impressions interest me less than detail.  


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#6 Tony Flanders

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Posted 06 August 2020 - 06:10 AM

Thanks for the answers! My eyepieces are rebranded Kellners with a rubber band for the eyes. I will invest a few bucks for SP ones at about 7.5mm and something between 15-20mm range. Saturn is not solid color though, it's a shades of yellow without visible details, the Cassini division is barely visible but noticeable in very dark skies together with Titan and Rhea, sometimes Iapetus.

It's good to know that lower magnification doesn't mean less visible details. smile.gif

When the atmosphere is sufficiently steady and the planets sufficiently high, lower magnification does indeed mean less detail. But when the seeing is mushy, there's no point in over-magnifying your target. In good conditions, in a 70-mm scope, I would expect the best planetary views at 70X to 100X.

 

If you can see the Cassini Division through a 70-mm refractor, you're doing very well indeed; count your blessings. I doubt that different eyepieces will improve the view significantly; there's nothing at all wrong with Kellners.


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#7 gnowellsct

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Posted 06 August 2020 - 07:29 AM

I will take this question as specifically about color. The amount of color your telescope gathers on Jupiter for example increases with aperture but it decreases with magnification. Even stars may lose their brilliant intensity and color as the magnification increases. They are point sources but they really aren't, they are seeing discs with a physical size as they come into your eyeball and as you start looking at dimmer stars their color intensity diminishes with magnification.

In any event it was during a lunar eclipse that I got a very good demonstration of the inverse relationship between magnification and color. In the small telescopes that were at this event the moon was at magnifications of anywhere from 16x to 30x and there was a nice blood red saturated effect. In my 9.25 The moon was a soft pastel of grays and blues with a hint of red but no bright red saturated effect. And in fact at this event the binoculars were showing the reddest moon of all except that the naked eye view was redder still.

Basically I think what's going on is that as the image is concentrated in a smaller area in your eye the colors are more intense.

But aperture also has its effect. Jupiter is a riot of color at 100x in a c14 but the colors are much more subdued in a 92 mm refractor at 100x.

The phrase " dimming out " refers to the well-known dimming of images as we push the magnification of a telescope towards 2x per millimeter of aperture and beyond. If you are looking during the daytime at a distant plant for example at extremely high magnifications the brilliant greens that you see at low magnification become more subdued and the whole image becomes darker.

This lunar eclipse taught me that there are basically two curves working in the transmission of color. One is the loss of color intensity as magnification is increased. The other is that there is an increase of color to look at in a larger instrument but that if you have a long focal length instrument such as a c9.25 with an inherently high magnification you might, on an extended object such as the Moon, lose color intensity to the magnification at a rate that is faster than what you gain through the larger aperture.

if you want to have a great lunar eclipse watch it through a small refractor. The range of colors on display is spectacular and you're not really pursuing fine lunar detail. And then the stars come out around the moon which usually annihilates all the stars. It is a stunning effect.

I think that someone with a serious optical background could graph the increase in color intensity with aperture against the decrease in color intensity with magnification and that it would be an interesting chart to have.

Small refractors rule the schools in delivering color on a lunar eclipse. But the big scopes at low powers will blow them away in terms of Jovian color. but that does not mean that the colors in a refractor are at zero level.

As a side point there is considerable variation from person to person in the ability to detect color. In many cases, mostly with men, there is some degree of red green colorblindness. But even among people who have not been diagnosed there are variations in color sensitivity.

Edited by gnowellsct, 06 August 2020 - 07:30 AM.

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#8 rhetfield

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Posted 06 August 2020 - 08:11 AM

I will take this question as specifically about color. The amount of color your telescope gathers on Jupiter for example increases with aperture but it decreases with magnification. Even stars may lose their brilliant intensity and color as the magnification increases. They are point sources but they really aren't, they are seeing discs with a physical size as they come into your eyeball and as you start looking at dimmer stars their color intensity diminishes with magnification.

In any event it was during a lunar eclipse that I got a very good demonstration of the inverse relationship between magnification and color. In the small telescopes that were at this event the moon was at magnifications of anywhere from 16x to 30x and there was a nice blood red saturated effect. In my 9.25 The moon was a soft pastel of grays and blues with a hint of red but no bright red saturated effect. And in fact at this event the binoculars were showing the reddest moon of all except that the naked eye view was redder still.

Basically I think what's going on is that as the image is concentrated in a smaller area in your eye the colors are more intense.

But aperture also has its effect. Jupiter is a riot of color at 100x in a c14 but the colors are much more subdued in a 92 mm refractor at 100x.

The phrase " dimming out " refers to the well-known dimming of images as we push the magnification of a telescope towards 2x per millimeter of aperture and beyond. If you are looking during the daytime at a distant plant for example at extremely high magnifications the brilliant greens that you see at low magnification become more subdued and the whole image becomes darker.

This lunar eclipse taught me that there are basically two curves working in the transmission of color. One is the loss of color intensity as magnification is increased. The other is that there is an increase of color to look at in a larger instrument but that if you have a long focal length instrument such as a c9.25 with an inherently high magnification you might, on an extended object such as the Moon, lose color intensity to the magnification at a rate that is faster than what you gain through the larger aperture.

if you want to have a great lunar eclipse watch it through a small refractor. The range of colors on display is spectacular and you're not really pursuing fine lunar detail. And then the stars come out around the moon which usually annihilates all the stars. It is a stunning effect.

I think that someone with a serious optical background could graph the increase in color intensity with aperture against the decrease in color intensity with magnification and that it would be an interesting chart to have.

Small refractors rule the schools in delivering color on a lunar eclipse. But the big scopes at low powers will blow them away in terms of Jovian color. but that does not mean that the colors in a refractor are at zero level.

As a side point there is considerable variation from person to person in the ability to detect color. In many cases, mostly with men, there is some degree of red green colorblindness. But even among people who have not been diagnosed there are variations in color sensitivity.

Remember that as color gets "brighter", it becomes lighter.  Light red is pink.  Light pink is "warm white".  Similarly, dark red becomes burgundy and eventually black.  concentrating color with magnification will wash it out until it is off-white.


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#9 Jethro7

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Posted 06 August 2020 - 08:14 AM

Hello Georgi,

One thing, Jupiter and Saturn are fairly low on your Horizon. As you increase power you also magnifying atmospheric distortions and being low on the Horizon  you are viewing Jupiter and Saturn through more atmosphere.complicated by other things like lens quality. Scope not in temperature equilibrium.as power increases your views get darker. I think most of this is the Planets position in your Sky. I was out last night doing the same but Jupiter and Saturn are much higher in my skies. And I had good seeing conditions. The best views of Jupiter with My AT102 ED were at 71.4X to 102X I could clearly see the big red spot as it was sliding around and out of view as with the the cloud banding. The nice thing at this power range, is the Galileans were nicely lined up on one side of Jupiter, the and all were in the eyepiece.  What you are seeing in the eyepieces is normal. 

 

HAPPY SKIES AND KEEP LOOKING UP Jethro


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#10 gnowellsct

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Posted 06 August 2020 - 11:47 AM

When the atmosphere is sufficiently steady and the planets sufficiently high, lower magnification does indeed mean less detail. But when the seeing is mushy, there's no point in over-magnifying your target. In good conditions, in a 70-mm scope, I would expect the best planetary views at 70X to 100X.

 

If you can see the Cassini Division through a 70-mm refractor, you're doing very well indeed; count your blessings. I doubt that different eyepieces will improve the view significantly; there's nothing at all wrong with Kellners.

Well there's 70 mm like this and there's 70 mm like this so which one would be more likely to show Cassin's.  If you use the provided aperture mask you can see Cassini's with a 40mm aperture in the Vixen SD81s.

 

Thanks for the answers! My eyepieces are rebranded Kellners with a rubber band for the eyes. I will invest a few bucks for SP ones at about 7.5mm and something between 15-20mm range. Saturn is not solid color though, it's a shades of yellow without visible details, the Cassini division is barely visible but noticeable in very dark skies together with Titan and Rhea, sometimes Iapetus.

It's good to know that lower magnification doesn't mean less visible details. smile.gif

That's not entirely true.  There are certain objects which disappear altogether if the magnification goes too low (mostly deep sky).   And I find I don't get "all the detail" off Jupiter at 16x in a 92mm.   

 

But these are quibbles.  It is true that if one is seeing Cassini's one is doing better than a good many amateurs whose telescopes or local seeing impede their views.  And Kellners are good oculars. 

 

And a lot of good detail emerges at powers lower than the max.  Sometimes the only real reason to boost the magnification is to get the object to dim out.  Jupiter at 16x is a sock in the eye it is so bright. 

 

Greg N


Edited by gnowellsct, 06 August 2020 - 11:49 AM.

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#11 KBHornblower

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Posted 06 August 2020 - 12:52 PM

Let me remind everyone that changing the magnification does not change the spectrum of Jupiter or any part of it.  Everything on Jupiter is pastel, and any perceived differences in the vividness of the color at different magnifications are as a result of how our brains interpret what comes from the retina.


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#12 GeorgiBG

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Posted 06 August 2020 - 02:38 PM

Remember that as color gets "brighter", it becomes lighter.  Light red is pink.  Light pink is "warm white".  Similarly, dark red becomes burgundy and eventually black.  concentrating color with magnification will wash it out until it is off-white.

Your description pretty much summarizes the change of colors which I saw with this magnifications.smile.png



#13 james7ca

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Posted 07 August 2020 - 12:55 AM

Remember that as color gets "brighter", it becomes lighter.  Light red is pink.  Light pink is "warm white".  Similarly, dark red becomes burgundy and eventually black.  concentrating color with magnification will wash it out until it is off-white.

Your description pretty much summarizes the change of colors which I saw with this magnifications.smile.png

Except that I think rhetfield is saying that the colors will be lighter and more washed out as they become brighter (suggesting that lower magnifications will produce lighter and more washed out colors). So, wasn't that the opposite of what you saw?

 

In fact, that post seems to contain at least two contradictory statements, "brighter" changes "light red [to] pink" while "dark red" becomes "black." So, how could black be "brighter" than dark red? confused1.gif


Edited by james7ca, 07 August 2020 - 12:55 AM.


#14 GeorgiBG

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Posted 07 August 2020 - 03:20 AM

That's correct, James. In the case of Jupiter I got better colors with low magnification and less colors with high magnification. The opposite was true for Saturn - simple yellow color at low and shades of yellow and better contrast at high.

I'm in no way experienced enough to guess what is causing this effect on those planets. The only thing which is apparent are the magnitudes - Saturn is much more dim, while Jupiter is very bright right now.

#15 james7ca

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Posted 07 August 2020 - 03:58 AM

That's correct, James. In the case of Jupiter I got better colors with low magnification and less colors with high magnification. The opposite was true for Saturn - simple yellow color at low and shades of yellow and better contrast at high.

I'm in no way experienced enough to guess what is causing this effect on those planets. The only thing which is apparent are the magnitudes - Saturn is much more dim, while Jupiter is very bright right now.

But, that's kind of the opposite of what rhetfield seems to be saying (I think, his/her post has some confusing wording). rhetfield's statements seem to suggest that a brighter light source will have more "washed" out colors. Which is true when a light source get too bright. Think of brightly colored lights, the greater the brightness the less color they seem to have.

 

However, a lower magnification is going to produce a brighter image (and by rhetfield's post that means a more washed out color) . So, what was rhetfield actually trying to say and why did you agree when you said, "Your description pretty much summarizes the change of colors which I saw with this magnifications."?

 

In any case, note what I said in post #2, as objects become much dimmer it becomes harder to perceive color (with an emphasis on "much"). This is easy to confirm. Just sit in a room at night (with the lights on) and look at something that has bright, contrasting colors. Now turn off most or all of the lights and note that the object appears almost in grayscale. Under dim lighting (or when looking at a faint object) you see mainly luminance (brightness differences), not much in the way of color.

 

But, it makes little difference since I think what you were experiencing is mostly a difference in perception (meaning how your eyes detect and how your brain interprets what is being seen). Plus, because of the magnification changes you went from seeing less to more detail. So, it's kind of a mix of conditions.



#16 Tony Flanders

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Posted 07 August 2020 - 06:21 AM

Seeing color on the planets is a very complex question.

 

First of all, you certainly won't see any color at all if you over-magnify too much, in which case the planets become so dim that they barely stimulate color vision. Conversely, you probably won't see much color at very low magnifications, because color vision tends to wash out when the light source is very bright. Then there's the question of how many cone cells are stimulated -- I'm not sure how that plays out.

 

But most important, in my experience seeing color on Jupiter is largely a matter of contrast. Regardless of magnification, the colors are most vivid when the seeing is good, and largely disappear when the seeing is lousy. That's presumably because color perception is not a matter of what wavelengths are hitting your eye so much as contrast between two different regions within the image. A sheet of white paper looks white whether you see it in incandescent light, which is actually pretty deep red, or by sky light (in a shadow on a sunny day), which is quite blue. Likewise, if half the sheet is one color and the other half another color, you can get a pretty good guess at those colors across a huge range of different illuminations. It's the edge between the two that cues your eye to see different colors. In poor seeing the edges fade out, and so does color perception.

 

So one of the reasons that higher magnifications might reduce the perception of color on Jupiter is that it makes the edges fuzzier.


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#17 MaknMe

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Posted 07 August 2020 - 07:37 AM

Jupiter gets all the magnification the seeing will allow. If it is good, I use my highest power eyepiece (about 200x). If it isn’t as good, I use a low power eyepiece and a Barlow (about 150x). In my eyepiece, higher power equals better details and (it seems to my eyes) more vibrant colors.

At 50-75x I can see some color and 2 bands, but little detail.

Edited by MaknMe, 07 August 2020 - 07:39 AM.


#18 Redbetter

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Posted 07 August 2020 - 06:05 PM

But most important, in my experience seeing color on Jupiter is largely a matter of contrast. Regardless of magnification, the colors are most vivid when the seeing is good, and largely disappear when the seeing is lousy. That's presumably because color perception is not a matter of what wavelengths are hitting your eye so much as contrast between two different regions within the image. A sheet of white paper looks white whether you see it in incandescent light, which is actually pretty deep red, or by sky light (in a shadow on a sunny day), which is quite blue. 

Yep, seeing has a large impact on color perception and contrast.  The nights with the most vivid color contrast always seem to correlate with better seeing.  They also provide the best fine planetary detail. 

 

Even reasonable sized features like Red Spot Junior suffer from this.  It can be seen with small scopes in good seeing, but its color contrast is often so weak (since in recent years it has not been red) that it is seen mostly as an empty notch in poor/mediocre seeing.  The darker brow around it varies in hue and provides some defining contrast at times.  There is another somewhat salmon colored oval closer to the south polar region that is similar in size to the white ovals, but has only modest contrast.  It takes unusually good seeing (for here) to reveal it in a large scope.

 

The color and albedo contrast play out when trying to track moons in front of Jupiter's disk.  The particular moon, and which portion of the disk, limb, belt, zone, or region all contribute to visibility.  Better seeing means better color contrast.

 

And on an even lesser appreciated side, excellent seeing improves the contrast of DSO's as well as how deep one can go.  Dust lanes, arms, bars, knots, etc. are all enhanced by stable seeing.  The faintest/smallest galaxies go missing as seeing declines. 



#19 smasraum

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Posted 07 August 2020 - 07:27 PM

Jupiter gets all the magnification the seeing will allow. If it is good, I use my highest power eyepiece (about 200x). If it isn’t as good, I use a low power eyepiece and a Barlow (about 150x). In my eyepiece, higher power equals better details and (it seems to my eyes) more vibrant colors.

At 50-75x I can see some color and 2 bands, but little detail.

In my old 8" dob in light polluted skies, I was the same, how much mag will atmospheric conditions support.  I can't remember what my max possible mag was (based on EP that I owned) but I think it was 295-325x.  I was able to occasionally max out on Mars, Saturn and Jupiter without any problem and always saw color on all of them up to that mag.  I was usually able to get up to around 175-200x, and sometimes 250 or 300ish.  On Mars I saw the "red" surface with the dark color and even polar ice caps.  On jupiter, I saw bands including the "waves" between the bands and even the GRS (although, it looked white to me).  On Saturn, I saw alternating bands of color. 
 




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