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Viewing Saturn

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Old Thursday 11th July 2019, 21:15   #1
tenex
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Viewing Saturn

Why is it that ordinary binoculars (even 15x, I'm using SLC) will show Jupiter and its moons beautifully, but with Saturn there's only a vague sense of oblateness? So tiny an image won't show much detail, but at 15x I would expect the ring to seem quite narrow at least relative to the disc and perhaps even separated by a tiny gap. Are consumer binos just not that well corrected, or not optimized for infinity?
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Old Thursday 11th July 2019, 21:43   #2
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Hello,

simply too little magnification and therefore resolution!
With a 50mm. Telescope and at 25-30 magnification, the ring can be separated from the planet!
In addition, Saturn is about twice as far away as Jupiter.

Andreas
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Old Thursday 11th July 2019, 23:27   #3
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Andreas is correct, increased magnification is necessary to decipher the rings of Saturn. With the right atmospheric conditions 30X will do the job.

Andy W.
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Old Friday 12th July 2019, 00:58   #4
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What is the minimum binocular for the Gallilean moons?

Edmund
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Old Friday 12th July 2019, 03:44   #5
Chosun Juan
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Question

Quote:
Originally Posted by tenex View Post
Why is it that ordinary binoculars (even 15x, I'm using SLC) will show Jupiter and its moons beautifully, but with Saturn there's only a vague sense of oblateness? So tiny an image won't show much detail, but at 15x I would expect the ring to seem quite narrow at least relative to the disc and perhaps even separated by a tiny gap. Are consumer binos just not that well corrected, or not optimized for infinity?
I'm wondering if, or how well, a set of doublers would work with the 15x SLC ? (56mm A-K version? That's top glass, though I don't know how it compares in the measured resolution stakes. The ones I've looked through in the field seemed very clear). That would take the EP down from 3.7mm to 1.8mm. Obviously going to need a sturdy tripod either way.





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Old Friday 12th July 2019, 06:12   #6
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Quote:
Originally Posted by dries1 View Post
Andreas is correct, increased magnification is necessary to decipher the rings of Saturn. With the right atmospheric conditions 30X will do the job.

Andy W.
In good seeing conditions, and with a very good instrument, even 20x will clearly show the separation between the ring and the planet body. E.g., Oberwerk 20x65 or APM 20x70 ED have done the job for me. Whether 18x would also work (Nikon Astroluxe) I have not been able to determine yet, this would probably require exceptionally good conditions to try.
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Old Friday 12th July 2019, 08:17   #7
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Wow Canip, then you have very good eye's!

>Edmund<
Some Astro colleagues say that you can sometimes see Ganymede (the largest Jupiter's moon) even without aids!
For that you have to cover the Jupiter disc with your thumb because of the oversteer, but I have not succeeded yet.
Otherwise I have no problems with a 6x30 binoculars, certainly less is possible.

Andreas

Last edited by Conndomat : Friday 12th July 2019 at 08:19.
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Old Friday 12th July 2019, 16:46   #8
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The reason for the disparity of observations of Saturn and Jupiter is that casual observers are not planetary observers.

Both vary depending on the distance from Earth.
The rings of Saturn vary from edge on to fully open because of Saturn's 29 year orbit around the Sun.

Jupiter's equatorial diameter varies from 31 arcseconds to 46 arcseconds.
Currently Jupiter is 45" equatorial diameter, 42" polar diameter.
It is magnitude minus 2.6 almost the maximum.
Near conjunction it is magnitude minus 1.8.

Saturn's equatorial diameter varies from 15" to 18.5".
Currently Saturn's equatorial diameter is 18.4", polar diameter 16.9".
It is magnitude 0.1.
Saturn's brightness depends on the distance from Earth and the tilt of the rings.
Currently the tilt is 24 degrees.
The rings major axis is now 41.7" minor axis 17.2".
Currently Saturn is very low from England, better from the U.S. Declination minus 22 degrees.

So what does this mean?
Well, it will be seen better from the U.S. and further south.

I have often seen the gap between the globe and rings with a specially made Soviet 20x60 and also with my Canon 18x50 IS.
Just with the binocular braced gently against the double glazing and window frame, hand held. Through the glass.
Also the Nikon 10-22x50 at 22x, but terrible false colour.
The visibility of the gap depends mostly on how good a person's eyesight is.

I have seen Titan, Saturn's largest moon at elongation with quite small binoculars, when Saturn was high in the sky and Saturn near opposition. Magnitude 8.4. I have also seen it with a scope stopped to less than 20mm.
A Swarovski 95mm should show 5 Saturn moons in good conditions.

Children are the ones who normally see Jupiter's moons with unaided sight.
Paul Doherty could see several when middle aged.
The visibility of the moons depends on the distance from the planet. They need to be at elongation.
2 or 3 moons can combine to be rather easily seen as one combined moon.

I have never seen Jupiter's moons without optical aid.

However, Jupiter's moons have been seen by quite a few observers without optical aid.
Next in difficulty is Venus crescent without optical aid.
Lastly, Saturn's elliptical rings shape has been seen by those with fine eyesight, without optical aid.

I expect young aboriginal Australians to see all three for the last thousands of years.

Regards,
B.

Last edited by Binastro : Friday 12th July 2019 at 17:30.
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Old Friday 12th July 2019, 17:49   #9
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Quote:
Originally Posted by eronald View Post
What is the minimum binocular for the Gallilean moons?
I can see them easily with any binocular at all, and think most people can. (Sometimes fewer than 4 are visible.) I think it's the proximity of the rings to Saturn that creates a need for greater resolution.

Quote:
Originally Posted by Chosun Juan View Post
I'm wondering if, or how well, a set of doublers would work with the 15x SLC ? (56mm A-K version? That's top glass, though I don't know how it compares in the measured resolution stakes. The ones I've looked through in the field seemed very clear). That would take the EP down from 3.7mm to 1.8mm. Obviously going to need a sturdy tripod either way.
Thanks for that suggestion! I believe Henry Link has reported that the SLC 56 does very well with a doubler, though that may have been the 10x SLC rather than 15x, and perhaps not a pair of doublers (does that introduce problems?).
Edit: the Swaro doubler seems to have been discontinued! Does anyone know about this?

Quote:
Originally Posted by Binastro View Post
I have often seen the gap between the globe and rings with a specially made Soviet 20x60 and also with my Canon 18x50 IS.
Just with the binocular braced gently against the double glazing and window frame, hand held. Through the glass.
Also the Nikon 10-22x50 at 22x, but terrible false colour.
The visibility of the gap depends mostly on how good a person's eyesight is.
I have seen Titan, Saturn's largest moon at elongation with quite small binoculars, when Saturn was high in the sky and Saturn near opposition.
Saturn is currently at opposition and the rings are favorably inclined, so there's some buzz about viewing it. But I've even tried with eyeglasses (since I have mild astigmatism) and that doesn't seem to help, at 15x I just can't distinguish the rings. Others claim to be able to do so at 20 or more commonly 25x, and of course it takes more to see any detail in the rings. I don't have such magnification available. I haven't tried to identify Titan (distinguish it from a background star over a period of time), and should remember to.

Last edited by tenex : Friday 12th July 2019 at 17:59.
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Old Friday 12th July 2019, 18:57   #10
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Hi Tenex,
I would suggest two possibilities that may help.

Put 45mm masks in front of the 15x56 objectives made of black cardboard.
I.e. use the binocular as a 15x45.

If possible tilt the binocular and your head to be more in line with your astigmatism. Without strain of course.
It may even be better using one side of the binocular with tilted head.

If you have glasses for distance vision that magnify slightly, this will increase the magnification to 16x maybe.

If you have a 4x monocular or binocular, then placing it between the 15x56 and your eyes will almost certainly show the ring gap.
The binocular on a tripod.

I used the Celestron 20x80 and a 7x binocular in tandem for excellent results. 140x.

I nearly always saw the ring gap with the Soviet 20x60 with the rings open.
It was more difficult with the Canon 18x50 IS.
I did not succeed with a 15x50 Soviet binocular.

In the last five years my eyesight has worsened and I would not expect to see the gap with the 18x50 IS.
However, Saturn is so low here that it is completely hidden by houses and I have not seen it yet this year.
I have seen Jupiter in a gap between houses at 3 a.m.

Regards,
B.

Last edited by Binastro : Friday 12th July 2019 at 19:01.
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Old Saturday 13th July 2019, 12:42   #11
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It may need 20/12 eyesight to see the gap between Saturn's globe and the ring near the extremity of the long axis, with a 15x binocular at present.
With a 24 degree ring tilt it will be more difficult than with a 27 degree tilt.

When I look for the gap between globe and ring, for some reason I look for the gap on the right side, not the left. This may be easier for me to see for some reason.

In fact, seeing the ring gap only means that one is seeing a double or triple planet.
With early telescopes Saturn was seen as a triple planet, and that is what we see with say 20x binoculars.
We only assume that we see the rings when we don't actually see them.

I need 30x to see the true nature of the rings, but this is again based on my knowledge that Saturn has rings.

It was not until 1655 that the Dutch astronomer, inventor, physicist and mathematician Huygens discovered the rings with his own made telescope of 50x magnification. He also discovered Titan with this telescope.
It probably needs 50x to actually discover the rings.

Regards,
B.
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Old Saturday 13th July 2019, 14:18   #12
Chosun Juan
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.....I expect young aboriginal Australians to see all three for the last thousands of years.
Bin,

I've been looking into the astronomical origins of the "Dark Emu" since I'm currently discussing a book by the same name by elder Bruce Pascoe. Apparently the dark streak in the Milky Way being caused by gas clouds which take the shape of an elongated Emu (like it is swimming).

I'm also researching the Southern Cross for other reasons, and it appears near the emu's head.

The sad thing is that in my relatively sparsely populated suburbia on the edge of the city I can't see Milky Way or Dark Emu ......
The Southern Cross is easy to distinguish.

From photos I have seen of the Milky Way /Dark Emu from remote outback sites, there are so many stars visible (millions?) that the Southern Cross is very difficult to separate from the blanket of stars. Conversely the Dark Emu sticks out beautifully.

Indigenous people's all over the world would have lost this connection with the sky - especially sad for the young people in the cities .....

There are now specialist star watching /astrophotography tours to the remote north of Western Australia to take advantage of the dark skies.

I remember as a really young kid, camped out in the country under the stars, so many, so close, and almost being able to reach out and touch them. Of course I knew nothing really of the planets and spotting them then, let alone Dark Emu's. We would take great delight in spotting the "sputniks" whizzing by overhead - what my dad playfully called every satellite no matter the country of origin !




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Old Saturday 13th July 2019, 14:42   #13
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It is sad, Chosun that you can't see the Milky Way. I am really surprised considering how good Australian skies are.

I haven't seen the Milky Way for twenty years from here.
In fact I can hardly see any stars at all.
At 3 a.m. I see the foxes walking down the road brightly lit.
When I was a teenager and near a city centre, I could always count 11 Pleiads with ease, without optical aid.
I didn't need glasses till about forty years old.

The Aboriginal Australians tested had normal sight of 20/6.7 or 20/10 and a best measured youngster 20/4.7.
In addition, they had their own constellations that non indigenous astronomers could not understand.
It was only when the testers used binoculars that they could make out the native constellations, so good was their faint vision.
I haven't seen a study of actual magnitudes, but I suppose 8th magnitude stars were fairly common for Aboriginal Australians.

There were similar reports from south American indigenous sailors who could see distant objects that European sailors only saw with telescopes.

Unfortunately I never got to see Australian skies.

Saturn, Jupiter and the fainter planets are well south of the equator, so you have the best views high in the sky presently.

Regards,
B.

P.S.
My first published letter to a national newpaper was an explanation of the visibility of Sputnik to all the non believers, who said it was impossible to see it.
It really shook the Americans.

Last edited by Binastro : Saturday 13th July 2019 at 14:44.
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Old Sunday 14th July 2019, 11:53   #14
Chosun Juan
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It is sad, Chosun that you can't see the Milky Way. I am really surprised considering how good Australian skies are.

I haven't seen the Milky Way for twenty years from here.
In fact I can hardly see any stars at all.
At 3 a.m. I see the foxes walking down the road brightly lit.
When I was a teenager and near a city centre, I could always count 11 Pleiads with ease, without optical aid.
I didn't need glasses till about forty years old.

The Aboriginal Australians tested had normal sight of 20/6.7 or 20/10 and a best measured youngster 20/4.7.
In addition, they had their own constellations that non indigenous astronomers could not understand.
It was only when the testers used binoculars that they could make out the native constellations, so good was their faint vision.
I haven't seen a study of actual magnitudes, but I suppose 8th magnitude stars were fairly common for Aboriginal Australians.

There were similar reports from south American indigenous sailors who could see distant objects that European sailors only saw with telescopes.

Unfortunately I never got to see Australian skies.

Saturn, Jupiter and the fainter planets are well south of the equator, so you have the best views high in the sky presently.

Regards,
B.

P.S.
My first published letter to a national newpaper was an explanation of the visibility of Sputnik to all the non believers, who said it was impossible to see it.
It really shook the Americans.
Bin, yes I'm afraid the light pollution glow from Sydney stretches all the way from the coast to the mountains (some ~60km .... something like the situation with Los Angeles) - there must be millions of lights on of a nighttime casting an all pervasive glow.

Even out in the country now, the number of huge 24/7 mines light up the sky like it is daytime - the invasive glow stretching far and wide. Looking toward one even from many 10's of 10's of km away seriously degrades the seeing. You have to go to really remote spots.

That's remarkable about Aboriginal eyesight - I obviously didn't inherit my four eyes from that part of the family !

Here is a brief article about the 'Astro-tourism' in Western Australia, though any remote and dark parts should suit equally well. I particularly liked the meteor shower events as a kid when camping out in the country - one every few seconds was quite exciting !
https://mobile.abc.net.au/news/2019-...64?pfmredir=sm

I just came across this while reading something else too https://www.canberratimes.com.au/sto...X16TiF6_ontVk4
and that triggered a memory of a TV doco snippet I saw recently (can't remember the reference) of an outback elder telling of a story of a star on fire that fell from the sky - this was in relation to one of the huge craters formed 100's of thousands of years ago - Wolfe Creek Crater ??

You might like further reading starting here ......
http://www.aboriginalastronomy.com.a...opics/craters/




Chosun

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Old Sunday 14th July 2019, 14:40   #15
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Thank you Chosun.
I will read the links.

As to millions? of stars visible in the outback.

The number of stars to magnitude 6.5 is about 8,700.
However, in a really dark site magnitude 7.5 gives about 26,500.
With only half the full sky visible in any one place, and accounting for atmospheric extinction near the horizon, I would say that 10,000 stars may be visible in the outback to good young eyes.

But Aboriginal Australians might see 20,000 stars when young.
I would think that the strong sunshine might degrade their vision as they age.
In the present they suffer from severe eye defects brought about by an introduced lifestyle, in fact worse than the general population. This is sad.

Indeed photographs can show a million stars, but they show stars much fainter than we can see with our eyes.

Here I am lucky to see 10 stars.
I still haven't see Saturn this year.

Regards,
B.

P.S.
Prof. Hugh Taylor Melbourne University.

'The vision of the Aboriginal people, the fineness of their vision, is better than has been reported anywhere else in the world'.

Prof. Taylor's studies have shown that some Aboriginal people in the NT, WA and SA had 6/1.4 vision. (20/4.7)

6/2 and 6/3 was common. (20/6.7 and 20/10).

They do particularly well with two eyes. It seems their brain/eye system has developed special ways using two eyes.
Their monocular vision is also acute.

Last edited by Binastro : Sunday 14th July 2019 at 15:36.
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Old Sunday 14th July 2019, 16:56   #16
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In fact, seeing the ring gap only means that one is seeing a double or triple planet.
With early telescopes Saturn was seen as a triple planet, and that is what we see with say 20x binoculars.
We only assume that we see the rings when we don't actually see them.
Yes, I notice how my knowledge that I'm supposed to see rings influences what I "see", or think I should. If I didn't know that already, I wouldn't guess it, I'd only say that Saturn was wider in that direction. With a bit more magnification (~20x?) I think Galileo described the appearance as if Saturn had "ears".
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