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Can we distinguish stars and planets based on twinkling?

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#1 VikrantNarang

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Posted 15 June 2021 - 01:14 AM

Dear Fellow Astronomers,

 

Can we use the phenomenon of twinkling to distinguish planets from stars?

 

To Starry Skies!

 

 


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#2 Dave Mitsky

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Posted 15 June 2021 - 01:30 AM

In general, yes, but I have seen planets twinkle when they were very close to the horizon and the seeing was very bad.

You might see planets twinkling if you spot them low in the sky. That’s because, in the direction of any horizon, you’re looking through more atmosphere than when you look overhead.

https://earthsky.org...le-as-stars-do/
 


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#3 jimr2

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Posted 15 June 2021 - 01:36 AM

Correct, I've seen Venus twinkling several times over the years, for example.



#4 Astrojensen

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Posted 15 June 2021 - 01:44 AM

Just learn the constellations and how the planets look to the naked eye.  

 

 

Clear skies!

Thomas, Denmark


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#5 Tim2233

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Posted 15 June 2021 - 04:17 AM

Completely new to all this - I tried to view what I’m confident was Mars the other night and it was right near the horizon and looked exactly like a star. Is it true that the higher in the sky a planet is, the clearer the view of it is?
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#6 chrysalis

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Posted 15 June 2021 - 04:20 AM

Completely new to all this - I tried to view what I’m confident was Mars the other night and it was right near the horizon and looked exactly like a star. Is it true that the higher in the sky a planet is, the clearer the view of it is?

Typically, yes, for the same reason Dave pointed out - less atmosphere being looked through. But other factors come into play as well.


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#7 Dynan

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Posted 15 June 2021 - 05:22 AM

All depends on the seeing. One night I saw the Moon twinkle. lol.gif


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#8 Ulmer Spatz

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Posted 15 June 2021 - 06:56 AM

Completely new to all this - I tried to view what I’m confident was Mars the other night and it was right near the horizon and looked exactly like a star. Is it true that the higher in the sky a planet is, the clearer the view of it is?

Also keep in mind that the apparent size of Mars changes as the distance between Mars and Earth changes. Mars in mid-October 2020 appeared as a disc 22 angular seconds (22") in diameter. Right now, Mars' disc is only 4" across. At low magnification, casual focusing and only a brief look, Mars could easily look like a star.  


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#9 Tim2233

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Posted 15 June 2021 - 07:11 AM

Also keep in mind that the apparent size of Mars changes as the distance between Mars and Earth changes. Mars in mid-October 2020 appeared as a disc 22 angular seconds (22") in diameter. Right now, Mars' disc is only 4" across. At low magnification, casual focusing and only a brief look, Mars could easily look like a star.


That’s really interesting! Thanks for sharing!! 👌🏼

#10 Ulmer Spatz

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Posted 15 June 2021 - 07:31 AM

I found my little computer sketch. It shows how Mars looked in my 3" reflector at 50x magnification in October 2020. Now imagine that little orange disc five times smaller!

 

 

 

mars and star resized bitmap.jpg

 

  


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#11 Dave Mitsky

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Posted 15 June 2021 - 11:39 AM

There's a graphic illustration of the change in the apparent size of Mars over a year's time posted at https://specials-ima...0.jpg?fit=scale



#12 Dave Mitsky

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Posted 15 June 2021 - 11:51 AM

Sky & Telescope's Mars Profiler interactive tool can be accessed at https://skyandtelesc...ide-is-visible/



#13 sevenofnine

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Posted 15 June 2021 - 01:33 PM

Sometimes stars don't twinkle either. There are moments when they "burn" like planets. Hopefully, you have your scope set up because you're in for a treat. On rare occasions I've been viewing planets when this happens. The atmospheric turbulence is dead calm and the views are extraordinary! I hope this happens for you sometime...it's amazing!! bugeyes.gif


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#14 Echolight

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Posted 15 June 2021 - 03:37 PM

I just look for the big bright white one following the smaller yellow one.



#15 EricSi

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Posted 15 June 2021 - 08:13 PM

As noted above, it is usually but not always the case that twinkling distinguishes planets from stars when viewed with the naked eye.

 

However, with my 10" or 14" telescope brighter stars often do not appear to twinkle.

 

And telling the difference between Neptune and a star is actually not easy, since its tiny 2" to 3" disk is not much bigger than the size that stars appear thanks to the blurring effects of the atmosphere. Uranus is much easier.



#16 Voyager 3

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Posted 16 June 2021 - 02:25 AM

Just learn the constellations and how the planets look to the naked eye.  

 

 

Clear skies!

Thomas, Denmark

A very good method . waytogo.gif

And when you find a "intruder" while comparing the stars of the ecliptic constellations , you can identify it as a planet . 



#17 Deep13

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Posted 23 June 2021 - 05:53 PM

I guess so, but I just keep track of where the planets will be and then look in that direction. There are only five naked eye planets (not including the one you're standing on). For Uranus and Neptune, you'll need a telescope anyway, so checking for twinkling won't help).



#18 ShaulaB

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Posted 23 June 2021 - 06:23 PM

+1 for learning constellations where you live. The ancient Greeks called them "planets" being a word for "wanderers." The stars stay put (over the course of human lifetimes), while planets will move through the Zodiac constellations. The further out a planet is from the Sun, the slower it will wander.

It takes time to learn all this stuff. Relax and enjoy the ride 😊.
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#19 Dave Mitsky

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Posted 23 June 2021 - 07:01 PM

I guess so, but I just keep track of where the planets will be and then look in that direction. There are only five naked eye planets (not including the one you're standing on). For Uranus and Neptune, you'll need a telescope anyway, so checking for twinkling won't help).

Uranus can be seen without optical aid around opposition from a dark site.


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#20 Deep13

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Posted 23 June 2021 - 08:27 PM

Uranus can be seen without optical aid around opposition from a dark site.

Sure, but it's pretty dim. One isn't going to just look up and say "hey, there it is."



#21 Tony Flanders

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Posted 24 June 2021 - 06:00 AM

Sure, but (Uranus is) pretty dim. One isn't going to just look up and say "hey, there it is."

Quite so. Venus and Jupiter are unmistakable because they're much brighter than any star except the Sun. It's occasionally possibly to mistake Jupiter at its dimmest with Sirius, but the difference is quite obvious if you can see them both at the same time.

 

Saturn and Mars are the planets that are easily confused with stars if you're not familiar with the constellations, but even Mars at its faintest is always among the dozen or two brightest points of light visible at any time. So it doesn't take much persistence to notice it every time you look, and eventually realize that it's moving.

 

Mercury is a slippery little devil, always very bright but usually only visible in the brightest part of a bright twilight sky.

 

It's worth nothing that none of the ancient astronomers ever noticed Uranus, despite the fact that they cataloged hundreds of fainter stars. Stars of that magnitude tend to flicker in and out with averted vision anyway, so it would take a super-human memory to notice that one of them is out of place.


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#22 rhetfield

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Posted 24 June 2021 - 03:44 PM

Mercury is a slippery little devil

Especially for those of us with lots of trees and buildings blocking the horizon - I still have not had the opportunity to put a scope on it.


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#23 f74265a

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Posted 24 June 2021 - 04:19 PM

No. Twinkling is caused by instability in the earth’s atmosphere and changing from moment to moment how the light source is refracted. For someone who does not know the constellations, they could not distinguish a brighter star from Mars or Saturn when far from earth. All will twinkle at times.

#24 Dave Mitsky

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Posted 25 June 2021 - 09:57 PM

Sure, but it's pretty dim. One isn't going to just look up and say "hey, there it is."

Be that as it may, it is not correct to say that there are, excluding the Earth, only five naked-eye planets.

 

The same can be said about Mercury, by the way.


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#25 Dave Mitsky

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Posted 25 June 2021 - 09:58 PM

Mercury is a slippery little devil, always very bright but usually only visible in the brightest part of a bright twilight sky.

Mercury can be quite bright at times but it can also be rather dim.

https://theskylive.c...ight-is-mercury (graph)




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