Post by: Just thinking on 07/07/2021 20:25:11
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Post by: Bored chemist on 07/07/2021 21:14:10
is it light diffraction is it the atmosphere or is it due to the lack of resolution.All three in various proportions.
Post by: Just thinking on 07/07/2021 21:37:18
All three in various proportions.There have been some astronauts that say when they were in space the stars are so much sharper and of course the Hubble telescope can provide very sharp images but still not true to reality. My image is very poor mostly due to bad atmospheric conditions that night. plus I used a Cassegrain telescope better suited to the planets. I can't blame tracking as it was a very fast image.
Post by: evan_au on 08/07/2021 10:42:55
- Thermal currents act like a continually changing distortion which makes the image dance around on the detector, and smears out the image
- Some amateurs take a video of the star/planet, etc, and use software to select the frames that are less distorted, adjust the position to account for the moving focus, and then "stack" the good frames to get quite a good photo.
- Professional telescopes are located on high mountains, to get above most of this atmospheric turbulence.
- Really big telescopes shine a laser into the upper atmosphere, where it's return is distorted just like light from the star. With some fancy maths and a mirror that can be distorted on a millisecond scale to cancel the atmospheric distortion, you can get images that are (in some respects) as good as Hubble.
Diffraction also imposes a fundamental limit to the resolution of a telescope which is related to the diameter of the optics.
- That's why a professional 8 meter telescope has better resolution than your 8 inch telescope.
See: https://en.wikipedia.org/wiki/Adaptive_optics
https://en.wikipedia.org/wiki/Optical_resolution#Lens_resolution
Post by: Just thinking on 08/07/2021 12:24:02
b.PNG (1308.09 kB . 610x879 - viewed 4794 times) a.PNG (779.43 kB . 430x905 - viewed 4869 times)Looking at stars through the atmosphere is like viewing the bottom of a lake through a rippled surface.Hi Evan what you say is so true. I live near Bathurst and find that during spring and autumn seem to be the better times for observing as winter is just too damp and foggy and summer has too much atmospheric disturbance with hot and cold air mixing. good nights or mornings can be few and far between. P.S a couple of my telescopes.
Post by: evan_au on 09/07/2021 09:57:50
Quote from: Just thinking
I live near BathurstIf you live near Bathurst, you may find some local interest in the Space Nuts podcast (if you aren't listening already).
Highly recommended if you have an interest in astronomy, no matter where you are in the universe ..
See: https://spacenutspodcast.com/
Post by: Just thinking on 09/07/2021 13:36:41
If you live near Bathurst, you may find some local interest in the Space Nuts podcastThank you Evan I have not looked at that site but I will thank you for the link.
Post by: Bored chemist on 09/07/2021 14:42:20
P.S a couple of my telescopes.Why two? Is it one for each eye?
Post by: Just thinking on 09/07/2021 16:43:17
Why two? Is it one for each eye?I'm just addicted to optical instrements my wife says how many telescopes do you need I say as many as I can afford. The best binoculars for the night sky are 7x50 and that is definitely for both eyes.
Post by: Bored chemist on 09/07/2021 17:22:55
He thought for a moment and said "N; where ownership of N+1 bikes would lead to divorce".
I keep thinking I should get a telescope but I live in a city; the only thing that light pollution doesn't screw up is the Sun (and maybe the Moon, on some nights).
Post by: Just thinking on 09/07/2021 18:39:04
the only thing that light pollution doesn't screw up is the Sun (and maybe the Moon, on some nights).Unless you have the sickness that I have for telescopes and optics what you say is so true. It is better to see all the wonders that other people have captured in the night sky with their better equipment. I'm a bit of a try hard but there are images that are available that put my attempts to shame. It's all fun and games with a dam price tag.
Post by: hamdani yusuf on 13/07/2021 10:31:08
Post by: Just thinking on 13/07/2021 10:57:20
Have Starlink satellites bothered you yet?Hi, Hamdani thank you for asking I can't say that they have bothered me but about one year ago my wife was outside in the evening and called out to me to come out side and there they were coming from the south heading north I counted 56 of them but apparently, there is 60 in total at least that lot. It was a very dark clear sky and thay had me fixated it took about 5 minutes for them all to pass. That was the first time and the only time I have seen them. I believe there are many more trains of them orbiting now. Have you seen them yet?
Post by: hamdani yusuf on 13/07/2021 22:24:28
Have you seen them yet?I only saw them from Youtube videos.
I only have a small telescope made for kids education. Unfortunately, light as well as air pollution make it hard to see the stars. Even in clearest night, only a few brightest stars and planets are visible to the naked eye.
Post by: Just thinking on 14/07/2021 04:12:06
Unfortunately, light as well as air pollution make it hard to see the stars. Even in clearest night, only a few brightest stars and planets are visible to the naked eye.I see you are in the tropical zone and that is a rather high humid air further to your south would be quite acceptable skies.
Post by: Europa on 21/07/2021 16:45:32
Why do stars look larger than they really are is it light diffraction is it the atmosphere or is it due to the lack of resolution. I have noticed the same effect when I see car headlights in the far distance the headlights appear to be many times larger than they really are. I have viewed a number of double stars and this enlargement is noticeable even with a telescope with an aperture of 8 inches. The gap between the stars can be less in size than the stars themselves. In reality the gap between the double stars would be greater than many hundred or even thousands of times than that of the diameter of the stars. The true size of the stars is never seen even viewed through a telescope with considerable magnification they would really appear as little more than that of a pinhead. Have you noticed this?What are they really?
Post by: Just thinking on 21/07/2021 17:12:59
What are they really?Well, the two stars in the picture are 4.3 light years from earth and both of them are very close to the size of our sun the image is magnified about 1000 times. on a scale, it is like two golf balls with a separation gap of 300 feet between them so the image looks nothing like that. The image is more like two 300 feet in diameter balls with a 300 foot gap.
Post by: Europa on 21/07/2021 19:30:36
Again you know so much about the universe but can not name what is in my pants pocketWhat are they really?Well, the two stars in the picture are 4.3 light years from earth and both of them are very close to the size of our sun the image is magnified about 1000 times. on a scale, it is like two golf balls with a separation gap of 300 feet between them so the image looks nothing like that. The image is more like two 300 feet in diameter balls with a 300 foot gap.
Post by: Bored chemist on 21/07/2021 19:37:51
Again you know so much about the universe but can not name what is in my pants pocketPeople care about the universe.
Post by: evan_au on 21/07/2021 23:42:03
Quote from: Europa
Alpha Centauri and Rigel Kent...What are they really?They are stars - actually part of a triple-star system (the third one is much fainter).
See: https://en.wikipedia.org/wiki/Alpha_Centauri
We know by spectroscopy that they are balls of plasma (great balls of fire!), and we know these collapse under their own gravity to form a sphere (with an equatorial bulge due to rotation).
The picture does not look like a sphere at all. That is because you are looking at it through the dancing atmosphere, and through a telescope with a resolving power far too low to resolve the surface of the star. To see the actual surface, you need to use a technique like interferometry.
There is a video showing atmospheric disturbance in motion here: https://en.wikipedia.org/wiki/Speckle_imaging#Explanation
Post by: Just thinking on 22/07/2021 04:44:10