106 votes
Accepted

If Earth is tilted, why is Polaris always above the same spot?

You are correct that the axis of the Earth's rotation is tilted with respect to the plane of its orbit by 23 degrees. But it is incorrect that the direction that the axis points changes by a large ...
user avatar
  • 7,085
59 votes
Accepted

Did I see another planet?

You don't say what time you were looking. Here is a screenshot from Stellarium at 10pm Wisconsin time on 25th March 2016. Jupiter is in the ESE, but the altitude is a bit lower than 60 degrees. Seems ...
user avatar
  • 116k
42 votes
Accepted

How much magnification is needed to see the planets of solar system?

You're probably asking the wrong question - which I am going to answer anyway, and after that I am going to answer the question you should have asked instead. As a general rule, there isn't much ...
user avatar
39 votes
Accepted

What would happen if someone had a telescope and watched Betelgeuse when it goes supernova?

No, it would not be a problem. Supernovae are not at all like flashbulbs – they brighten over a period of many days and dim again even more slowly. Here are a number of different light curves taken ...
user avatar
  • 7,390
38 votes

Please check my Mars photo

(Much of this echoes what antlersoft says in their answer) For a phone photo through the eyepiece that looks about right to me! The size... the brightness... both are as I expect. What you could try ...
user avatar
  • 1,498
35 votes

Did I see another planet?

That should be Jupiter and his 4 Galilean moons. They are usually very well visible even with very cheap equipment and a nice experience for amateur astronomy. On your picture 2 of them seem missing,...
user avatar
34 votes
Accepted

Why are fewer stars seen next to the horizon?

When you look towards the horizon you are looking through a much greater thickness of air. The air does absorb some light. Dense air near surface absorbs more, and if you look towards the horizon ...
user avatar
  • 88.9k
34 votes
Accepted

How can I measure the angle between two stars?

A tool such as Jacob's staff or a cross-staff can be used. This is essentially two pieces of wood in a cross shape, one of which can slide on the other. By Original: Fantagu Vector: Majo statt Senf - ...
user avatar
  • 88.9k
29 votes

What it the outer part of the sun, that we see with our eyes, called?

I think you're talking about the effect of a "fluffy glowing ball" around the solar disk, shown on the right in this photo: This is called solar aureole, and it's caused by the aerosols in ...
user avatar
  • 606
28 votes

Are there any double stars that I can actually see orbit each other?

𝛾 Vir (12h 42m, –01° 27′) Probably Porrima, $\gamma$ Vir, is the best candidate for most observers in the Northern Hemisphere to see changes in a binary orbit, particularly using a small telescope. ...
user avatar
  • 1,240
25 votes

What would happen if someone had a telescope and watched Betelgeuse when it goes supernova?

If you insist on observing the exploding Betelgeuse at peak brightness, you could potentially damage your eye. The complete answer enters the realm of physiology. Here I'll discuss the astronomical ...
user avatar
  • 32.3k
25 votes

Was this an astronomical phenomenon observed in 1689?

This is a really interesting question! One thing to note is that since it appeared in the northeast at sunset, it is nowhere near the sun - in fact, it is pretty much in the opposite direction as the ...
user avatar
  • 4,259
24 votes

Is it possible to do moon sighting in advance for 5 years with 100% accuracy?

Note: this answer was posted under duress; though I mentioned in a comment under the question that I was composing an answer, several users have decided to close the question out from under me. ...
user avatar
  • 31.6k
23 votes
Accepted

Was the Sun's gravitational lensing observed in other solar eclipses than the one in 1919?

Yes, observations of this kind are within the technical scope of amateur astronomers. Several groups succeeded in replicating the experiment during the 2017 eclipse that crossed the USA. For example ...
user avatar
  • 88.9k
23 votes
Accepted

Can you see something active in the sky apart from satellites? Can there be amateur time-domain astronomy?

If it moves or flashes it isn't astronomy, it is meteorology or technology. There are only a few exceptions to this: Meteors are an atmospheric phenomenon, and a meteor will appear to move rapidly ...
user avatar
  • 88.9k
22 votes

Did I see another planet?

This appears to be Jupiter and two of its four "Galilean" moons, being the four discovered by Galileo with his telescope in 1610. I searched with Wolfram Alpha (http://www.wolframalpha.com/input/?i=...
user avatar
22 votes

What is that donut-shaped object I see in my telescope?

This is because your image is not in focus. So you’re seeing the shadow of the secondary mirror. You should have a knob near the eyepiece, that you can turn to adjust focus. You need to turn it, one ...
user avatar
20 votes
Accepted

How much does the sky change in a few thousand years?

Here's part of the sky in the year 1 It is part of the sky you may know well, Orion and the dogs. I've marked the current positions of Sirius, Procyon and Betelgeuse, with green markers so you can ...
user avatar
  • 88.9k
20 votes

Please check my Mars photo

It's very difficult to get any kind of picture just holding your phone up to the eyepiece, and the picture you posted is overexposed and probably motion-smeared, but other than that it's what you'd ...
user avatar
  • 2,701
20 votes

What is that donut-shaped object I see in my telescope?

This is a heavily de-focused image (possibly taken through cloud looking at the orangeish "glow" to the right). The dark center of the "donut" is the shadow of the secondary mirror ...
user avatar
  • 7,170
19 votes

Why can I see sometimes a horizontal half moon instead of a vertical one?

It occurs because the lit half of the moon points towards the sun, along a great circle in the sky. The half-moon will be 90 degrees away from the sun in the sky. So by (say) 8pm (at equinox for ...
user avatar
  • 88.9k
19 votes

Was lunar libration first observed or first predicted? In either case, who was the responsible party?

The variable speed of the Moon on the celestial sphere has been known since ancient times. The Babylonians made ~7 centuries of daily astronomical observations from around 700 BC. That data was the ...
user avatar
  • 9,407
18 votes
Accepted

How do I prevent or reduce shake when observing with binoculars?

Don't hold the binoculars in your hands. Humans are made of meat. wobbly wobbly meat. There's apparently devices that let you mount binoculars on tripods - (this google search would be a start). Those ...
user avatar
18 votes
Accepted

What's the white glow around this star?

Astrometry.net has identified your star field as being part of the Andromeda constellation. The diffuse object in the centre of your image is the Andromeda Galaxy (Messier 31). The bright star to the ...
user avatar
  • 1,536
18 votes

Was this an astronomical phenomenon observed in 1689?

That is hard tell; from your description it reads like a spectacular halo phenomenon. They are more common when the sun is still up in the sky, but even after sunset many are possible and they can ...
user avatar
  • 11.1k
17 votes
Accepted

Visibility of human activity on the moon

The video is hilariously wrong. However, the principle of laser ranging is more or less right, and it does require the reflectors left behind by the astronauts on the Moon. It's just that the physics ...
user avatar
17 votes
Accepted

How will Starlink affect observational astronomy?

tldr; some modelling has been done with a lot more to do, but generally the impact of these constellations is fairly negative, but potentially manageable. Ok, there's a lot to unpack here. First ...
user avatar
17 votes
Accepted

Stargazing (Tenerife) - different quality today and yesterday

If you want to see the milky way, you really need the moon to have set. The moon sets about 50 minutes later each day, so you will need to go later. On the 28th of July, the moon sets at about 2 am ...
user avatar
  • 88.9k
17 votes
Accepted

Opportunities to see a near earth object via unaided eyes or binoculars?

Your best viewing opportunity will be 99942 Apophis which will pass Earth on April 13, 2029, where it will pass about 19,600 miles from Earth; look out for that. According to Wikipedia: On that date, ...
user avatar

Only top scored, non community-wiki answers of a minimum length are eligible