Skip to main content
107 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 ...
JohnHoltz's user avatar
  • 8,032
60 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 ...
ProfRob's user avatar
  • 153k
50 votes
Accepted

How does the earth cast straight and reversed shadows on the moon?

Aha! I think you'll find that the answer is that those are not photos of Earth's shadow on the Moon at all! Look at the photo of the Earth and the Moon seen from the spacecraft Voyager 1 as it was ...
uhoh's user avatar
  • 30.8k
45 votes

How does the earth cast straight and reversed shadows on the moon?

There is already a good and correct answer from @uhoh, but I thought I’d add another to show off some of my favorite teaching images, and to comment on what we do learn from lunar eclipses. The ...
Eric Jensen's user avatar
  • 4,894
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 ...
Mark Olson's user avatar
  • 7,640
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 ...
Aaron F's user avatar
  • 1,670
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,...
AtmosphericPrisonEscape's 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 ...
James K's user avatar
  • 123k
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 - ...
James K's user avatar
  • 123k
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 ...
Ruslan's user avatar
  • 967
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. ...
amateurAstro's user avatar
  • 1,595
27 votes

Small bright constellation on the photo

The object inside the red circle is indeed The Pleiades. Note that it is not a constellation, it is an open star cluster located in the constellation Taurus. A good way to identify constellations in a ...
Albert's user avatar
  • 2,172
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 ...
pela's user avatar
  • 38.6k
25 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. ...
uhoh's user avatar
  • 30.8k
25 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 ...
James K's user avatar
  • 123k
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 ...
Eric Jensen's user avatar
  • 4,894
24 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 ...
Pierre Paquette's user avatar
24 votes

Recurring flying object near the Big Dipper

An orbiting satellite becomes far more visible when there is a perfectly aligned angle between the sun, your eye, and a reflective surface on the satellite (usually the solar panels). Imagine looking ...
Darth Pseudonym's user avatar
23 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=...
maguirenumber6's user avatar
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 ...
James K's user avatar
  • 123k
23 votes

Do these results mean that I have found this exoplanet?

It could be an exoplanet transit (but that doesn't mean it is). The star in question, TIC92352620, is an F8 main sequence star, which would be much larger than any plausible planet. If a planet ...
ProfRob's user avatar
  • 153k
21 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 ...
astrosnapper's user avatar
  • 8,357
21 votes

What is this celestial phenomenon in the video?

That is a re-entry of an artifical satellite, or rocket body. (As Darth Pseudonym mentions, its actually the upper stage from the Soyuz MS-25 launched two days earlier). It's certainly not a comet. ...
James K's user avatar
  • 123k
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 ...
James K's user avatar
  • 123k
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 ...
antlersoft's user avatar
  • 3,455
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 ...
James K's user avatar
  • 123k
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 ...
PM 2Ring's user avatar
  • 14.9k
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 ...
Mick's user avatar
  • 1,546
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 ...
planetmaker's user avatar
  • 19.9k
18 votes
Accepted

Identify stars in image from James Webb

None of the stars in the image of SMACS 0723 are bright enough to be shown in the picture you've provided of Volans. SMACS 0723's at right ascension 07h 23m 19.5s, declination -73° 27′ 15.6”, and the ...
notovny's user avatar
  • 4,788

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