# Tag Info

104

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 amount (it should be 2*23 degrees) over a 6 month time span. Your assumption: If axis it pointed at Polaris at (1), then it should be pointed at a different star ...

57

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 fairly conclusive. You were seeing Ganymede and a Europa/Io combination.

43

This has been done before, so I don't have to go through all the heavy calculations using Rayleigh criterion accounting for atmospheric diffraction and visible light wavelength. Ralf Vandebergh, a Dutch astronomer, professional photographer and veteran satellite spotter has been busy trying to do exactly this since the 2007 and has indeed succeeded on ...

39

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 point in pushing the magnification above 2x the diameter of the instrument, measured in mm. 3 inch, that's 75mm, that's 150x max. Beyond that limit, even under ...

38

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 from Wikipedia: The rise is fast on an astronomical scale – several orders of magnitude over a period of roughly ten days – but very slow on a human scale. An ...

37

(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 is to use the manual mode of your phone's camera and set the ISO down to minimum (100) and the shutter speed down to something like 1/60s. Take a few shots, ...

35

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, maybe they were cut-off by the field-of-view, or possibly as a commenter pointed out, they might be behind the planet. You can test that notion actually, as ...

28

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. It is a pair of stars with similar size and visual magnitude, of about 3.6. Their orbital period is about 169 years, but the orbit is eccentric, e = 0.88. They ...

25

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 setting sun. In the winter in the north, the sun would set in the southwest. And regarding your comment about the text describing the event as "around ...

24

Ralf Vandebergh is one of the best amateur astronomy photographers out there who does spacecraft photography. He is using a 10" (25.4cm) Newtonian telescope, as far as I know, so this is pretty much an off the shelf telescope. He supposedly has imaged spacewalkers on previous ISS and STS missions. Though they are only a few pixels in size, and you cannot ...

24

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 parts: Betelgeuse will explode as a type II supernova, the typical brightness of which is around $M \sim -17$. With a distance of $d\simeq200\,\mathrm{pc}$, its ...

23

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. Therefore I've put this together a little hastily. It's late here and I'll come back in the morning to address any questions or requests for clarification, and ...

22

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 Donald Bruns measured deflections of 2.8 arcseconds of multiple stars. Nasa published a "How To" page for anyone wanting to test GR themselves.

21

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=jupiter+moon+configuration+march+25th+2016+9pm+US+central+time) to try and determine which moons you were looking at, and the answer was quite interesting. ...

20

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 expect. Planetary observation is a learned skill; planetary detail is usually very low contrast. Mars is a small target and you have to use lots of magnification,...

19

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 see how their positions have changed over 2000 years. It's not a lot. The first thing that the Babylonian astronomer might notice is that there is a pole star, ...

18

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 and a tripod would probably be helpful in decreasing shake. I suppose it would affect mobility a little but that's a tradeoff.

18

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 combine. With the right atmospheric conditions they can be very impressive experiences. See for instance this somewhat cross-shaped halo at sunset. Two of the most ...

17

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 and technology involved are far beyond just pointing a toy laser at the Moon. Project APOLLO (Apache Point Observatory Lunar Laser-ranging Operation) is ...

17

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 and on the 29th it sets at about nearly 3am. If the moon is up that will significantly affect the background sky brightness. But when the moon is down, ...

16

A lot of satellites are visible under the right conditions. Usually up to 2 hours after sunset and 2 hours before sunrise. This allows the sun to strike the satellite when you are on the dark side. Depending on the orbit, it will take between 1 and 5 minutes to traverse most of the sky. Usually, they will enter the shadow and you lose sight of them.

16

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 left of it is Mirach (β Andromedae). Given a reasonably dark sky and averted vision, it is possible to see the core of M31 with the naked eye. Since M31 is ...

16

α Centauri (14h 40m, –60° 50′) The most obvious visual multiple system, where orbital changes can be observed is Alpha Cen A+B, (together with Proxima Centauri). The A/B system has an orbital period of 80 years, but because it is so close (1.34 parsec), the semi-major axis is a whopping 17.5 arcsecond. The two stars are currently separated by 5 arcseconds on ...

15

Any telescope can be made to give you the information that you are looking for. The first thing that you will need to know is the location of the ecliptic which varies throughout the year. Or are you looking to find in relation to the the celestial equator? https://en.wikipedia.org/wiki/Celestial_equator Either way, you would start of the same by find ...

15

In your friends picture are more artifacts than the one you showed in the 2nd picture a little bigger. I marked more of them in the picture below (click to enlarge). They are all in a perfect line to the bright light. So these artifacts are caused by the bright light and the lens of the camera. A lens is not flat it's, well lenticular (it's where the name ...

14

Globular clusters occupy an interesting place in the spectrum of composite stellar systems. As you point out, they are highly concentrated populations of stars, and seem to lack any dark matter component, unlike more massive dwarf galaxies. Binary interactions become very important in simulating globular clusters, and interestingly enough (maybe ...

14

The term "color" is a label that humans have assigned to denote the ratio between the intensity at various wavelengths in the three different wavelength bands, or regions, that the human eye is able to perceive. These bands are centered roughly at 430, 545, and 570 nm, but are quite broad and even overlap: Human cone response, normalized to the same height. ...

14

It's probably the planet Venus. You can use an online planetarium (or one of the many mobile apps) to identify objects. This link shows the sky this morning at 6:45am at your location:

14

An analemma shows the position of the Sun in the sky from a fixed location on Earth at the same mean solar time. It gets its north-south shape because of the tilt of Earth's axis makes the declination of the sun change across the year, and the sideways shape due to the orbit nonuniformity. The star analemma would get a point at the same time every sidereal ...

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