Questions involving basic astronomical concepts or information.

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Equation of the Center constant factor

This questions concerns the longitudinal aspect of the Equation of Time, also called the Equation of the Center. In some sources the equation looks like the following: $\nu - M = 2\varepsilon \sin M$ ...
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13 views

Where can I find the DR12 SDSS dataset in their website

I have to cross-match the SDSS DR12 dataset with that of GALEX but apparently I cannot find the fits document which has the same field as that in GALEX. I have explored the website but I couldn't find ...
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2answers
94 views

What is the effect of the axial precession on the orientation of the planet's orbits?

I am working on an online application to visualize the positions of the planets and to calculate their ephemerides (you find it here, but it is not complete yet). I do not have much knowledge in ...
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2answers
130 views

Calculate time when star is above altitude 30°

To find the best observation time for an object, I'd like to calculate the time when it is 30° or more above the horizon. Local Sideral Time would be sufficient. To include that in my program, I need ...
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1answer
35 views

Books describing first-hand experience of astrophysicists finding planets without skipping actual maths

Are there good references of astronomical texts where we get a first-hand experience of astronomers uncovering astronomical gems using maths alone and not using observation. Observation may have been ...
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1answer
49 views

K-Pg asteroid impact

Is it possible to determine what daytime the Chicxulub impactor striked the Earth 66 mya? Was it day or night, what was the current phase of the Moon etc.? Can sediments, rhytmites or something else ...
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7 views

IDL (particularly GBTIDL) velocity axis explanation?

I have been working with GBTIDL (the Green Bank Telescope version of IDL I suppose) to look at some spectra, and in addition to having the x-axis be frequency or wavelength, you can also have it in ...
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2answers
109 views

Why do we use FITS format for scientific images especially in astronomy? How is it different from formats such as JPEG, PNG etc?

I am new to astronomy and I found that the telescopic dataset can be stored in the FITS format instead of JPEG. Why do we have a special image format just for scientific images?
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52 views

Calculating azimuth from equatorial coordinates

I try to get the azimuth of an object from its equatorial coordinates using this formula: $a = \arctan2(\sin(θ - α), \sin φ * \cos(θ - α) - \cos φ * \tan δ)$ Where φ = geographic latitude of the ...
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39 views

Converting ecliptical to equatorial coordinates

When looking for a formula to convert polar ecliptic geocentric coordinates of an object to equatorial coordinates I find various sources that give these formulae (like Wikipedia): Declination $δ = \...
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1answer
952 views

Are there more stars than all the words ever spoken by humans?

A while ago I saw Neil deGrasse Tyson comparing the number of stars in the universe with the number of words spoken by all of humankind, ever since. I realize both of these numbers are not strictly ...
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51 views

View HD images of space in linux [SOLVED] [closed]

I dont know if this is the correct place to ask this. (I apologize if it isnt) I like browsing through large HD images of space(a weird eccentricity I have), but I always have to go to NASA's image ...
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38 views

What is meant by ionization states?

I am going through the theory of saha equation but I am not able to understand the concept of ionisation state? What are ionization states actually?
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1answer
73 views

Does weight influence Earth's spin? [closed]

If put enough weight on a particular point on Earth's surface disturbing the balance between hemispheres, is it possible that the Earth's spin could change like an unbalanced spinning top?
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2answers
2k views

What would the night sky look like if the Milky Way were the only galaxy in the universe?

I'm curious to know what the sky would look like without any other galaxies out there. How much do other galaxies factor into the stars we see? Does the Milky Way account for most of them? Would the ...
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1answer
83 views

Cosmological redshift and comparing past galaxy sizes

If you were to divide the present-day universe into cubes with sides 10 million light-years long, each cube would contain, on average, about one galaxy similar in size to the Milky Way. Now suppose ...
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1answer
130 views

What is the shape of the Sun's orbit around the Earth taking into account elliptical orbits?

Consider the non-inertial frame that is at rest with respect to the Earth's revolution around the Sun. (Ignore the Earth's rotation around its own axis.) My question is, what is the shape of the Sun'...
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2answers
137 views

How can apparent magnitude be negative?

What is the reason for that scale? Is it because otherwise defining an maximum would be too hard(?). Why do objects that are (apparently) brighter get assigned a smaller number (and down to negative)?
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1answer
49 views

Finding Mass of Star with only Luminosity

Estimate the mass of the star given this formula: $L/L_\mathrm{sun} = (M/M_\mathrm{sun})^{3.5} $ Given $L= 2.752\times10^{28}\,\mathrm{W}$, how do I find the Mass of the star? Thanks for any help.
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17 views

What is the boundary of the space or can the space around us has limits? [duplicate]

When i see this vast universe, I usually had a question in my mind that, what is the limit of the space? I know its childish, but I have this curiosity.
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1answer
55 views

Where can I find/visualize planets/stars/moons/etc positions?

What resources are available to find the positions of planets, stars, moons, artifical satellites, asteroids, and other heavenly bodies?
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2answers
70 views

Determining distance from semi-major axis and eccentricity

I am trying to obtain the distance covered by an object in orbit around the earth within a specified amount of time past its perigee passage. The object is in an elliptical orbit with eccentricity 0.2 ...
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1answer
49 views

Why do we need the “mean” in mean free path?

I was introduced to mean free path in my astro physics class, and the professor posts a question for us to ponder: "Why do we need the "mean" in mean free path?" This further makes me to wonder what ...
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1answer
146 views

Power of the James Webb Space Telescope [duplicate]

I have heard that the JWST will be capable of looking at the early stages of the universe. However I have also heard that it won't be capable of detecting the Oort Cloud that supposedly provides ...
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1answer
36 views

Can angular information be known more precisely than the diffraction limit?

The diffraction limit deals with the ability to determine if two things are separate. I am interested in the ability to find the the centroid of a single object. Imagine a star with no near ...
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2answers
67 views

What exactly is 'eastward movement'

I am reading a book on spherical astronomy. Surprisingly, my problem is not with the mathematics. The author mentions several times words like 'eastward movement' and 'westward movement'. For example, ...
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2answers
49 views

Are any other planetary bodies warming up as well in the Solar System?

Do we have a few decades worth of surface temperature data to compare?
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51 views

Planetary reference systems and time

I am researching into how coordinate systems of solar systems objects are created by reading some of the reports written by the Working Group on Cartographic Coordinates and Rotational Elements (e.g. ...
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1answer
112 views

How were the orbits of planets first mapped out?

I'd like to know how the orbits of planets were first 'mapped out' and to understand the maths behind it. e.g. How do we know what position in space a planet will be at certain time so that spacecraft ...
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1answer
56 views

Black holes and time relation

Why Is it said that if someone is being sucked inside a black hole then he/she may see that time is running slowly?
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15 views

Star Formation in the future [duplicate]

From what I understand stars form in dense clouds of hydrogen and helium molecules. Only so much hydrogen and helium were "created" from the Big Bang or rather formed if you may. Is it conceivably ...
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2answers
254 views

How can we be 13.2 billion light years from another galaxy?

How did we get 13.2 billion light years from the faraway galaxies being discovered with Hubble? If we all started near each other at the Big Bang, and we all travelled slower than the speed of light, ...
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1answer
99 views

Calculation of hour angle

I need to determine Right Ascension and Declination from Azimuth and Altitude, working in C#. The problem is that the formula for calculating hour angle, for some reason, doesn't work. Here's the code:...
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4answers
201 views

Image sets for testing stacking algorithms?

I am looking for sets of astronomical images for testing different kinds of stacking algorithms. The idea is simple: if one has $N$ images of the same object, the signal-to-noise ratio of the ...
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2answers
204 views

How well can we in principle determine $T_{\textrm{eff}}$ of a star?

This is a question about the basics of astronomy, which I have never happened to see a good discussion for. It is about how well would we be able to measure effective temperature of a star, if we had ...
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1answer
56 views

Questions about terminology used for Mars and its moons

I am having difficulty with some terminology: sub-Martian hemisphere of Deimos ... what place on Deimos does it refer to? leading/trailing apex of Phobos ... what place are those? Apex ... in ...
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2answers
129 views

Why you use log to measure metallicity in galaxies?

For example, I saw the next expression for matallicity in a paper: $\log(O/H) + 12$. I understand O/H is the O(Oxygen) to H(Hydrogen) ratio but why is there the number 12? And why the logarithm?
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1answer
67 views

Which force makes planets to continuously revolve around their parent star?

We know that planets revolve around their parent star (or specifically Barycenter), they maintain a specific speed of revolution so that they don't end up smashing into their planet star. Which force ...
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1answer
52 views

Speed of light through the ISM and Wavelength

Articles written about fast radio bursts describe the signal's short-wavelength components arriving before its longer-wavelength components, suggesting energy-dependent time delays in the interstellar ...
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2answers
167 views

Does a week represent something in astronomy? [duplicate]

I know that a day represent the time for the earth to make a full rotation around its own axis and a year is the time for the earth to make a full rotation around the sun. But does a week represent ...
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1answer
97 views

Which is the shape of the sky?

I'm a software developer and I'm developing a planetarium and the first thing that I don't know is: What is the shape of the sky? First, I though that it is a semi-sphere, but searching on Internet I ...
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1answer
55 views

What to do after first year of amateur astronomy? [closed]

I have practiced astronomy as a hobby for a while now. I have an entry-level telescope (6-inch Newtonian). In addition to observing the night sky, I have been studying physics related to optics, ...
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1answer
148 views

Name and language of symbol in astronomy book

I've been working on a programming project involving Peter Duffett-Smith's Practical Astronomy With Your Calculator (3rd Ed.), which has a large number of mathematical/astronomical formulas in it. ...
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2answers
250 views

How to calculate position of an unknown star knowing positions of some other stars from an image?

Suppose I know the coordinates (right ascension and declination) of the stars marked with red. How should I calculate the coordinates of an unknown star, marked with yellow? Searching over the web, I ...
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4answers
1k views

Which is more rare: Lunar eclipse or Solar eclipse?

Which is more rare: Lunar eclipse or Solar eclipse? Please explain why either one is more rare than the other. Thank you in advance for your inputs.
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2answers
611 views

How to plot orbit of binary star and calculate its orbital elements?

I have a set of dates, position angles ($\theta$) and angular separations ($\rho$) for visual binary star. For example: ...
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1answer
81 views

Astronomical databases for machine learning?

I was reading this question about open problems in astronomy. The bounty-receiving answer says that I have just left the field where some colleagues are trying to develop some software to use ...
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2answers
368 views

Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving?

What are some open problems in astronomy that an amateur would have a chance of solving? Suppose the amateur has a PhD in some other field, owns a basic telescope, a set of filters, diffraction ...
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2answers
187 views

Where to obtain Tycho Brahe's data?

I would like to obtain Tycho Brahe's data on Mars. What would be an authoritative source? One source I could find is this page (the data is given as an Excel file) but I have no idea can that be ...
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1answer
121 views

Equations for coordinates of solar system objects

I would like to write a program that visualizes the solar system. To do this, I would need equations for calculating the coordinates of each solar system object at a given time. Where could I obtain ...