Questions tagged [observational-astronomy]

Questions about the techniques and practice of observing the night sky.

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2D Galaxy Spectrum taken by long-slit-spectrograph

I have the 2D data (shape(1125,2058) taken by a long slit spectrograph, which looks as follows: The y-axis corresponds to the distance from the center, where the center is at the most bright green ...
trynerror's user avatar
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Galactic rotation curves data samples: how to get them?

I am aiming to introduce data Science to my High-School students and I thought about giving to them data taken from galactic rotation curves (spiral galaxies at the moment) to stude the flatness of ...
riemannium's user avatar
14 votes
2 answers
3k views

How did asteroid (7482) 1994 PC1 get its "face"? Is it reconstructed from optical or radar imaging, or something else?

(Image sources linked below) NPR's March 10, 2023 Newly found asteroid has a 'very small chance' of hitting Earth, NASA says includes an image of what looks like a computer reconstructed 3D surface of ...
uhoh's user avatar
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What parameters about galaxies can be measured using SAO DS9?

I am trying to determine and plot various parameters for galaxies on SAO DS9. RA & dec, angular size to a fair extent, and contour plotting are a few of the aspects which I could determine using ...
Dhruv Nayak's user avatar
1 vote
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Angular extent of this composite Chandra / JWST image of the Tarantula Nebula?

I thought I’d ask this question here, as I couldn’t readily find the answer looking through online resources. What is the angular extent of the composite Chandra / JWST image of the Tarantula Nebula ...
Bruce Simonson's user avatar
3 votes
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90 views

How will China's Xuntian space telescope use its Terahertz capability? THz Spectroscopy? Imaging? Something else?

An Update on the Chinese Space Station Telescope Project Hu Zhan, National Astronomical Observatories, CAS, KIAA, Peking University, On behalf of the CSST Team, ISSI-BJ Workshop: Weak gravitational ...
uhoh's user avatar
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Did this satellite streak past the Hubble Space Telescope so close that it was out of focus? If so, how close was it?

The new Nature Astronomy paper The impact of satellite trails on Hubble Space Telescope observations (Kruk et al. 2023) describes an AI-based object classification method used to find satellite trails ...
uhoh's user avatar
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Effective gain when stacking N frame images

I am trying to understand how to derive the effective gain in [electrons / ADU] when stacking N frame images in different (summed, averaged, or medianed) ways. I found the effective gains for the ...
cosmozaka46's user avatar
4 votes
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78 views

What was the formation of three blinking dots, looking back using Stellarium [closed]

On February 28, 2023, we were watching the stars around 19:45 from the ground in central Netherlands when we saw three bright blinking dots moving along the sky. The dots were arranged in a triangular ...
Ivana's user avatar
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Small bright constellation on the photo

I did a photo of the night sky and wanted to find a constellation on it. I've suggestion that it is Delphinus constellation. Could you please help me figure it out. Also, I'm curios about good way to ...
pacman's user avatar
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Right ascension of a star and local sidereal time

If I'd like to watch star like Betelgeuse that has coordinates - right ascension 05h 55m 10.30536s and declination +07° 24′ 25.4304″. If my local sidereal time is 05h 55m 10.30536s does it mean that ...
pacman's user avatar
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1 answer
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Telescopes with equatorial mount and "catching" stars

I have a misunderstanding of principles behind using telescopes with equatorial mount (I don't have it yet, only trying to grasp the idea). For example, I would like to watch Betelgeuse in the ...
pacman's user avatar
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3 votes
1 answer
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How to obtain luminosity distance from a light curve

I have some light curve data of a SN Ia from which I want to find the luminosity distance $D_L$. How can I do it mathematically? I'll then try to implement the answer using Python.
Abdullah's user avatar
1 vote
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To set up parameters for the sherpa tool

How to set the parameters - photon index and metal abundance in the CIAO Sherpa tool for an x-ray source? I am trying to analyze a bright x-ray source using the data extracted from the Chandra archive....
Bivu Wagle's user avatar
1 vote
1 answer
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Interpreting the color of galaxies in deep field images

The HST produced some deep field images in mostly visible light, which contain thousands of galaxies that range in color from white to red (e.g. see here). I understand that the interpretation of ...
user1247's user avatar
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12 votes
2 answers
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Why hasn't VLBI been used to try and image giant exoplanets?

A Jupiter-sized object at 10 pc subtends an angle of 0.0001 arcseconds (100 micro-arcsec) at the Earth. The Event Horizon Telescope interferometry network is capable of a (demonstrated) angular ...
ProfRob's user avatar
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Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?

NASA’s James Webb Space Telescope has taken very blurry "photos" of exoplanets around distant stars, such as the exoplanet HIP 65426 b, in different bands of infrared light: My question is, ...
user3163495's user avatar
2 votes
0 answers
59 views

Computing the sky coordinates using astropy

I need your help with an error I have been receiving while trying to obtain the sky coordinates using astropy module in python. The code looks like the following, ...
CTZenScientist's user avatar
2 votes
1 answer
80 views

How to calculate Local Sidereal Time from RA of a star and Longitude of Observer

I have been banging my head against a wall trying to understand these time conversions and the relation between all of these astronomical measurements. This is the question I am currently working on, ...
Chance Law's user avatar
2 votes
1 answer
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What's the formula of SNR (Signal to Noise Ratio) to dipole antenna array (eg, LOFAR) look like?

It was wellknown that the SNR of single dish telescope reads $$s/n=P_s/P_n=\frac{P_s}{T_n}\sqrt\frac{t}{B},$$ where $P_s$ is the collected power, $T_n$ the noise temperature, $t$ the measure time and $...
Hunter's user avatar
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How has the resolution of astronomical spectrographs improved over time?

Is there something like a Moore's law for spectral resolution? Maybe a chart from which one could extrapolate?
2080's user avatar
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3 votes
1 answer
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Stellar classification spectral lines: chemical abundance vs temperature

I'm an amateur who watched the Cosmos episode on Cecilia Payne's contributions to stellar classification, which I liked. I've been going down a rabbit hole on this and and I have a question for ...
Stephen's user avatar
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Why is the angle at which the sun sets the same as your latitude? [closed]

I learned in class that the sun sets at an angle when it is not an equinox. I also learned that the angle at which it sets is a good approximation of your latitude on earth. I am having trouble ...
Susanoo D Ace's user avatar
8 votes
1 answer
876 views

Is Barnard's star an M4 red dwarf or an M0? Why is it called an M4.0V?

I have tried to figure this out, but cannot find an answer anywhere... Are, perhaps, astronomers unsure of its exact spectral class? (I have heard that red dwarfs are usually variable... to an extent....
Kurt Hikes's user avatar
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2 votes
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"First gamma-ray eclipses from ‘spider’ star systems" - but have other types of gamma-ray eclipses been observed?

The January 28, 2023 NASA News item NASA’s Fermi Detects First Gamma-Ray Eclipses From ‘Spider’ Star Systems begins: Scientists have discovered the first gamma-ray eclipses from a special type of ...
uhoh's user avatar
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3 votes
1 answer
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Are these images of the same nebula?

This image from the Spitzer telescope is supposedly of the Orion nebula. But this image from the Chandra telescope also claims to be of the Orion nebula. I have been unable to confirm either of these ...
Deko Revinio's user avatar
1 vote
0 answers
66 views

Which stars are elliptical galaxies constituted by?

I know that elliptical galaxies are old galaxies, with almost no star formation and an old stellar population. This can be seen by their dominantly red spectra in the optical. I am trying to get a ...
trynerror's user avatar
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7 votes
1 answer
311 views

How do amateur astronomers do stellar spectroscopy?

This question consists of 2 parts: How can amateur astronomers measure the spectrum of stars? In addition to diffraction gratings, what equipment do they use (like telescopes, and the focal length ...
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Half Moon illumination evening and morning

With a first quarter Moon I notice that in the evening the Moon is lit from the east and the following morning the opposite limb west is illuminated. I understand that my position has changed by 180 ...
NoelC's user avatar
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1 answer
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How does one actually fold a light curve?

I'm studying the variable stars (periodic variables with brightness changes repeating over time), and to examine the shape of the light curve it is useful to fold the data points at this period and ...
Saturn.'s user avatar
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0 answers
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Formation scenarios for elliptical galaxies?

I am trying to get an overview of the latest research on different formation scenarios for elliptical galaxies and filter out old scenarios in the literature that are today proved to be not sufficient/...
trynerror's user avatar
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0 answers
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What is the galactocentric aberration?

At the Wikipedia about an aberration, there is the phrase: a recommended galactocentric aberration constant of 5.8 µas/yr What is the galactocentric aberration? How is it calculated correctly? An ...
Imyaf's user avatar
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5 votes
2 answers
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What is meant by " elliptical galaxies stabilize due to the chaotic motion of stars"?

I read that elliptical galaxies stabilize due to the chaotic motion of stars. As I understand that means that the stellar motions are more nearly random in direction. So they perform independent ...
trynerror's user avatar
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3 votes
1 answer
271 views

Why does the altitude-azimuth mount have a blind spot near zenith?

I understand the subject mathematically. Azimuth of the celestrial object under track changes a finite 180 degrees instead of a infinitesimal amount as the body passes zenith. This would require ...
Cici Xu's user avatar
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3 votes
1 answer
365 views

Conversion to Jy of Hubble WFC3 units (electrons/s) and of Spitzer IRAC (MJy/sr)

I am trying to figure out how to convert the units of some FITS files to Jy. These files refer to observations in different bands using different instruments. I list them below with my way of ...
lol's user avatar
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2 votes
1 answer
117 views

Could two-way mirrors be used to completely eliminate obstruction for a reflector telescope?

The secondary mirror on a reflecting telescope obstructs some of the light coming in and the spider vanes that hold up the secondary mirror cause diffraction spikes when imaging. Some people prefer ...
chowder's user avatar
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4 votes
1 answer
215 views

What is the probability that a photon that enters the aperture is registered?

If I want to derive the probability that a photon that enters the aperture of a telescope is detected, how do I do that? This should be closely related to the quantum efficiency of a telescope, but ...
JanKanis's user avatar
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3 votes
3 answers
229 views

Viewing black holes?

How could you possibly see a black hole when there are stars etc in front of it and then the matter being drawn into it , all you would view surely would be the objects in front of the black hole ?
Big4's user avatar
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3 votes
1 answer
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How can we make sure that it is physically the same source when we do cross matching?

When we go through multiple astronomy catalogs, we often do Cross-matching. We compare the position parameters $(\alpha, \delta)$ of different sources (galaxies, quasars, etc.) in the equatorial ...
Chang's user avatar
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2 votes
2 answers
233 views

Right ascension and declination visible at that local time and location

If I know the local time of an observer and her/his latitude and longitude, how can I know which stars are visible? I'm developing a planetarium software using the Hipparcos Catalogue. I have also ...
VansFannel's user avatar
19 votes
6 answers
6k views

Could we detect the light of cities at night in other solar systems?

Would it be possible to see electric lights on distant planets using current telescopes?
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-2 votes
3 answers
934 views

Why is Earth 1/3 the age of the universe?

The Earth is 4.6 billion years old The universe is 13.8 billion years old. 3 times the age of the Earth Are there other planets with ages that are close to say 1/4 1/5 etc the age of the universe? Why ...
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6 votes
1 answer
300 views

Can LIGO distinguish rotating and non rotating black hole collisions?

I am assuming two rotating black holes create gravitational waves as they collide.
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6 votes
2 answers
273 views

A what distance could we see the Sun?

How far away can we see the Sun with the naked eye? How far with an amateur telescope? And with the James Webb telescope? In my own calculations the Sun would appear magnitude 6 at 56 ly, magnitude 8 (...
HugoF's user avatar
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2 votes
0 answers
84 views

How to know if the star is on the west or east side calculating hour angle and sideral hour

I have an exercise where I need to calculate the hour angle (H), declination (δ), latitude (φ) and the sideral hour at the moment the star passes through the 18 hour circle. Given are the right ...
MoritzMoreira's user avatar
4 votes
1 answer
278 views

Why is there an extra peak in the Lomb-Scargle periodogram?

I was messing around with some radial velocity data from NASA's Exoplanet Archive and the Lomb-Scargle periodogram for Pegasi 51 yielded two very sharp peaks. One corresponds to about 4.23 days which ...
chuffyduffy's user avatar
2 votes
1 answer
155 views

Can we simply multiply a positive value to each pixel in order to enhance contrast and to discard Time Delay Integration technique?

As shown in the figure below, the Time Delay Integration (TDI, the right side of the figure) is aimed at accumulating multiple exposures of the same (moving) object, effectively increasing the ...
Rocky Tseng's user avatar
7 votes
1 answer
152 views

SKA 101: How will it "perform the most precise tests of Einstein's theories" and Australia & South Africa arrays be "made to work seamlessly together"

The BBC's December 7, 2022 SKA: Construction to begin on world's biggest telescope includes the following: It will perform the most precise tests of Einstein's theories and The first major ...
uhoh's user avatar
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3 votes
0 answers
73 views

Mega Telescope using gravitational lensing and interferometry

I have been thinking about this crazy telescope idea, but I am not smart enough to understand if it's technically possible. I understand from an engineering and practical point of view it's a long way ...
Adrian's user avatar
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4 votes
1 answer
235 views

What is the brightest nameless star?

Bright stars in the night sky traditionally have their own proper names, like "Sirus" or "Canopus". Most stars don't have names, but instead catalogue identifiers, like the Bayer ...
SE - stop firing the good guys's user avatar

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