# Questions tagged [observational-astronomy]

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

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### How could I see Andromeda as large as in this picture?

In this question an image is shown (repeated below) which gives an idea of the "true" angular extent of the Andromeda galaxy in our sky. When I see Andromeda it is usually a bit of a smudge ...
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### Is the scaling in this composite photo reasonably correct?

I came across this image which purports to show what the size of the Andromeda galaxy would be in the night sky if we could see its dim stars with the naked eye. Is this image reasonably correct with ...
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### How are plage regions related to the density of medium and velocity FeII ions?

During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
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### Calculate how many days left for synodic period from particular planet

One of the many tools used in Astronomy are the formulas used to determine Orbital Motion. There are two basic forms of orbits: Sidereal Period Synodic Period For Jupiter: \mathrm{\frac{1}{P} = \...
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### How to fit LOSVD of a galaxy with gauss hermite parametrization

I have recovered the following LOSVD from an elliptical galaxy, that I now want to fit a gauss-hermite-parametrization to and derive the kinematical parameters rotational velocity, velocity dispersion ...
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### Two objects that looked like stars? [duplicate]

My husband and I were on the back porch looking at the stars, and two caught my eye when I noticed they were moving away from us in a zigzag pattern we watched until we couldn’t see them anymore. The ...
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### History, significance and "drama" (if any) of T-Tauri stars, especially the early bits?

In this answer to Can I write a systematic review as an undergraduate and get it published in a journal? in Academia SE I recounted my memory of an experience from circa 1980: I had an initially ...
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### What else can we learn from a Foucault pendulum? Have they ever been used to determine anything more than that the Earth rotates on its axis?

Background Each semester we have to make up projects for each course. This semester I took Cosmology and Astrophysics and we covered a vast amount of topics, from luminosity of stars to Einstein's ...
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### What is being said here about the strange precession of DI Herculis?

The binary star system DI Herculis was brought to the astronomy community by Edward Guinan because it has an observed precession which is far lower than the one predicted by General Relativity. In ...
1 vote
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### What is the current understanding of the results of the merger associated with GW190425? Black hole? Neutron star? Something else?

In an exhibit on gravitational waves I saw a display of events. Each event was in a box, two circles at the top represent the orbiting objects before merger, a single circle below them represent the &...
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### Were there any gravitational wave coincidences between KAGRA and VIRGO and/or LIGO?

KAGRA the Kamioka Gravitational Wave Detector and formerly the Large Scale Cryogenic Gravitational Wave Telescope (LCGT) ...became operational on 25 February 2020, when it began data collection. It ...
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### Pulling spectral data from Hubble Telescope automatically

Libraries currently I am using: Astropy, Numpy, Matplotlib I am looking to create a python script that pulls spectral data (wavelength vs flux chart) from the Hubble Telescope, specifically for Be ...
1 vote
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### Why hasn't the EHT taken an image of Sgr A*?

The Event Horizon Telescope or EHT took an image or the black hole at the center of M87 in 2019, and in 2021 it measured the polarization of the light from M87*. Right after the first image of M87* ...
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### When measuring the spectrum of an object at the zenith, is it better to orient the spectroscopic slit N-S of E-W?

If you were to measure the spectrum of an object while it's exactly at the zenith, how should you orient the slit of the spectrograph to minimise atmospheric dispersion? Is North-South or East-West ...
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1 vote
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### uvotdetect sometimes doesn't make valid .fits files for DS9 to read (Swift UVOT, Heasoft)

I have downloaded galactic center sky images from the Swift database (https://www.swift.ac.uk/swift_live/index.php#doSimpleSearch.php?catname=swiftmastr&searchpos=galactic+center&searchrad=10&...
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### Azimuth and Altitude angle between two points in the sky

I want to know how to correctly calculate altitude and azimuth difference, separately, between two points in the sky. The same way will be with icrs coordinates. For the altitude difference, I simply ...
1 vote
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### What settings should I use for my telescope-mounted smartphone to take night sky pictures?

Last night, I managed to take my first successful picture of a nebula--the Orion Nebula (see picture below). I'm incredibly ecstatic, as before I had been limited to taking images of the moon. I used ...
1 vote
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### What do the letters WHL and LS stand for in the description and name of Earendel star, and other distant objects?

Earendel star's official name includes the abbreviations WHL and LS, as do some other very far-off objects.... What do they stand for?
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### Using optical fibers in astronomy

Why are optical fibers important in astronomy? I have read on the internet that they find applications in many fields including astronomy and this intrigued me and I would like to know what they are ...
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### How is CASA different from SAO DS9?

I was told that CASA is used extensively in Radio Astronomy. However, softwares like SAO DS9 and also python (Astropy) are also used for radio astronomy data analysis. So, what makes CASA different as ...
327 views

### How to choose eyepieces and other accessories for a Celestron 70mm f/5.7 portable refractor?

I have a Celestron Specialty Series Travel Scope 70mm refractor which came with 10mm (40x) and 20mm (20x) eyepieces. Specifications: Focal ratio: f/5.71 Optical Design: Refractor Aperture (mm): 70 mm ...
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### Why does Hubble's F850LP filter have a different shape than all the others shown in Dr. Becky's video "ALL THE DETAILS on Earendel..."?

It will take some time to read through @Pela's excellent answer to Is there a better explanation of this picture showing the very distant star "Earendel"? and to slowly ease myself into it I'...
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### How far away from us was Earendel star when it emitted the light that is just now reaching us?

From what I've read, the look back time is about 12.9 billion light years, and the current distance to the Earendel star is approximately 28 billion light years... How close to us was it when it ...
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### What are the main ways that pulsar "glitches" are noticed and documented? Do they have to be caught in the act of glitching to be catalogued?

This answer to Is there any well-populated list or database of pulsar "glitches"? mentions two large databases; (Jodrell Bank and ATNF's pulsar catalog) but neither question nor answer ...
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### Is the flux density independent of source-observer distance?

A particular observatory is providing the flux density of an astronomical source and only from this information, is it implicated that this particular parameter is unaffected by the distance between ...
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### Does the Cosmic microwave background (CMB) have an amplitude? Does it vary, like the 'temperature' (wavel./freq.) and the polarization?

Somehow, I have never read about this or thought about, until now... Does the number of photons from the CMB hitting us from all directions vary at all?
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### Compute Distance Between Stars

If I have the following information about star A and Star B, how can I compute the distance between A and B? Distance from Sol for Star A Right Ascension/Declination of Star A Parallax/Absolute ...
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### How exactly does SPHEREx implement 96 spectral bands with a linear variable filter across its focal plane?

JPL's mission page for SPHEREx says: The mission will create a map of the entire sky in 96 different color bands, far exceeding the color resolution of previous all-sky maps. Wikipedia's SPHEREx ...
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1 vote
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### How to convert between surface density in JY/beam*KM/S / arcsec2 to mass surface density in Solar masses / pc2

I am interested in studying the gas kinematics of atomic hydrogen (21cm line) for a galaxy and have output I'd like to convert after assuming a model for my data using BBarolo. ...
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### Metric to estimate measuring accuracy

I need help/suggestions on which metric/approach to use. I am trying to estimate pointing precision by measuring the offset of the experimentally measured values from the real, theoretical values, ...
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### Are chirped gravitational wave events generally first identified by searching through libraries of chirps?

Comments below What does "GPU-accelerated butterfly matched filtering over dense bank of time-symmetric chirp-like templates" mean? (GW170817) suggest that for this technique a library of ...
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### For what aspects of cosmology research can a software engineer contribute?

I'm a software engineer and I would love to learn more about cosmology by participating in this field. I'd like to change my career path closer to it and further from web programming. But I don't know ...
3k views

### How can I measure the angle between two stars?

This is a backyard astronomy question. My middle-school-aged son and I would like to measure the apparent angle between two easily-visible stars more precisely than measuring with our outstretched ...
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### What kind of perspective projection is shown in this image?

I’m trying to develop software that overlays sky coordinates over 2d images of the sky taken by an iphone. I’ve done the sky coordinates part, but I’m trying to figure out what kind of perspective ...
1 vote
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### How to convert spectra to log-wavelength and interpolate them into linear spacing in log-wavelength

I want to write a function that cross correlates a spectrum with a quasar template I’d like to ask you how can I convert my flux density vs wavelength spectrum to log-wavelength. It’s not clear to me ...
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### Data of Coronal Holes

I'm working on the Evolution of coronal holes for which I need data of Coronal Holes, I have searched on internet and also done literature survey but didn't find out any open-source catalogue where I ...
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### Is one transit enough to be confident that we detected an exoplanet

Everything is pretty much in the title. I was thinking about the transit method and was wondering if the signature of a transit on the light curve of a star is distinctive enough to only need one ...
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1 vote
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### What would be the highest possible naked-eye apparent magnitude?

What would be the highest possible magnitude $m$ of some star that could be viewed with a naked-eye? I am acquainted with this question, but mine is about the ideal conditions. In order to achieve ...
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### S/N binning of 2D spectral galactic data

I have the 2D spectrum of the ellipical galaxy NGC 4697 taken by a long slit spectrograph. The x-direction (horizontal) corresponds to wavelength and the y-direction (vertical) corresponds to distance ...
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### How is observable matter distributed in the universe?

The observable matter in the universe is distributed and arranged into various structures, including black holes, stars, nebulae, and the much more diffuse regions of the inter-stellar and inter-...
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### Why is it called "The LOFAR 'superterp'"? What is a terp, and what's so super about this one?

Wikipedia's Low-Frequency Array (LOFAR) includes the image below with the caption: The LOFAR core ("superterp") near Exloo, Netherlands. The bridges give an idea of the scale. Question: ...
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### What have I encountered here?

Consider: I tried Google Lens to tell the answer, but it is not giving a true answer. I am using the Android app Stellarium.
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### How did astronomers "measure a large (>40 degrees) misalignment between the black hole spin and the orbital spin" of MAXI J1820+70?

Gizmodo's Funky Black Hole Is Spinning Tilted says: A team of astronomers recently observed an askew black hole just 10,000 light-years from Earth. The black hole’s spin axis is out of alignment with ...
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### Why aren't concentrated solar power plants use for astronomical observations of some type?

Concentrated solar power plants use reflecting surfaces to gather the sun rays for energy production. Currently they sit idle at night and are not used for anything. These have huge collection areas, ...
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### Any package to construct a good segmentation map?

Does anyone know of any package to construct a detailed segmentation map for a given image? So far, I used the SExtractor code. However, I am simulating very faint sources and, sometimes, they are ...
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### Great Attractor's gravity vs Universe Expansion

I would like to know if the trajectory of our galaxy has been calculated because it is usually said that the cosmos is emptying due to the expansion of the universe but at the same time there is a ...
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### How exactly did JWST take a "selfie" of its own primary mirror, and what is the real purpose of this capability?

CNN's Webb telescope's first test images include an unexpected 'selfie' says only: The mirror selfie was captured by a special lens inside NIRCam that can image the primary mirror rather than what ...
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### What exactly did ALMA observe at 20 AU from the "Mega Comet Arriving From the Oort Cloud" that will pass in 2031?

Gizmodo's Mega Comet Arriving From the Oort Cloud Is 85 Miles Wide says: For the new study, Lellouch and his colleagues used the Atacama Large Millimeter Array (ALMA) in Chile to refine the comet’s ...
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