Questions tagged [observational-astronomy]

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

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2
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1answer
49 views

Is there anything like a timelapse showing the Alpha Centauri stars orbiting around each other?

It is my understanding that the angular separation between Alpha Centauri A & B is more than enough for even amateur telescopes to resolve as 2 separate stars. Going by the plot below, over the ...
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What would a red giant Sun look like from Proxima b?

As of now, Proxima b is the only confirmed planet (or dwarf planet if it didn't clear its orbit - sorry, couldn't resist) around Proxima Centauri, the nearest-known star to the Sun about 4.2 ly away. ...
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How to explain the equation 'Altitude of a star at culmination = co-latitude + declination'?

Altitude of a star at culmination = co-latitude + declination. I understand that the co-latitude is equal to the altitude of the celestial equator (since it is 90 degrees away from the NCP). I also ...
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1answer
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What exactly are “H30α and He30α images”? (ALMA)

I ran across this paper's title η Carinae: high angular resolution continuum, H30α and He30α ALMA images (arXiv) and see that the body of the paper also mentions "H40α, H30α and H29α". What ...
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Is “Zero Shadow Day” necessary to perform Eratosthenes' experiment?

Eratosthenes experiment to find the circumference of the Earth is usually said to be performed on the Zero Shadow Day at Syene. Is it necessary? Can this experiment be performed on any day for two ...
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Deciding optical factors between a refractive and reflective space telescope optics as a function of aperture? (visible light)

Reading Yale News' Lighting a path to Planet Nine: To detect objects that are otherwise undetectable, Rice and Laughlin employ a method called “shifting and stacking.” They “shift” images from a ...
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Are there any ALMA or JCMT detections of extraterrestrial phosphine that have been confirmed by direct sampling?

Please note that I am not a professional astronomer but an interested layman. I've informed myself on the matters below by perusing arXiv--there are likely other publicly-accessible primary sources I ...
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What was the train of lights (30+ in a row) that went south toward north then disappeared tonight in Turnersville Texas? [duplicate]

The lights were bright and looked like stars that moved together in unison in the formation of a Double forward slash Ex: // but nearer together made up of (I’m guessing from what I saw)at least 30+ ...
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3answers
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How can I see a nebula?

I've recently been seeing a bunch of pictures of nebulae and I'm just fascinated by their beauty and complexity. Is there any kind of telescope that would make it possible to view it from here on ...
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1answer
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Photometry extinction correction magnitude

I am learning photometry and I am wondering is the uncorrected extinction instrumental magnitude always less than the corrected extinction instrumental magnitude when applying transformation ...
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How does the Helioseismic and Magnetic Imager (HMI) compute the Magnetic Activity Index (MAI)?

I am looking for a description about how this number called Magnetic Activity Index (MAI) is calculated. All I know is that the processing pipeline of the instrument HMI calculates it. But I would ...
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1answer
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Expanding our observable universe suggestion

Firstly, regarding the observable universe there is a certain radius of a circle, and we cannot see further than that. It is understandable, that due to photons travelling at a certain speed we can ...
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1answer
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How is the height of the Great Red Spot measured?

This answer states that the Great Red Spot is getting taller. This means that we are able the determine the spot's height. How do we do this?
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1answer
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Luminosity of Neowise

So, I have been trying to figure out the bolometric luminosity of the comet C/2020 F3 (Neowise) on the 22nd of June, 2020. At that time, Neowise was $1.4$ AU away from Earth and had an apparent ...
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1answer
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What complementary observation campaigns have looked at Kepler's field of view?

It seems to be common practice to double up observations. For example, shortly before New Horizons flew by Pluto, several of its moons were discovered by telescopes as a concerted effort was put in ...
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1answer
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Can New Horizons be used to measure the distance to Betelgeuse (despite its fickle photocenter)?

The New Horizons spacecraft is almost 50 AU from Earth and near-simultaneous images taken by its telescope and one on Earth have demonstrated parallax without relying on the movement of Earth in it's ...
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How did Michelson measure the diameters of jupiter's moons using optical interferometry?

In Betelgeuse: How its Diameter was measured (Chant, C. A., Journal of the Royal Astronomical Society of Canada, Vol. 15, p.133, Bibliographic Code: 1921JRASC..15..133C) the author says: The paper in ...
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2answers
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Is the Object in this Photo Mars?

A little bit of context: I dabble in amateur astronomy, however only very lightly. I originally wanted to make some observations of Mars because I know it is supposed to be very close these days but ...
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3answers
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Why haven't I seen the Moon?

It has been some time since I've seen the Moon. What are the conditions that might affect whether or not the Moon is visible within a 24-hour period? Please take into consideration any notable ...
6
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1answer
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If an object 1 billion light years away emits light, does it take more than 1 billion years to reach us because of the expansion of the universe?

From page 7 of the recent (September 26, 2020) edition of Science News Magazine: Detected May 21, 2019, the gravitational waves came from a source about 17 billion light-years from Earth, making this ...
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Limit Magnitude divide 2 arcsec

How can I derive limit magnitude in 5sigma/2arcsec ? I have the limit magnitude in 5sigma which derive from the magnitude with SNR reach 5. But I can not understand what the meaning of dividing ...
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What is this 3D graph on velocity dispersions of galaxies showing, exactly?

I don't fully understand these 3-dimensional graphs sometimes.... Why do the x-axis and the y show the same thing? Why do the horizontal axes run into the negative numbers? I've seen this on other ...
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How far have stars been seen beyond the center of the Milky Way?

What lies near the center of the galaxy is of great interest and in recent times the motion of dozen(s) of stars at the center of our galaxy orbiting around Sgr A* have been measured in great detail. ...
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2answers
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How does one “use” the Pan-Starrs data?

I've seen that a large block of Pan-Starrs data has been released and is available on-line and how the distributors of the data expect professionals and the general public to use the data in their ...
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2answers
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How far away are objects whose light will never reach us, because of the expansion of the universe?

I thought I had read this question on Stack Exchange before, but now I cannot find it... In fact, I thought I had posted this question before, somewhere, on Stack Exchange... I believe the answer ...
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1answer
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What measurements helped us in understanding 'Oumuamua's location and speed?

What measurements helped scientists understand 'Oumuamua's location and speed? I wanted to know how it was achieved and with what accuracy if possible.
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1answer
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What instruments are used to measure the distance to the Sun?

In the 18th century, the distance to the Sun was measured using the transits of Venus. Nowadays, the timing of radar pulses is used to measure the distance of things in our solar system. What ...
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1answer
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Determining needed exposure time given SNR

I need help on how to estimate an exposure time for a desirable signal to noise ratio (SNR). For example, given the magnitude and a desired SNR of a star we want to achieve, how long should the ...
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1answer
54 views

Is the LSST (Vera C. Rubin) telescope going to change position every 20 or 35 seconds?

This is a very particular question, I realize, but I am still curious... The Vera Rubin telescope is supposed to take a 15-second exposure, then take 5 seconds to move to its next spot... But I also ...
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1answer
254 views

Is this a Black Hole?

While researching about galaxies in Google sky, I came upon a strange area. Co-ordinates: 11h 6m 15.0 seconds | -77° 22' 9.8" A lot of space around this body is empty, is it possible that the ...
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1answer
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Technique for folding sparse event data in order to detect an underlying periodicity?

@JamesK's answer to When will the next transit of Earth be visible from Mars? Was the last one really on May 11, 1984? lists dates of 18 transits which I've converted to days since 1500-Jan-01 as <...
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I've seen something Incredible in the sky and really need help identifying what it is! [closed]

It was about 4 A.M. in North Wales and I was getting bored of what ever I was doing so decided to look out the window. I really love looking at the stars but this time it was different. The sky seemed ...
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2answers
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What's still needed before we can observe orbits of exomoons thereby weighing exoplanets?

Comments below this answer to How do we weigh a planet? point out that we currently cannot (or at least have not) detect moons around exoplanets, much less measure the sizes and periods of their ...
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1answer
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Catalogue of black holes

Where can one find a reliable list of black holes that have been discovered/observed so far, directly or indirectly, along with their properties, like mass, spin, etc.?
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How was the mass of Venus determined?

The mass of Venus seems rather complicated to determine to me: Venus doesn't have any satellites, so you can't just apply Kepler's third law (like you would with Jupiter or Saturn for instance) to ...
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1answer
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Are the most distant known objects in the universe more than 14 billion light years away? [duplicate]

When I hear about the most distant objects in the universe, such as the recently discovered galaxy GN-z11, their distances are usually stated to be a little under 14 billion light years away.... But, ...
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1answer
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What do 5-sigma, r, and lowercase-delta mean in the physical descriptions of major telescopes?

The typical 5σ point-source depth in a single visit in r will be ∼24.5 (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be ...
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How can Mercury's sodium tail be imaged?

I recently learned that Mercury has a sodium tail. Can this sodium tail be imaged with a ground based telescope? Is so, what is the minimum setup required to be able to take a picture of it? Do you ...
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1answer
62 views

How to isolate H$_\alpha$ from Nitrogen doublet emission lines

I am trying to find out line intensity and FWHM of H$_\alpha$6565 emission line from a quasar spectrum obtained from SDSS DR-14Q. Visual inspection of spectrum shows H$_\alpha$ being contaminated with ...
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1answer
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Magellanic Clouds

The Magellanic clouds do not seem to move much relative to the other background stars, which of course move a good deal. Is there some explanation for this or am I observing poorly?
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2answers
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What was the field of view of the Ohio State University Radio Observatory of Wow! signal fame?

This answer to Did comets 266P/Christensen or P/2008 Y2 (Gibbs) cause the Wow! signal? points out that the comets in question were nowhere near where the radio telescope was pointed. Wikipedia says ...
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1answer
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How is spectroscopy used to deduce what an object is made of?

Spectroscopy is an analysis of light (or other EM wavelengths) that is often used by scientists to examine what an object is made from or contains. Apologies if this is a stupid question, but this ...
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Is the Universe infinite? [duplicate]

https://en.wikipedia.org/wiki/Universe Is the Universe infinite or finite ?
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1answer
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How is it possible that we haven't discovered anything in the Oort cloud yet?

The Oort cloud is a hypothetical cloud of small icy bodies surrounding the Sun at more than 1000 AU. It is thought to be a vast reservoir of comets that occasionally get disrupted, sending comets ...
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1answer
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When was the diameter of Titan first measured?

Titan is enshrouded in a thick opaque cloud of methane : with a telescope, you can't see the moon's surface. Because of this, from a distance, you can only see the diameter of the moon + its ...
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1answer
381 views

What does “unremarkable transverse peculiar velocity” mean exactly, and how is it calculated here?

The abstract of A magnetar parallax (also in MNRAS) contains the following: Combining our new observations with two archival observations from 2006, we have refined the proper motion and reference ...
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How are small objects automatically identified and their locations determined in digital images?

I have a large quantity of old digital images of low energy electron diffraction (LEED) patterns that I must process to identify and locate small, sometimes elongated gaussian-like blobs of a few ...
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1answer
105 views

Is a literal instance of Russell's teapot possible?

Much has been said about Russell's teapot, and I accept as obvious that a teapot would be too small to be detectable in an orbit around the Sun by any reasonable method today, or by any method that ...
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Satellites in a row [duplicate]

I often watch the night sky in central North Dakota and love seeing satellites zooming by. Recently I saw a string of satellites traveling SW to NE. There were as many as 30 traveling one after the ...
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2answers
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Why does this large Newtonian telescope's front cover have two or three holes in it?

The Michael Bernardo video How to use an Equatorial Mount for Beginners shows a large Newtonian telescope on an equatorial mount. The cover of the telescope's large aperture shows what looks like ...

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