Questions tagged [observational-astronomy]

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

155 questions with no upvoted or accepted answers
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160 views

How do radio astronomers avoid having their receivers burned out by ground-imaging radar from satellites?

After about 34:00 in the 9th press conference of AAS 235, radio astronomer and NRAO's spectrum manager Harvey Liszt talks about Radio Astronomy in a New Era of ...
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Determining wind speed distribution on Mars using dune shapes?

As a fan of exometeorology (the study of atmospheres of other planets), I scanned through a whitepaper Measuring Mars Atmospheric Winds from Orbit which says Measurements of Mars atmospheric winds ...
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Is the discovery of a “mass gap” black hole by this tiny telescope just plain luck/serendipity or could it be the first of many similar discoveries?

The Kilodegree Extremely Little Telescope is a pair of modest lenses with high quality medium format CCDs attached sitting on oversized mounts in Arizona and Sutherland. These very modest instruments ...
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What's the largest angle that light has been “seen to bend” by gravity? (of one object by a separate object)

Gravitational lensing is everywhere! because it falls off so slowly with $r$: $$\Delta \phi \approx \frac{4GM}{c^2r_0}.$$ That's the first order term. For a nice derivation see Viktor Toth's The ...
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How was the axial tilt of planets measured?

https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ? I guess it's "easy&...
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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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Are occultation observations used/useful for orbit determination?

The IAU Minor Planet Center lists $(486958)\space 2014 \space MU_{69}$ "Ultima Thule" as having an uncertainty parameter of 2, based on the observation arc of 851 days, from its discovery in 2014, to ...
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1answer
287 views

Could non-supernova carbon, oxygen, or silicon flashes be observed?

I was reading about the helium flash, the short but sudden onset of helium fusion in certain red giant stars. As I understand, the upper (nondegenerate) layers of the star absorb the energy as they ...
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A new (radio) neutrino telescope in Greenland?

I just stumbled upon ScienceMag news from July 14th, 2021 which says: By placing hundreds of radio antennas on the ice surface and dozens of meters below it, they hope to trap elusive particles known ...
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What about the U planet?

In 2014 and 15, an object called U has been detected by the ALMA in Chile, considered likely to be a super-Earth at 300 AU, among other options. Is it located where the hypothetical super-Earth ...
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What capabilities of Hubble are unique and irreplaceable? What can it do that simply can't be done by any other ground or space-based telescope?

It's impossible to summarize in an SE post the depth and breadth of the contributions to science made using the Hubble Space Telescope. Above the atmosphere it has access to an extremely dark and ...
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Significantly blueshifted Lyman-$\alpha$

Lyman-$\alpha$ line in galaxies is notably known to show a double peaked profile, mainly due to its scattering in a moving medium, see e.g., the very recent Matthee et al. 2021, The X-SHOOTER Lyman-α ...
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What exactly would the resolution of an exoplanet hypothetically imaged by using the Sun as a gravitational lens be?

This video talks about how by sending a spacecraft to around 600 AU and beyond, we would could use the Sun as a gravitational lens and take clear detailed images of exoplanets light-years away. What ...
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From what distance could the Sun's planetary nebula be seen entirely with free eye?

When collapsing to a white dwarf, a red giant Sun would emit a planetary nebula. How far from the Sun would that nebula stretch at most? Also: At about what distance could you see the planetary nebula ...
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Is it possible to use something besides emulsion to directly record the image of a nighttime object using a telescope?

The following questions have got me thinking. Is it possible to use Photolithography for telescope image sensor? Fresnel lenses for a makeshift Galilei telescope? Has anyone ever tried to make a ...
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K-correction vs resizing photometric bands

Is there a difference between a K-correction (see Wiki https://en.wikipedia.org/wiki/K_correction) and simply "resizing" the bands, e.g. the 2-10 keV x-ray band, with the redshift? I've read ...
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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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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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How do magnetic fields mess with astronomers' observations?

Does anyone else watch 'Dr. Becky' on YouTube? Her March 'Night Sky News' video, subtitled 'The biggest black hole burp, a wobbly Milky Way & Betelgeuse is brighter' says that... "Dust and ...
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What actually determines the angular uncertainty of the source of a detected gravitational wave?

This answer and comments got me thinking. Astrometry 101 tells us that while we can use $\lambda/D$ as an estimator of resolution, if we can assume a point source we can determine the centroid or ...
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In the JPL small body browser, why is uncertainty on absolute magnitude “N/A”?

In the JPL small body browser, orbital elements are all provided with uncertainties and even a covariance matrix, such as for 2013 LA2. Very good. But underneath, the absolute magnitude is reported ...
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Infrared telescopes, magnitude and observations

Currently 22-23 magnitude could be the limit to make a spectrum for ground based 10m class telescopes, 21-22 magnitude may be easy for them. 4m class telescopes could possibly handle 20 magnitude, I ...
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Estimate the shape of an object based on flux curve

Is there an aproximation to know the shape of a dust cloud,etc based on the magnitude/flux curves of stars they transit? Example, can I know if the shape is (at least in 2 dimensions) elliptical, ...
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51 views

Is it Possible to Calculate The Centre of Mass of the Visible Universe?

It is easy to deduce that we appear to be at the centre of the visible universe, assuming the visible universe is approximately isotropic and homogeneous in all its properties, including expansion ...
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Flickering and noise

I'm working with flickering measures from some stars. So, I take differential magnitudes, make a histogram and fit their standard deviation. My measure of flickering is the FWHM (full width at half ...
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54 views

New method for exoplanet detection?

Could it be possible to detect exoplanets that have an abundance of iridescent minerals by analyzing their star's spectra over time as the angle in observation would lead to changes in absorbed ...
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How often are electron-multiplying CCDs used in telescope focal planes? Will Nancy Grace Roman be the first use in a space telescope?

Section I. of The Wide Field Infrared Survey Telescope: 100 Hubbles for the 2020s says: Table 1 summarizes the WFIRST instrument suite, and Figure 1 presents the effective area of the Wide Field ...
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Salary of observatory worker?

I am thinking of becoming an astronomer becuase I love looking through my telescope at night, and may want to make it my profession. Is there money to be made working at an observatory, or is the BLS ...
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50 views

Hello again, Barlow Lenses

I am debating if I should buy a 2x Barlow Lens. My telescope, a go-to Meade star navigator, has an aperture of 114mm, focal length of 1000mm and I currently have a 9 and 26mm eyepieces. I want to see ...
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1answer
223 views

Precision in the measurement of the distance to the Sun

How precisely can the distance to the Sun be measured? Wikipedia says the distance to the Moon can be measured upto millimeter precision. But Wikipedia article on distance to the Sun says only about ...
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53 views

Short term changes in celestial coordinates of stars

The right ascension and declination of stars change on a day to day basis. Some of the changes are quite large. The right ascension of Polaris, for example, changes by more than a degree over the ...
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Are Saros series separated by “40” in numbering related in any way?

Can anyone help with this question? My question arose from an eclipse related observation that I made while looking into lunar Saros series 129. It is the Saros series number for the lunar eclipse ...
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72 views

Creating planispheres from the perspective of nearby objects

I'm attempting to create a set of [reasonably] astronomically accurate planispheres from the perspective of observers positioned at the north or south poles of various nearby celestial objects. So ...
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49 views

In SETI has anyone calculated an estimate of the mean time between observations?

So the Drake Equation, proposed by Frank Drake, is often cited as a means to estimate the number of intelligent civilizations that exist in the observable universe. Initial calculations by Drake ...
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Linear motion in the equatorial frame

I would like to calculate how the RA/Dec changes when an object has an apparent linear motionin the equatorial sphere. For example, more or less what an artificial satellite would do in a circular ...
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Why does X-shooter use double passes through prisms for Echelle cross-dispersion instead of gratings?

The catchy title Down-the-barrel observations of a multiphase quasar outflow at high redshift: VLT/X-shooter spectroscopy of the proximate molecular absorber at z=2.631 towards SDSS J001514+184212 ...
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Could we detect a globular cluster consisting entirely of black holes?

A paper recently came out in Nature simulating the evolution of the $\sim10^4M_{\odot}$ globular cluster Palomar 4 (Gieles et al. 2021, arXiv link). The authors argue that in ~1 billion years, a ...
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Explain as simply as possible how the Sunyaev-Zeldovich (SZ) effect is used to estimate the Hubble constant

The Sunyaev–Zeldovich effect (SZ effect) is useful in determining the Hubble constant because it is independent of the cosmic distance ladder. This effect occurs when CMB (cosmic microwave background) ...
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Would a possible accretion disk around a primordial black hole 500 au from the Sun be visible in present telescopes?

If the hypothetical two-inch black hole 500 au from the Sun had an accretion disk, might current telescopes detect it already or do we have to wait till the Vera Rubin Observatory starts work?
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How to calculate rest-frame luminosity in a specific wavelength band?

For instance, I have a set of templates whose y is in Jy and x is in Angstroms. I have both of their rest-frame and obs-frame wavelength (i.e. redshift). I want to know their luminosity in one ...
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Logarithmic rebinning and continuum removal of stellar spectra

I am trying to learn how to derive the line of sight velocity distributions from galaxy spectrum to extract kinematical parameters like rotational velocity and velocity dispersion. Therefore I need to ...
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How can the CMB have a “monopole anisotropy”?

Wikipedia's Cosmic Microwave Background (CMBR) radiation monopole anisotropy (ℓ = 0) says When ℓ = 0, the ${\displaystyle Y(\theta ,\varphi )}{\displaystyle Y(\theta ,\varphi )}$ term reduced to 1, ...
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Is an “observation campaign” well recognized thing in Astronomy? Is it self-declared? Are there standard ways to announce or coordinate?

The Astronomy meta question Should we have an observation-campaign tag and what is good usage advice for it? lists about 13 example questions where the tag might apply. There are several answers that ...
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Is there a collection or list of all planned observations of 99942 Apophis during its 2021 close pass to Earth?

For example, I found Goldstone Radar Observations Planning: 99942 Apophis in 2021 and 99942 Apophis 2021; Planned, Scheduled and Completed Observations at lawn.com? which seems empty. But I'll bet the ...
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Can the lensing effect of Sagittarius A* be used to image the stars diametrically opposite to the sun?

The sun can magnify an image of a source 100 ly away nearly 100 billion times, if the ring is captured from the nearest focal point (550AU). According to Christian Ready of Launch Pad Astronomy, we ...
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Convert Object Intensity to Pixel Intensity

If I have an object of some size and spectral radiance, and it's some distance R from a camera, how would I calculate its digital count value in an image? I'm sure there's an equation out there, but I ...
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Heat map of portion of the sky visible for a given observatory on Earth?

Reading Calculating area of visible sky I started wondering which portion of the sky one could observe how long given the 3D coordinates of an observatory, and two points in time. In other words, I ...
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What does a narrow-band “point spread function” look like for long exposures from the VLT's large interferometric aperture?

In interferometric radio astronomy UV plots are the first step in understanding what a point spread function (PSF) will look like for a given location in the sky observed over a period of time. The ...
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What are recent discoveries with Earth-based radar telescopes?

The Wikipedia article on radar astronomy lists a few important discoveries using radar technology in general, i.e. also using space-crafts: The following is a list of planetary bodies that have been ...
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29 views

Different approaches to quantify light pollution on a given location on Earth?

The question Light Pollution: what is the difference between artificial brightness and brightness and SQM made me wonder which different ways exist to directly and indirectly quantify light pollution ...