Questions tagged [observational-astronomy]

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

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13
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1answer
639 views

How is the Hubble constant determined from gravitational waves?

We know there is a discrepancy between measurements of the Hubble constant, $H_0$. On one side there is the method of the Planck mission, where they use the CMB and the $\Lambda$CDM model to determine ...
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2answers
225 views

What will it finally take to accurately measure the distance to Betelgeuse?

Comments below What is the maximum distance measurable with parallax? discuss challenges associated with parallax measurements of Betelgeuse and link to Wikipedia’s Betelgeuse; Distance measurements ...
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1answer
44 views

What equipment and techniques were used to study Betelgeuse's diameter in 1920?

Comments below What is the maximum distance measurable with parallax? discuss challenges associated with parallax measurements of Betelgeuse and link to Wikipedia’s Betelgeuse; Distance measurements ...
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1answer
48 views

Flux density from brightness map

This is a naive question. I have a temperature map of radio emission at 1420 MHz, in Kelvin. I want to extract the flux density (in Janskys) from an extended region of this map. Is the flux density ($...
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0answers
32 views

Ladakh India where the moon (Ramadan moon) is sighted but not in rest of India [duplicate]

Today 22 May 2020 around 3 p.m Ladakh India sighted new moon(Ramadan moon) but not in rest of India.I read many articles acc. To them it is not visible today, then how it was seen from Ladakh... .
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1answer
72 views

Why is SWAN dimming?

The SWAN C/2020 F8 comet is passing near the Earth, but from Wikipedia The comet has dimmed a small amount since May 3. It was expected to possibly reach 3rd magnitude in May, but is now ...
2
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0answers
30 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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0answers
44 views

Longest time after an image was taken when a new solar system body was discovered from it?

This answer to If there's nothing special about Pluto, why was it discovered so early? says: In fact, often objects are discovered to be in pictures from long ago, such as Orcus, discovered in 2004,...
-2
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1answer
91 views

What are the necessary steps required for calculating the size of a star? [closed]

Title pretty much says it all. Basically, what exact variables are used, and what steps need to be taken, in the calculation of the size of a star? Preferably, some example data for how a the size of ...
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0answers
42 views

How does the Astronomical Twilight depend on the night length or the day length?

Some references say that the Astronomical Twilight starts at the last 1/8th of the night length, so it is long in Winter and short in Summer; But by using the 18 angle (sun elevation below the ...
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2answers
956 views

Are there neutron stars whose magnetic axis and rotating axis are the same, and if so what will happen?

I know that there's probably a higher chance of having a neutron star that has its magnetic axis inclined to the rotational axis rather than having it perfectly aligned. If they are not aligned, the ...
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1answer
36 views

Options for observational astronomy [closed]

For getting into a PhD program for observational astronomy, is physics major and data science minor enough?
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3answers
2k views

What is the probability of seeing a neutron star as a pulsar?

Pulsars are neutron stars that emit a beam of electromagnetic radiation that is not aligned with its rotation axis. If the Earth passes through that beam of radiation, we see a pulsar. Pulsars are ...
2
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1answer
114 views

What's the highest frequency that's been imaged by a radio telescope?

In this answer to Should we update definitions and remove the 100 GHz hard limits on radio astronomy related tags? I wrote the following partial answer: Yes, there are plenty of dishes that focus ...
1
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1answer
52 views

Is there any way to seperate astronomical and instrumental objects?

Here is a image of hcg79 taken from APO. I'm just curious if there is any way to seperate astronomical and instrumental features in this picture? Thank you.
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1answer
54 views

How is Cosmic Microwave Background's temperature measured?

How do Cosmic Microwave Background missions/telescopes measure CMB temperatures? I understand that CMB has Planck's spectrum. So I was thinking one strategy could be to measure the spectral radiance ...
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16 views

How to select galaxy emitters from color-color diagram? (Those candidates which are above a line in a plot)

I am trying to select the OII emitters from the colour-colour diagram of galaxies data. I don't know how to select those candidates which are above the line. Here is my colour-colour diagram. . What I ...
0
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1answer
45 views

How does diffraction occur in a reflecting telescope?

It's understandable how diffraction occurs in refracting telescopes, because the lens itself is a small aperture for light to pass through. But what about reflecting telescopes? Since light is ...
4
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4answers
297 views

How do focal length, angular magnification and field of view relate?

The larger the focal length the larger the angular magnification The smaller the focal length the larger the field of view. I don't understand why this applies. I'm talking specifically about ...
2
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2answers
78 views

Why are Cassegrain telescopes shorter than Newtonian reflecting telescopes?

Many websites say this is because the effective focal length of the objective is increased by making the secondary mirror convex. This allows a Cassegrain telescope to be shorter than a similarly ...
3
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1answer
30 views

Brightness, altitude & azimuth for satellites?

I'm using the heavens-above website to identify a satellite I've seen several nights this week. The question is related to how I can search the satellites table with the information I can provide. ...
0
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1answer
75 views

Can the interferometer called “Gravity” measure “a few centimeters on the Moon”?

Phys.org's Very Large Telescope sees star dance around supermassive black hole, proves Einstein right links to several ESO videos, including Interview with Reinhard Genzel (in English). After ...
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1answer
96 views

How low can the sun be seen in the sky?

I'm interested in knowing how low the sun could ever get in the sky and still be seen. More technically: what's the minimum possible elevation of the sun at which it can still be seen above the ...
2
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0answers
18 views

Detect sources near image edge with python photutils

As my question suggests, I 'm trying to use a python library photutils in order to detect sources from MUSE cube. MUSE (Multi Unit Spectroscopic Explorer) is an ...
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1answer
31 views

Calculating Field of View of a Telescope Given Time of Another Object

Given the celestial coordinates of a certain star and the time it takes to pass across your telescope's eyepiece, how can you calculate the field of view of the telescope?
0
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1answer
30 views

Distance to star using color index

I'm doing the following question: A star is observed with UBV magnitudes $m_u = 16.31$, $m_b = 14.52$, $m_v = 13.76$. Spectral analysis gives $M_{bol} = 7.31$, $BC = -1.02$, $(U − B)_0 = 1.222$. ...
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24 views

What is the highest redshift a galaxy with a known stellar mass can be observed?

As part of my research, I would need the following information which it seems I cannot find it in literature. I would like to know what are the highest redshifts at which $10^{7}$, $10^{8}$, and $10^{...
2
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0answers
26 views

Moving objects in the sky tonight 27th March 2020 [duplicate]

Multiple moving objects not in a line. The are staggered single line and in groups of two or three. One or two moved downward. They had a dim light orangey colour. It was not obvious that these ...
2
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0answers
131 views

Betelgeuse problem

I've been given this problem: (a) A telescope is required to image an area of the sky of angular size 1 arc second onto a 10 mm square CCD. What focal length must the telescope mirror have to fully ...
15
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2answers
3k views

Has radio astronomy ever been done on objects that appear very close to the Moon? Is this avoided?

This answer to Which kinds of astronomical observations most need to avoid the Moon being up? mentions For completeness - radio, mid-infrared and mm-wave observations are unaffected (unless the ...
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Why were solar constant measurements before TSIS-1 all about 0.3% high?

Phys.org's Solar energy tracker powers down after 17 years says: "The big surprise with TSI was that the amount of irradiance it measured was 4.6 watts per square meter less than what was expected,"...
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Was the “green star” event in NGC 3314 ever figured out or named?

from NGC 3314 Variable Object by By Bill Keel (University of Alabama, Tuscaloosa) and Lisa Frattare (Hubble Heritage Project, STScI). The object in question is circled. Comments below this answer led ...
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1answer
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Can I use the parallax coefficients for observatories as a proxy for latitude using arctan2(sin, cos)?

In How are the three character IAU Minor Planet Center's Observatory Codes assigned? Why are some letters so popular? I looked at the distribution of the first alphanumeric character versus the value ...
3
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1answer
54 views

Visible satellites real time position API

I'm trying to obtain the azimuth and elevation of all (or at least the majority) visible artificial satellites from a given latitude and longitude. Is there a quite stable API that does that for free? ...
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1answer
57 views

How are the three character IAU Minor Planet Center's Observatory Codes assigned? Why are some letters so popular?

Answers to Latitude, longitude and altitude of Ckoirama Observatory; where can things like this be looked-up? point to https://www.minorplanetcenter.net/iau/lists/ObsCodesF.html which currently lists ...
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4answers
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Latitude, longitude and altitude of Ckoirama Observatory; where can things like this be looked-up?

This answer to Is Starlink 1130 (Darksat) really dimmer? links to the March 16, 2020 paper in arXiv First observations and magnitude measurement of SpaceX's Darksat which finds only a modest decrease ...
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2answers
3k views

Which of the planets would be detected if they were exoplanets?

An (almost-)omnipotent being selects the solar system, presses Ctrl+C, and then Ctrl+V several times, creating copies at distances of 5, 500, 50.000, and 5.000.000 light-years away. All in a direction ...
1
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1answer
57 views

How to find Kepler/TESS data [duplicate]

I have some basic understanding of the Kepler/TESS mission. The missions both look at the stars and try to find the dip in the light from the stars to find possible existence of exoplanets (exomoons ...
3
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2answers
126 views

Which kinds of astronomical observations most need to avoid the Moon being up?

This comment to Did nobody in the Astronomy community think 12,000 new satellites in LEO might be a problem? links to Phys.org's New ESO study evaluates impact of satellite constellations on ...
13
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1answer
945 views

How is an exoplanet characterised as “Earth-Like”?

Which features or characteristics are taken into account to characterize an exoplanet as "Earth-Like"?
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1answer
83 views

Usefulness of the hour angle (HA)

The Hour Angle (HA) is measured west from the observer's meridian in hours, mins, seconds. How is the Hour Angle used to help plan observations during the night at a telescope?
2
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1answer
51 views

Continuum at 230 GHz

what does it mean 'The observations were made in the CO J=2–1 line and continuum at 230 GHz (1.3 mm)'? "The observations of the continuum were also made with a bandwidth of 320 MHz. " http://articles....
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54 views

Is 486958 Arrokoth (2014 MU69 aka Ultima Thule) the only object determined to be binary by occultation?

The asteroid 486958 Arrokoth was discovered to be binary by astronomers lugging a bunch of telescopes around (I think) camping with them. The timing offered additional astrometry for the orbit ...
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26 views

What are Stokes parameters for galaxy shapes, how do they compare to Stokes parameters in optics?

I remember Stokes parameters as a way to completely define the polarization state of a well-defined beam of light. However several questions here refer to Stokes parameters used in characterizing the ...
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0answers
3 views

Do all High-Mass X-Ray Binaries have observable supernova remnants surrounding them?

I am studying high mass X-ray binaries, which are star systems that generally contain a neutron Star orbiting a larger companion. My assumption is that such systems began as two typical stars in ...
2
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1answer
104 views

Why does moon moves to side if I change my position directly into it?

I've setup this scenario on Stellarium where the moon is aligned with East direction. I wanted to see the change of altitude of the moon if I move straight into its direction (time of observation is ...
3
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1answer
38 views

What is a “21cm/mm absorption system” in the context of measuring old photons from quasars?

This answer links to Wikipedia's Time-variation of fundamental constants which cites Further Evidence for Cosmological Evolution of the Fine Structure Constant (J. K. Webb et al. 2001), the abstract ...
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0answers
43 views

Why do all the stars near this comet show up as four separate dots in a row?

After seeing this tweet about our not-so-new but at least newly-discovered "mini-moon" I scrolled down and saw the tweeted image below. Since the object is the known short-period comet 114P/Wiseman–...
0
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1answer
92 views

The goblin furthest [closed]

I just watched a documentary last night that stated a new discovery was so far away in our solar system the Hubble could only show it as a few blurred pixels, Robert Fosbury narrated and it was called ...
4
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1answer
406 views

Have there been studies of “old photons” to see just how constant things like Planck constant has been?

The question Are photons aged? and answers therein have got me thinking: I vaguely remember hearing something about experiments where "old photons" were collected by large telescopes from very ...

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