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Questions tagged [observational-astronomy]

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

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What causes random irregularities in the earth's rotation accounted for by dynamical time

I read in a book that the earth's rotation sometimes shows unpredictable irregularities(not caused by precession, nutation, tidal forces) which are accounted for using dynamical time. What would be ...
2
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1answer
98 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 there a possibility that ...
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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
75 views

Is it possible to see a spacecraft orbiting the moon with a pair of binoculars?

On this clear early morning over London, I was studying the moon with a pair of binoculars and noticed a tiny dot of light that appeared to trace a slow orbit around the moon. I reckon it moved ...
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3answers
156 views

How do we know distant stars still exist

The Pleiades are 450 light years away. Thus when we see the twinkle in the night sky the light that hits our retina emanates from the year 1569 or so. On that proviso; how can we be sure that the star ...
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976 views

How can gravitational lensing makes a quasar appear brighter?

How can gravitational lensing makes a quasar brighter than it would in the absence of a foreground galaxy?
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Cases of gravitational lensing resulting in a recognizable image of an extended object?

There are several different classifications of gravitational lensing phenomenon. Here I am asking for any examples of strong lensing where the lensed image of an extended object is magnified and ...
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1answer
48 views

Circumpolar Equation Derivation

Edit: Geometric answer from Math.stackexchange I am trying to understand where the circumpolar equation comes from. $\delta \geq \frac{\pi}{2} - l$ I can understand that the sort of "rotation" of ...
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1answer
38 views

Meteor shower shooting stars

Shooting stars are actually meteors falling down on the surface of earth. How come some of them appear shooting up and not down?
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Jupiter-Venus conjunction is vertically aligned. I'm at 49° N. How is this possible?

The very beautiful Jupiter Venus conjunction of ~ 2019-01-20 (practically something out of "2001 A Space Odyssey") is seen as "vertically aligned" in the dawn sky, Venus "above" Jupiter. See this ...
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1answer
46 views

Simulating Noise in Astronomical Images

I want to add realistic noise to a simulated image but I am a little confused about the process. I want to have some Gaussian random noise representing the readout noise and to also add Poisson noise ...
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0answers
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How far away was the binary black hole that produced GW170729?

GW170729 was gravitational wave signal's detected by the Virgo and LIGO detectors. I read the following in a news report: Known as GW170729, in accordance with the date of its discovery (in US ...
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1answer
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What is the dimensions of the smallest object detectable by an optical fiber from a specific distance?

Optical fibers are well-known to observe astronomical objects, say, galaxies, to generate massive spectroscopic surveys. The galaxies are often very far from the optical fibers of a telescope. However,...
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67 views

76mm reflector vs 70mm refractor? Both are at sale at $200

I'm starting my astronomy hobby and looking for a beginner telescopes to start with. I've searched couple websites and found these 2 within my budget. I know for a fact that refractors gives you ...
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2answers
70 views

When astronomers “look into the past” are they accounting for the expansion of space?

Every time astronomers look "13 billion" years into the past, not only is there more space than there normally would be at that instant which increases from observation to observation, but there was ...
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3answers
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Advice on first Telescope (refractor vs reflector), Barlow lens

I am planning on buying my first telescope. I am getting an 80mm refractor and a 114mm reflector for the same price range. Which would be a better option? Further, would a Barlow lens solve the ...
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1answer
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How are exoplanets with 10,000 day periods discovered with the radial velocity method?

The radial velocity technique has apparently been used to discover exoplanets with extremely long orbital periods of ~10,000 days. For example, see this link: https://exoplanetarchive.ipac.caltech....
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What area of Proxima Centauri would need to be occluded for the effect to be observable on Earth?

One of ideas of how Breakthrough Starshot could communicate data from Proxima Centauri is to have a massive swarm of the solar sail powered craft to pivot (with their sails) synchronously, taking ...
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1answer
81 views

What would the night sky look like from a planet at the centre of a ring galaxy?

If there were an observer on a planet in the centre of a ring galaxy (omitting the galactic core) what could they expect to see in their night sky? I am currently under the impression that their night ...
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1answer
61 views

Can we learn anything from observing galaxies edge-on, like the Spindle Galaxy?

I was reading about NGC 5866, sometimes referred to as the Spindle Galaxy. It's notable because of its inclination relative to Earth; we see the disk from the side, rather than face-on. The difference ...
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1answer
39 views

Impact of Atmospheric Water vapour on Optical Observations

I would like to ask; how does Water Vapour in the atmosphere interfere with astronomical observations? Is it in the same manner as Carbon dioxide? What brought this to mind is the following: A ...
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Why do default coordinates from IR-optical observatories are usually not trustworthy, while from radio interferometers they usually are?

I have noticed in my experience that the coordinate solution within the headers of default reduced images from radio interferometers are commonly trustworthy to the arcsecond or less. From IR and ...
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52 views

Distance between two planets [closed]

Planet A and Planet B orbit a sun-like star. Planet A has a semi-major axis of 1 AU from the star. Planet B has an albedo of .8 and has the same radius as Jupiter. When Planet B is observed from ...
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1answer
132 views

Estimates for “undetectable” planets in extra-solar systems

As far as I've been able to determine, it appears there are some significant limitations on our ability to detect exo-planets that are below certain sizes or beyond certain distances from their stars....
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2answers
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Why do we use filters in telescopes for astronomical imaging?

I have read that if we image without a filter we get no information about the color or SED of objects. Can anyone elaborate the reasons for using filters for imaging/photometry? What happens if we ...
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After Oumuamua passage, has an “urgency” telescope time request procedure been set up?

During the rapid passing of ʻOumuamua through our solar system, it was difficult to get instant telescope time. Usually, formal requests and a review process are necessary before telescope time is ...
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3answers
287 views

Why do stars twinkle but planets don't [duplicate]

Many people say that stars twinkle because of Earth's atmosphere. However, the atmosphere is still there when we look at planets and don't see they twinkling. Is there a clear scientific consensual ...
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1answer
2k views

What is it exactly about these flares of infrared light from Sgr A* that “confirms” it is a supermassive black hole?

CNET.com's SCI-TECH Scientists confirm a 'supermassive black hole' at the heart of our galaxy It's "mind-boggling", they say. This links to Astronomy.com's Scientists finally confirm the Milky Way ...
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6answers
7k views

Puzzling quotes from astronauts about earth size

I have no doubt that we have been to the moon. This question has nothing to do with a moon landing hoax. But, there are two quotes from two different astronauts regarding the size of the earth as ...
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1answer
52 views

How to convert quasar flux time series from observed frame to rest frame?

I have flux time series of quasars in the observed frame and want to convert it in the rest or quasar frame. Any one who can help? Thanks
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0answers
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My family saw small dots in the sky moving rapidly at night [duplicate]

My family and I saw small dots moving rapidly from north to south that flew in a V formation (the kind that ducks fly in). There aren't any ducks in my country. This phenomenon appeared twice. They're ...
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1answer
68 views

How far can a planet with living beings get before we cannot see the living beings? [duplicate]

Let there be a planet with Earth-like life. However, no trash or monuments or other visible structures, just organisms. How far can that planet be from Earth before our equipment just cannot observe ...
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66 views

Solar series 142 and 147 started same year - series 147 and 152 will be ending same year. Why? Coincidence?

This question was left over from the last question I had, so I am asking it separately here: I have been looking into two solar eclipses (Saros series 147 and 152) that will both be occurring in 2021....
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Why the blank wedges in this very early 21 cm map of the Milky Way? (Oort et al. 1958)

Jan Oort was a pioneer in radio astronomy. Wikipedia says: It has been written that “Oort was probably the first astronomer to realize the importance” of radio astronomy. “In the days before radio ...
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1answer
57 views

What is a “semester series” for eclipse prediction? - Solar saros series 147 and 152

Yet again, I just stumbled across another baffling eclipse question (actually, two now). I was interested in two eclipses (Saros series 147 and 152) that will both be occurring in 2021. Each of these ...
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0answers
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How to compare the observation with the theoretically predicted result?

On the Wikipedia Article on “Geodesics in general relativity”, it says the following: “Thus, for example, the path of a planet orbiting a star is the projection of a geodesic of the curved 4-D ...
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How was calculating the celestial latitude using an astrolable of any help to sailors?

I'm sorry if this sounds like a silly question but I don't understand how measuring the location of a star would help in sea navigation.
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2answers
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Planning observation: determine dates where moon is within 30 degrees of my object?

I'm planning an observation for a proposal and I need to determine which dates the moon is within 30 degrees of an object so I can ask to not be scheduled for those dates. This object is near the ...
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1answer
48 views

Throughout the year, are all parts of the night sky visible from any given point on Earth?

Or are there points on Earth where certain parts of the 360° night sky are never visible throughout the whole year? Depending on the answer to this question, are there points on Earth where parts ...
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2answers
87 views

How to calculate exact angle to the moon?

I am building some device as a gift for my girlfriend. For this device to work, I need to be able to calculate the angle to which I should look towards (3D angle), in order to see the moon. This ...
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1answer
86 views

What is Propeller Effect exactly?

I find the original reference seems to be here. I still do not understand the mechanism. It is necessarily occur in neutron binaries? Anyone can introduce it in detail? This paper is old.
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1answer
136 views

What would stargazing be like at the edge of our galaxy?

Let's say, for the sake of speculation, we acquire the technology necessary to travel to the outer edge of one of the spiral arms of our galaxy. We go to a star in this "outer rim" and land on a ...
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1answer
220 views

What phenomenon causes “lunar waves”?

In multiple video clips of the moon but also one of Jupiter, some kind of waves can be observed. Is this just the effect of the object moving behind layers of different refractive indexes (similar to ...
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2answers
54 views

Do we observe Mars Eclipse or Jupiter Eclipse?

We frequently observe lunar eclipse throughout the year. Have we ever observed Mars Eclipse or Jupiter Eclipse or Saturn eclipse?
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172 views

Eyepiece diameter for small focal length planetary viewing on a large dobsonian?

I have a 12" dobsonian with a 1500mm focal length and want to do some higher magnification planetary viewing. Currently my highest magnification is ~80x via my 19mm eyepiece (calculated here), but I ...
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3answers
53 views

Ratios of magnitudes instead of differences

The color index in the photometric system is defined by the differences in magnitudes between two wavelength filters, which gives the ratio of intensities. For example, to determine the B-V index, you'...
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49 views

What are the procedures and protocols to use with Gauss'method and personal observations?

I would like to use the Gauss' method to determine the orbit of planets of solar system. I would like to calculate their orbits with personal observations. What is the methodology/procedure/protocol ...
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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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1answer
365 views

Why is H_delta prominent in type A stars?

I understand factually that H$\delta$ lines are most prominent in type A stars and less so in more extreme types of stars on the H-R diagram. However I was wondering the reason for why they are not ...
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1answer
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The systematic review of past observations in the hope of finding things that may have been missed

I seem to remember a TV science programme which re-examined the slides that led to the discovery of Pluto and then took a fresh look at earlier slides taken of the space which Pluto was passing ...