Questions tagged [observational-astronomy]

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

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Knowing location, LST, the amount & direction of displacement of an unknown star in a 2d image over time, can you calculate the coords of this star?

Basically I have camera, my location, my local sidereal time. I want to point the camera in one direction and shoot a timelapse of a certain star exactly in the middle of the camera view. So I know ...
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1 vote
0 answers
123 views

How to find the aFOV of a eyepiece?

How do I find the apparent field of view (aFOV) of a eyepiece using simple math (if possible)? I need the aFOV to give as a value to Stellarium’s custom eyepiece I found a Q&A about this subject ...
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7 votes
2 answers
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Will 3,600ft asteroid be visible at my location tonight?

According to NASA, a 1.1-kilometer asteroid called 7482 (1994 PC1) will be visible tonight at 5:50PM. How do I know if this asteroid will be visible at my location with the naked eye? When NASA says 5:...
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4 votes
2 answers
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How to interpret this spectrum of the "new DESI Quasar at z = 6.53"; what causes the big edge at about 9150 Angstroms?

I'm not exacty sure why but Scitech Daily's Seeing Dark Energy’s True Colors: DESI Creates Largest 3D Map of the Cosmos includes the graphic and caption below. It indicates a quasar in a Hubble image ...
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2 votes
1 answer
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How does IXPE measure polarization, and why does it have three identical X-ray telescopes?

From The Observatory: Anyone who missed any of the AAS 239 press conferences can see them on the AAS Press Office's YouTube channel! Here's the full program. From there I found the Monday, January ...
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2 votes
1 answer
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Next eyepiece for my telescope; how do decide which one to get?

I have an Astronomers Without Borders telescope with 650 mm focal length and 130 mm aperture. To go with them, I have a 10 mm and wide eye relief 25 mm eyepiece. I tried to view Jupiter with the 10 mm,...
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22 votes
2 answers
3k views

What ground-based observational evidence is there that the Moon doesn't have an atmosphere?

The Moon doesn't have any significant atmosphere (surface pressure is $3\times10^{-15}$ bar). Can the absence of atmosphere on the Moon be determined with ground-based observations? When was it first ...
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4 votes
1 answer
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Examples of the oldest "precoveries"; objects that were first discovered in recent data but then looking back are confirmed in much older data

Example from Ars Technica's Radio astronomers scouring the archives spotted black hole devouring a star: Astronomers found another TDE in 2020 (dubbed AT 2019qiz), which provided the first direct ...
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8 votes
2 answers
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Which JWST instrument modes are compatible with observations of the bright trans-Earth planets Mars, Jupiter, and Saturn? Which aren't?

My comment says: ...answers to the Space SE question Can James Webb take pictures of our solar system? In what ways will they differ from/compliment those from Hubble? suggest that at some point JWST ...
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1 vote
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Maximum number of pixels across a synthesized beam in an ALMA image?

I have some ALMA data, from which I have created images using the TCLEAN task in CASA. I understand that with this type of data, it is necessary to have at least 2 pixels across the FWHM of the ...
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2 votes
1 answer
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How much do collimation and viewing conditions affect magnification and viewing?

Before I start this post, I'd first like to make clear that this account is an alternate of my SovereignInquiry account--at the moment, accessing this account is much more convenient, so if things I ...
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2 votes
1 answer
46 views

What is the relation between size (radius) of an astronomical object and the speed of oscillation of 'light' coming from it? (Strength/amplitude)?

From the year-end issue of New Scientist Magazine (Dec. 18-31,2021): Astronomy: 'Space Cow' explosion was probably a failed supernova' Page 10: 'They found that the strength of this radiation ...
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4 votes
1 answer
296 views

Rising and setting time of planets in relation to the sun

If Venus set about 2 hours after the Sun,then it should be about 30degrees to the east of Sun. Is there any mathematical formula to get these thing or it's just a pattern? Source :https://olympiads....
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6 votes
2 answers
207 views

Identifying Constellations from Sky Maps

In Such sky maps How to identify constellation in those blocks?The just seems to me like Random figures. Please suggest some good sources where I can study this?
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2 votes
2 answers
148 views

Horizontal and equatorial coordinate systems

What is the difference between horizontal and equatorial coordinate systems apart from the notations (azimuth, altitude) and (right ascension and declination angle)? Please provide some measurements ...
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2 votes
1 answer
168 views

Calculating distance to High Redshift Galaxies based on observations

I am aware that we need to account for the expansion of the universe, changing $H$, the relativistic redshift eqn: $1+z=\sqrt{\frac{c+v}{c-v}}$ and so on, but can we accurately calculate velocity ...
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  • 405
5 votes
1 answer
660 views

How long would it take to realize there are "star-like objects" (i.e. planets) that change position in respect to the "fixed stars"?

If you were using unaided observations and were unfamiliar with astronomy (and maybe just pen and paper for recording anything), how long should it take to notice that Mercury, Venus, Mars, Jupiter ...
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1 vote
1 answer
55 views

Can I use an achromatic focal reducer to reduce chromatic aberration?

I am using 75/1000 Plano convex lens to build telescope. Can I use an achromatic focal reducer to reduce chromatic aberration?
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1 vote
1 answer
95 views

Can I use 75mm Plano convex lens to build telescope [closed]

I want to see Jupiter with moon. So am planning to build telescope. Can I use 75mm Plano convex lens with 1000mm focal length?
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2 votes
1 answer
72 views

Is our Milky Way galaxy (and its neighbors?) moving through the universe at 370 km/s (~828,000 mph) or 370 miles/sec (~1,332,000 mph)? [duplicate]

I swear that exactly half of the many, many sites I found say that our Galaxy and its immediate neighbors are moving towards the Leo Constellation (I believe) and, ultimately, supposedly, the 'Great ...
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2 votes
1 answer
121 views

Sun Moon earth Angle

I want to do a theoretical prediction before trying out an experiment. I just noticed that the arc separating the illuminated side of moon and the shadowed side is an ellipse arc. So Is it possible to ...
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1 vote
1 answer
50 views

How many asteroids were discovered via GAIA? Is there a list?

The ESA Science & Technology video Gaia's asteroid discoveries shows trajectories for hundreds of asteroids that were seen by GAIA, but as far as I can deduce from the extensive notes there, only ...
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1 vote
1 answer
79 views

Angle of Declination and Culminations

Is it true that angle subtended by the Zenith Distance at Upper and Lower culminations is equal to the declination of the star ?If It's true then why? Is the motion of Earth make the solid angle of ...
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0 votes
1 answer
56 views

Did astronomers ever use photographic plate rotation along with alt-az mounts?

The video Earth's Rotation Visualized in a Timelapse of the Milky Way Galaxy - 4K (linked below) and discussion below this answer to Why does a timelapse video of a stationary Milky Way make the ...
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2 votes
0 answers
72 views

What are the technological advancements that made it possible for modern large telescopes to work with alt-az mounts instead of equatorial mounts?

The video Earth's Rotation Visualized in a Timelapse of the Milky Way Galaxy - 4K (linked below) and discussion below this answer to Why does a timelapse video of a stationary Milky Way make the ...
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8 votes
1 answer
1k views

Why was the Cosmic Microwave Background (CMB) released at a blackbody temperature of 3000K rather than 30,000K?

If the ionization (or reionization, or Recombination) energy of atomic hydrogen is 13.6 EV, which corresponds to a black body temperature of 30,000K, why did the CMB not begin to appear then? Why did ...
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0 votes
1 answer
60 views

What is going on with comet C/2021 A1 Leonard? Is it going to be bright this weekend or not?

I have to plan an excursion to try to find clear evening skies to try to see if we can spot comet C/2021 A1 Leonard about 10 to 15° above the ocean in the Southwest after sunset this weekend. I'm ...
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-2 votes
1 answer
83 views

how would you explain the motions in the solar system? [closed]

like so i don't get it it does not make sense I'm confused
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1 vote
0 answers
71 views

Do observational astronomers make use of the Fredholm equation? Perhaps in solving for/removing instrumental effects in imaging?

The Fredholm equation of the first kind (Wolfram Mathworld and Wikipedia) written as (Wolfram's): $$f(x) = \int_a^b K(x, t) \ \phi(t) \ dt$$ where $K(x, t)$ is the kernel and $\phi(t)$ is an unknown ...
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0 votes
1 answer
78 views

Radar technique for distant objects

If we want to detect the distance to an object using radar, we can do it only for objects inside the solar system, otherwise the returning signal would be too weak to detect. On the other hand, we are ...
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0 votes
0 answers
20 views

3D/2D Universe Model (DSO, stars etc.)

I am looking forward to knowing some software/sites that show an extensive collection of the DSOs. I want it to be 3D, but it can also be 2D. I know/tried some of these, Stellarium - 2D Celestia - 3D ...
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10 votes
4 answers
3k views

Why do satellites appear as streaks in telescope images?

Can you explain me in simple words why the satellite in this telescope image appears as a streak? The exposure time is 1 second.
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1 vote
0 answers
99 views

What observational data was there that comet Leonard C/2021 A1 might have been dimming and/or breaking up?

Space.com's Comet Leonard, the brightest of the year, is fading and acting strange seems to be full of inexact language, like "something's wrong" and "unhealthy" and "goner&...
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2 votes
2 answers
46 views

How can photoionization release photons? As in the coronal emission of a nova star?

The photoionization process absorbs energy (light), it doesn't release it.... So how can some astrophysicists say that photoionization releases the light responsible for the coronal emission of a star ...
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2 votes
0 answers
67 views

What new fundamental knowledge could a very, very large optical telescope bring? [closed]

Very large baseline radio telescopes bring many mysteries of the cosmos to us. We build them because they are feasible. Say, in the future, we could build very large optical telescopes in deep space, ...
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2 votes
1 answer
82 views

Does the .43 arc-second per year deviation of Mercury's orbit from Newtonian predictions mean that its position is 'off' by 75 miles per year?

If I divide the elliptical circumference of Mercury's orbit by .43 arcseconds, I get an answer of almost exactly 75 miles.... BUT, it is the precession of the periapses that is off, not 'just' its ...
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3 votes
1 answer
77 views

What is the fraction of the time that the JWST could view a short transient event on-demand as a function of position on the celestial sphere?

In this answer to Why does JWST have such a big Blind Spot? I argue that this space telescope primary relationship with time is that it strives to look way back in it and so as long as a given ...
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0 votes
0 answers
15 views

Power Spectral Response Method

Can any one suggest me how we can apply the power spectral response method to calculate the best fit spectral index in python ? And plot the probability vs spectral index ?? Or any reference to ...
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1 vote
1 answer
260 views

Is a black hole found in the centre of the low-surface-brightness and dark-matter-free galaxy AGC 114905

Per information found on Internet: AGC 114905 was discovered while observing the constellation Pisces with the VLA ground-based radio telescope. The galaxy is about 250 million light-years distant ...
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2 votes
0 answers
32 views

What is the differential emission measure (DEM)? what are its physical significant in solar plasma? [closed]

I'm trying to understand what differential emission measure (DEM) is, especially its physical significant in solar plasma. Is it possible to give a short description and perhaps suggest to me some ...
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6 votes
3 answers
3k views

Could someone explain what is wrong with my telescope, and what should I be able to see with it?

In January of 2016, I received my first telescope, through Astronomers Without Borders. It was and is my first telescope: an AWB 130 Newtonian tabletop telescope with a 650mm focal length and a 130mm ...
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0 votes
1 answer
124 views

If the ratio of actual total mass to critical mass (Ω) in the universe is only about 0.3, why do cosmologists believe it is flat, as far as we see?

What about astronomical observations makes scientists believe our universe is flat, at least as far as they can tell? Despite the critical Friedmann density being less than one, plus the existence of ...
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3 votes
1 answer
268 views

How old is the idea of the far side of the Moon?

The far side of the Moon is the side which always faces away from the Earth, due to tidal locking. Due to libration, about 18% of this far side can be seen at one point or another through telescopes. ...
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21 votes
4 answers
4k views

Where is it possible to observe the Moon for 24 hours?

I wrote an astronomy olympiad yesterday and there was one task I couldn't figure out an answer to: Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. Under what ...
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1 vote
0 answers
46 views

Find Periodicity in Lightcurve Using Lombscargle Periodogram(Astropy)

How to find the Nyquist factor for unevenly sampled data like here.https://github.com/jakevdp/PracticalLombScargle/blob/master/figures/LINEAR_Example.ipynb ? I have time binned for 5 mins. I mean for ...
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5 votes
1 answer
700 views

Why are type 1b and type 1c supernovae called type 1 rather than type 2; if they result from large exploding stars, rather than accreting dwarfs?

What similarities do types Ib and Ic supernovae have in common with type 1a? Are their spectra or their magnitudes more similar to accreting white dwarfs than the other supermassive, main sequence, ...
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4 votes
1 answer
73 views

Can we measure planetary Love number of exoplanets?

I understand that Love number is the ratio between the tide raising potential to the actual deformation of the body, however, I'm not sure if there are ways to detect the Love number from observations ...
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15 votes
2 answers
2k views

Are there any gaps in the range of gravitational wave frequencies we can detect?

We have LIGO and other earth-based interferometers for detecting high-frequency gravitational waves, we're going to have satellites in orbit around the sun for low-frequency waves, and we have a ...
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  • 1,628
6 votes
1 answer
265 views

Can stars really be seen after sunrise from Mount Everest?

I came across this image taken on the "Balcony" at over 27,000 ft (8,200 m) elevation, beneath the summit of Mount Everest. So many stars can be seen on it even though the Sun has risen. Do ...
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1 vote
0 answers
59 views

Could we optically observe metallic hydrogen in space?

As many calculations have been done on whether metallic hydrogen is metastable or not in low-pressure environment, It occurred to me that by the fact that we have not observed any metallic hydrogen so ...
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