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Questions tagged [observational-astronomy]

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

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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 ...
4
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3answers
123 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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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
24 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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1answer
43 views

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
76 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 ...
2
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1answer
75 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.
4
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1answer
124 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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2answers
51 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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3answers
70 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
46 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'...
2
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0answers
45 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 ...
2
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1answer
53 views

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
362 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 ...
3
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1answer
32 views

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 ...
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0answers
82 views

Which astronomer set his beard on fire because he left the cap off his telescopes finder?

There is a famous story of an experienced astronomer setting his beard on fire because he left the cap off his telescopes finder. I know it's said to be true of Galileo, but I thing it's relatively ...
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0answers
58 views

Is there any formulae to calculate whether the sun will depress 18 degrees or more below the horizon on a certain day / location?

I'm trying to code a piece of software which will calculate some times for me that would greatly help me in my day to day but none of my formulae work if the sun doesn't go at least 18 degrees below ...
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1answer
43 views

The Solar Motion and the peculiar velocities of stars

Local standard Of Rest is the hypothetical origin of a reference system with respect to which the motions of all stars in some neighborhood of the sun average out to be zero which type of motions of ...
8
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2answers
216 views

Why moon sighted only in Kerala but not in rest of India?

I know for most of you the question may look silly, but Kerala is a state in India where the moon (Ramadan moon) will be sighted but not in rest of India. I was reading the news article where I got a ...
2
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0answers
38 views

What's the profound reason(s) why the star formation rate drives the scatter of the mass-metallicity relation in galaxies?

Since decades it's well known that a correlation between stellar mass and metallicity (Z; both stellar and gas-phase Z, but here I focus on the gas-phase Z) exists (e.g., Tremonti+04; analysis of >...
2
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4answers
220 views

Is it practical to build a giant telescope in Moon? (Considering the fact that the atmosphere of moon is very rare)

China's FAST (Five-hundred-meter Aperture Spherical radio Telescope) is the largest radio telescope in the world.(This is huge!!!) As we all know Space Telescopes are better than Earth-Based ...
2
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0answers
50 views

How to become an astonomer? [duplicate]

I am very much interested in becoming an astronomer as a career. I know that my main focus should be in mathematics and science but; are there any specific degrees or competitive examinations I must ...
6
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1answer
185 views

How much do starlight and artificial light illuminate the Moon?

The Moon receives most of its light from the Sun, either directly through sunlight or indirectly through Earthshine. However, there are many other dimmer sources of illumination. Starlight. This is ...
4
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1answer
81 views

Is it possible to image a meteor so the rock is visible?

I was wondering what one would see if they were to look through a telescope tracking a meteor as it shot through the sky. Technology aside, would one be able to see the object tumbling or would it ...
0
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1answer
61 views

Redshifting restframe SED

I have a template spectral energy distribution (SED) at z=0. I want to shift the template SED to an arbitrary redshift (z>0), how to do this in python?
4
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1answer
104 views

Implementation of formulae for Meeus for the Moon

With Astronomical Algorithms by J. Meeus (1998) I have obtained the relevant illuminated fraction of the disk and position angle. But they're numbers (all Greek to me!) I know, Meeus explains that ...
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0answers
167 views

What are the “lines” in a constellation or asterism called?

Is there a technical term for the "lines" in a constellation or asterism? Alternatively, is there an astronomy related coloquialism or any informal term that refers specifically to these lines, and ...
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0answers
55 views

What is the canonical method to calculate the surface brightness limit of a 2D image, e.g., in a 1 arcsec2 aperture?

What is the canonical method to calculate the surface brightness limit of a 2D image, e.g., in a 1 arcsec2 aperture? ...if image has erg/s/cm2 units and each pixel has some arcsec2 dimension.
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2answers
100 views

planets are point like

Need Help. I have a problem with my 50 mm objective with 500mm focal length refractor telescope. I can see moon clearly. I have 18 mm and 9 mm eyepieces. I see Jupiter and Venus as a bright point ...
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0answers
84 views

How to trim CCD overscan and amplifier turn on/off regions

I have begun reducing images I collected with a telescope and CCD detector. I read in the the "Handbook of CCD Astronomy" by Howell that I need to trim overscan regions (as well as possible amplifier ...
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0answers
79 views

How do I calculate the hour angle of a planet's moon from a point on that planet's surface?

I'm worldbuilding and I'm trying to construct a standing stone calendar that'll accurately denote where to look for my planet's moon at its four major phases from 53.8 degrees South. So, I need the h0,...
5
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1answer
145 views

How is it ensured that a parabolic shape forms while polishing a telescope mirror?

I understand polishing the mirror with a successively finer abrasive can create a curvature, but how is it possible to obtain a uniform curve that forms a parabola while polishing by hand?
3
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1answer
146 views

Might the SpaceX Roadster intercept any ongoing surveys?

There are star survey telescopes in space, and on Earth. I don't really know how to begin to know where they will all be looking for the next few months. On the off-chance that someone does, or can ...
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1answer
47 views

Parallax and luminosity question about Arcturus, compared to terrestrial light? [closed]

From the rooftop, certain lights look roughly as bright as Arcturus. If these lights emit a power of 10 W and are 5 km away. What does that tell you about Arcturus? If you assume all stars are ...
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0answers
30 views

Estimating Earth's Rotation with Two Star's Measurements?

Look for a bright star and measure its position (altitude and azimuth) in degrees. Repeat the measurement after some time and use these values to estimate the Earth’s rotation speed ...
3
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1answer
40 views

Comparing Light Collection Between Pupil and Telescope?

The amount of light collected for a period of time is proportional to the area of the collecting aperture. We use our eyes -pupils have diameters of approximately 5 mm-, binoculars and telescopes. How ...
8
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3answers
2k views

Is the James Webb telescope going to orbit around the earth?

If it’s going to orbit around the earth, what kind of orbit would it be (what distance)? Are there benefits to sending a telescope further away from the earth if it’s just to photograph galaxies and ...
4
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1answer
85 views

How do observational astronomers manage streaks and other artifacts from objects in Earth Orbit?

There are thousands of satellites and spent rocket parts in low earth orbit (LEO). Mostly near the lines of dawn and dusk they can be in sunlight while observatories below are still viewing the night ...
4
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1answer
84 views

How do we measure the mass of a star?

I recently came across the book intro to cosmology by j.v. Narlikar, where it mentions about quarks and other star and inadvertently uses mass of sun as reference. I want to know how me measure mass ...
2
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0answers
38 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 ...
2
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1answer
172 views

What should be the declination of a star to be marginally circumpolar given the latitude & height from ground?

If I'm given the latitude, I can easily find the declination by using declination = 90 - latitude. I can also find the angle of dip from the height but should I add or subtract it from the declination ...
3
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1answer
82 views

If I look beyond (about same region, higher redshift) a galaxy, will I see its progenitors?

Is there a range of redhsift dz, such that if I look at z+dz from a massive object at redshift z, I will see its progenitors? (in a LCDM scenario of halo assembling, with smaller halos evolving ...
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0answers
37 views

Finding individual band magnitudes: Why and how is the integration of individual flux values for each wavelength used?

What differentiates the distance modulus equation to find the difference between two apparent magnitudes? For example, $$ m_1 = -2.5\cdot log_{10}\left(\frac{F_1}{F_2}\right) + m_2$$ leads to the ...
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2answers
60 views

How small a location is possible to identify when any visible star is at its zenith directly above?

How small an area on Earth is it possible to identify with any precision when any celestial object (star, planet, comet, nova) (visible with the naked eye alone) is at its zenith directly overhead? --...
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0answers
38 views

How the observed deuterium abundance constrains big bang nucleosynthesis?

I know deuterium can be used as a good tracer to constrain the big bang nucleosynthesis. But can anyone tell me the in details how this is actually done?
4
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1answer
182 views

How to visually tell the difference between a planetary nebula and a supernova remnant?

If we see a nebula by looking through a powerful telescope, how can we tell whether we are looking at the remnant of a supernova or at a planetary nebula? Thanks
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2answers
160 views

Did Tycho Brahe improve measurements twentyfold?

I am reading a book on the Coopernican Revolution where the author states that Tycho Brahe was able to make twenty times more accurate measurements than any of his predecessors. On the other hand, I ...
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1answer
82 views

Metals and dust locked into planets

I wonder what is the contribution of metals and dust locked into planets, with respect to the amount in the interstellar medium (ISM). In other words, when we measure the metallicity and the dust mass ...
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0answers
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Which physical quantity is the real/definitive tracer of galaxy evolution? [closed]

Which physical quantity is the real / definitive tracer of galaxy evolution? Let me explain better: if you aimed at understanding as much as possible about the evolution of galaxies and you had to ...
5
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1answer
211 views

How (the heck) was this photo of Venus at inferior conjunction (between us and the Sun) taken?

This great answer by @gerrit discussing planetary phases seen in visible light contains the image I've included below. According to the Wikimedia Commons link these are ESO images from the Venus ...