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Questions tagged [observational-astronomy]

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

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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
43 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 ...
2
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1answer
40 views

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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91 views

A gedanken on being able to navigate back to Earth [migrated]

Imagine a sphere centered at Earth with a radius of 4 light years. Suppose we pick a random point on the surface of this sphere and drop someone, let us say, "Joe" there. Will Joe be able to come back ...
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1answer
58 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
65 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
58 views

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
74 views

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
36 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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0answers
32 views

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 ...
2
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2answers
83 views

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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3answers
220 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
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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
45 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
45 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
85 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
82 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
131 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
53 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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143 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
49 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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0answers
47 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
54 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
363 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
33 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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86 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
61 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
52 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 ...
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2answers
226 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 ...
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0answers
42 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
295 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 ...
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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 ...
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1answer
196 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 ...
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1answer
82 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 ...
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1answer
82 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
125 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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247 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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64 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
101 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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88 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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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,...
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1answer
165 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?
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1answer
150 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
52 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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31 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 ...
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1answer
41 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 ...
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3answers
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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 ...
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1answer
98 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 ...
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1answer
92 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 ...
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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 ...