35 votes
Accepted

Why do satellites appear as streaks in telescope images?

Satellites are moving. They are in orbit around the Earth. Satellites in low Earth orbit are moving at about 7000 m/s relative to the ground. You can work out the orbital speed by $$v=\sqrt{\frac{GM}{...
James K's user avatar
  • 121k
29 votes

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. This drawing should explain it: (Note: It could be the other way ...
Ilmari Karonen's user avatar
26 votes
Accepted

Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?

No, not with the current or any projected "next-generation" of telescopes. The problem isn't dust, it is distance. To put it in context, you can consider a scale model of the universe. ...
James K's user avatar
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26 votes
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Why don't we just unshift the IR photos from Webb?

The infrared data cannot be unshifted to produce visually pleasing images simply by linearly scaling observed wavelengths because JWST does not work like the human eye nor like the camera in your ...
doubleunary's user avatar
20 votes

Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?

There is a fundamental limit to resolution called the "diffraction limit" that depends on three things: The angular size of the feature you're trying to resolve, The wavelength of light you'...
hobbs's user avatar
  • 758
18 votes
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Which are stars and which are noise in this comet photo?

Is that right? Yes. Is the fuzzy one an extended object? That would certainly be my guess (probably a distant galaxy). What causes so many isolated pixels to be so much brighter ...
Peter Erwin's user avatar
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15 votes

Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?

The only real problem is lack of angular resolution at optical and near infrared wavelengths. Lack of photons is not an issue. Suppose there were something the size of Jupiter orbiting Alpha Cen A. At ...
ProfRob's user avatar
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10 votes
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What is the "lost light" in this unusual Hubble Deep Sky image?

Let me see if I can explain the main aim and accomplishment of this work. First off: the picture you're puzzling over is a "luminance RGB" image, in which the bright regions are represented by color (...
Peter Erwin's user avatar
  • 16.7k
10 votes

Why don't we just unshift the IR photos from Webb?

You can't "unshift" images in the way you suggest because they often/usually do not contain objects that all have the same redshift. If they did, then you probably could, since all ...
ProfRob's user avatar
  • 152k
8 votes

What is the "lost light" in this unusual Hubble Deep Sky image?

When you plug the lead researcher's name into Arxiv, the first search result is The missing light of the Hubble Ultra Deep Field. 3 main steps: Creation of sky flat fields for the four filters....
Hobbes's user avatar
  • 3,034
8 votes
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What does "additive fringing from the (multiplicative) twilights" mean?

The fringing pattern is caused by thin-film interference within the CCD. The signal received in a pixel will be proportional to the light falling on it, multiplied by a sensitivity, but then some ...
ProfRob's user avatar
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8 votes
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Why does the background noise in this image of 2020 QG look like corduroy?

I agree that it’s noise in a fixed pattern, but I think it’s unlikely to be related to ADC sensitivity. Typically if you have multiple ADCs, they read out blocks of the sensor (e.g. one on each ...
Eric Jensen's user avatar
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8 votes
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If I can't unscramble an egg, how do Astronomers unscramble views gravitationally lensed by complex mass distributions?

I work in gravitational lensing, so maybe I can give you an idea. In those JWST you have a massive galaxy cluster that is bending the light behind and acting as a true lens. If you have a temptative ...
JOAQUÍN HERNÁNDEZ's user avatar
8 votes

Why don't we just unshift the IR photos from Webb?

I know this doesn't answer your question, but I thought I would mention it since it's mildly relevant. Here is a far ultraviolet (139.4 nm) image of the Sun that has been shifted into the human ...
Roy Smart's user avatar
  • 1,437
7 votes

Why do satellites appear as streaks in telescope images?

A relatively simply way to remove the streak is to take two-or-more photos, with a short pause between them. The stars won't move much in that time, but the satellite will have drawn a short dash on ...
Criggie's user avatar
  • 183
7 votes

Will the first Event Horizon Telescope image of the Milky Way's black hole Sgr A* just be another lumpy orange donut?

Yes. See today's press release from the Event Horizon Telescope. The image is remarkably similar to M87, but note that this a time-averaged composite over about 10 hours, because the emission from the ...
ProfRob's user avatar
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7 votes
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Why are photos from telescope stretched at their edges?

It's a general property of optics. In what way an image is distorted depends on the exact optical setup and will need careful calibration. Usually the best imaging quality is found in the center of an ...
planetmaker's user avatar
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7 votes
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Where can i find dark frames in the ESO archive?

Calibration frames, including dark frames, for the ESO telescopes in general and the FORS2 instrument in this case, are taken by a general calibration program rather than the specific science program. ...
astrosnapper's user avatar
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6 votes
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What is the size of the image sensor in the largest optical telescopes?

The current largest digital CCD camera is that of the Vera C. Rubin Observatory1 which has a whopping 3.2 gigapixels. The previous largest features on the Panoramic Survey Telescope & Rapid ...
Joseph Farah's user avatar
6 votes

Why does the background noise in this image of 2020 QG look like corduroy?

That looks like a fixed-pattern noise to me. Fixed pattern noise is a common sensor artefact for CCD sensors, One source for this is where you have less analog - digital converters (ADC) than pixels. ...
planetmaker's user avatar
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6 votes
Accepted

What simulator would I use to create an image of what our solar system looks like from Alpha Centauri?

The Sun has an absolute visual magnitude of about 4.75. Alpha Cen is 1.33 pc away. Thus the apparent magnitude of the Sun when viewed from Alpha Cen is 0.37. The Sun would appear as a point of light, ...
ProfRob's user avatar
  • 152k
5 votes

rms noise, confusion and dynamic range in radio images

RMS noise: Your understanding is mostly correct. RMS noise is the root mean square of fluctuations. Its square equals the sum of square of mean fluctuation and square of standard deviation of ...
terribleGuitarPlayer's user avatar
5 votes

Is it possible to use Photolithography for telescope image sensor?

The pixel size is not a major constraint on the imaging capabilities of an astronomical telescope. The angular resolution of the image is limited by diffraction at the aperture of the telescope. For a ...
Steve Linton's user avatar
  • 10.3k
5 votes

What does "additive fringing from the (multiplicative) twilights" mean?

The visual appearance of fringing is caused by the CCD (thickness) being comparable to the size of the wavelength (thin-film interference). An everyday example (same physics except with more colors) ...
Astroturf's user avatar
  • 1,111
4 votes

Why don't we see the gas behind the black hole?

The reason is that your animated gif shows a geometrically thin, optically thick accretion disk, whereas the disk around the M87 black hole is a geometrically thick, but optically thin disk. The main ...
ProfRob's user avatar
  • 152k
4 votes
Accepted

Streaks on a stacked star field

Those are probably just "hot pixels" that don't move on the sensor like the real stars do, so that the stacking spread them out in an arc. I don't think the software processes and treats ...
uhoh's user avatar
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4 votes
Accepted

Is it possible to use Photolithography for telescope image sensor?

Is it possible to use Photolithography for telescope image sensor? Sure, in the sense that CCDs and similar devices are already made using photolithography, and have been for decades. But since you ...
Peter Erwin's user avatar
  • 16.7k
4 votes

Converting an RGB image to fits (astropy)

I haven't done much astronomical image processing before, but as this question is unanswered I'll give it a shot - hopefully to some avail. If the problem is more specific, a code sample/image sample ...
Nitesh Menon's user avatar
4 votes
Accepted

Why do the Andromeda Galaxy images from NASA have some sort of color shifting in it

I think they are probably processing artefacts, because there are other artefacts there, and because the lines are parallel. I sent it through RGB saturation and found other artefacts of linear star ...
bandybabboon's user avatar
  • 4,252
4 votes

Why are diffraction spikes left in JWST public images?

Simple answer: false-color does not in any way "photoshop" the original image information. The term "cleanup" doesn't mean anything. Quite probably multiple images were ...
Carl Witthoft's user avatar

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