18

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 than the background? Is this just the tail of a statistical distribution of shot noise, or are there other mechanisms that can produce single pixel noise many ...


9

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 (a sort of pseudo-true color using near-infrared images), with the second faintest parts represented with black and the very faintest parts with white. The ...


8

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. This process is fully described in Sect. 2.4. – Creation of a catalogue of all WFC3/IR datasets that may affect our mosaics (including calibration ...


8

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 extra signal is added or subtracted which depends on how much of the incoming light is at particular wavelengths that are affected by the interference (i.e. the ...


8

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 corner to read out a quadrant). And sensitivity differences across those amplifiers usually is removed pretty well by flat-fielding. In my experience, you get things ...


6

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. Say, you have N ADC, each with its own sensitivity. Then you have in the resulting image a sensitivity pattern which repeats every N pixels. Depending on ...


6

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 Response System (Pan-STARRS), and has a resolution of ~1.4 gigapixels.[1] Based on the spec sheet provided by the Vera Rubin Observatory, the LSST camera has a ...


5

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) is an oilslick one sees in a puddle. The wavelengths of visible light are similar in size to the layer of oil on top of the water. The slight variation in ...


5

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 reasonable pixel size, the telescope geometry can then be designed so that each pixel corresponds to a region of sky smaller than that angular resolution, so ...


4

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 each star separately, they can't be "skipped stars" mingled with "recognized stars". Notice that they are all 1 pixel wide, whereas stars are ...


4

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 then go on to ask: Will it be possible to use a chemical image sensor to achieve a nanometer pixel size? it seems that your focus is on the idea that increasing ...


4

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 would probably be useful for further diagnosis, but otherwise this example may help. It discusses the process of writing a 3-channel image to separate FITS ...


3

This GIF is made (via giphy.com) from the new NAASA Goddard video Hubble's New Image of Interstellar Object. It shows the comet moving at quite a clip! This shouldn't be a surprise. From the link in the question https://archive.stsci.edu/proposal_search.php?mission=hst&id=16009 the coordinates for the first and last exposure are: RA ...


3

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 difference is that you do not see any evidence of the structure of the disk in the picture - it is nearly transparent. You do however see plenty of ...


3

This is usually referred to in astronomy as the "drift scan" technique, and has actually been used with ground-based telescopes since the early 1980s (e.g., McGraw, Angel, & Sargent 1980, Wright & Mackay 1981). Gibson & Hickson (1992) have a summary of work done in the 1980s and early 1990s in the Introduction section of their paper; ...


2

The quick answer is yes, we indeed see real changes in the structure of the jet. Longer answer; There are several factors that define how the jet of 3C 273 looks like: frequency of observation, telescope/array used, and real changes in structure. If we observe with interferometry technique from Earth, the higher the frequency - the better the resolution and ...


2

Dark Energy Survey data have yielded several TNO discoveries. Bernardinelli et al. 2020 describe their method in detail. First they compute a trial orbit from images where a transient object was detected. Then Final validation of the reality of linked orbits uses a new "sub-threshold confirmation" test, wherein we demand the object be detectable ...


2

The online version of the digitised sky survey will give you as many images of the sky as you want. Be aware that these are based on photographic plates. Also be aware that every imaging system has its own peculiarities in terms of the shape of the point spread function (i.e. the shape of a star in the image) and features such as diffraction spikes. https://...


1

If actual photographs are not required, Stellarium could render a suitable set of reference images. Use the Perspective (gnomonic) projection for the closest match to a photograph, and display only the features you want. Its scripting capability may help you avoid repeating some manual operations. Here are a sample pair of Stellarium images. The first has ...


1

Fringing is normally very difficult to see in twilight sky flats with broadband filters (the i filter is 100 nm wide). The fringing is caused by thin-film interference at particular wavelengths defined by spectral lines (OH lines in the i-band) in the the light from the sky. At twilight, the sky background is completely dominated by scattered sunlight, ...


1

Is that right? No. The streaks are fast-moving objects in the view of the telescope -- Other satellites. Hubble is in a fairly low orbit (it can be visited) and there are plenty of satellites around and above it, including in its field of view. (For obvious reasons, the streaks are not caused by aeroplanes, a usual contender for streaks). What gives it ...


1

Spacetelescope.org indicates under "Colours & filters" that the blue channel of the image is from a 658 nm filter (red) and the red channel is from an 814 nm filter (near infrared). The cyan and orange rows of the table also list these filters; presumably the green channel is a blend of the two. The ACS instrument handbook says filter F658N is narrow, ...


Only top voted, non community-wiki answers of a minimum length are eligible