Questions tagged [image-processing]

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Why are photos from telescope stretched at their edges?

You may know the issue that photos from (at least some) telescopes are stretched at the edges, so that the star locations do not fit compared to if this location would be on the center of the photo. ...
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1 vote
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How to get high-quality sky image for specific location & date

I'm working on an ink drawing album cover inspired by this Frank Hurley photo from the First World War, and want to put an accurate starry sky behind it in my album artwork.: The tower in the image ...
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Do I need ENVI if I want to just learn IDL?

I am trying to gain experience in IDL in order to do basic image data reduction techniques like stacking and aperture photometry, so I decided to purchase an IDL license, however, the license is ...
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2 votes
0 answers
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align an image to celestial North

I'm producing images from FITS files, But most of my images aren't aligned to the celestial north. I would expect there to be a simple library, or even an astropy command to make the alignment of the ...
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6 votes
0 answers
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Using tail-fit Gaussian distribution to compensate for saturated sensors

Main Question I have a project goal, where I have an image of light sources (stars or lamps doesn't matter). The image is split up into channels for each expected band of 'color'. There are occasional ...
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2 votes
0 answers
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How to subtract background correctly?

I want to perform sky background estimation and subtraction. To do that, I am adopting some libraries in python, i.e. photutils which does have *some support for background estimation. However, I ...
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3 votes
1 answer
155 views

What are some astrophotography editing options and strategies for taking photos of galaxies with a telescope and a cell phone?

We purchased a phone adapter for my sons telescope and got some amazing pictures, BUT we believe that they can be clearer. What is the best, or a really good, image editing program for amateur ...
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3 votes
1 answer
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Hoping to do some viewing and astrophotography with a large-ish Dobsonian and a DLSR, is this scheme workable?

I haven't put a camera behind a telescope since the lunar eclipse of 1975 except for a few experiments with a cell phone held behind a pair of binoculars. I want the occasional thrill of using a ...
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1 vote
0 answers
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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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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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5 votes
0 answers
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rms noise, confusion and dynamic range in radio images

I have been trying to understand imaging in radio astronomy. Below are some of my questions related to it and my understanding of their answers. I am not very confident about my understanding of them ...
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5 votes
1 answer
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Are there automatic methods to locate (stellar and supermassive) black holes?

Black holes have been discovered using several techniques, as outlined by How are black holes found?. What I was wondering is: are there automatic methods for locating them (e.g., artificial ...
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2 votes
0 answers
36 views

Frame used for RGB cube in SAOImage

I have RGB FITS images with NAXIS=3 so I read them into SAOImage (ds9 8.2.1). I use this command line: $ ds9 -rgbcube myimage.fits Doing so, the window is split in ...
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6 votes
1 answer
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Why are the radio images of the jet of 3C 273 different?

At NASA/IPAC Extragalactic database, we can see images of the jet of matter being ejected from the quasar 3C 273. Here are a couple from the radio spectrum as examples: My question is: why are the ...
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4 votes
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Why do the Centaurus A radio jets have two "arms" each? (Event Horizon Telescope image)

Fig. 2: Image analysis of the final model: a, Model image corresponding to the image from Fig. 1 with a pixel size of 2 μas. Here, the tentative position of the jet apex is indicated with a circle. ...
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2 votes
0 answers
41 views

healpix: creating isometric tiles for flat map of survey

I am currently tasked with creating a visual of a recently completed survey which is in HEALPix1 format. I am also required to use the DSS and Planck skymaps also in HEALPix, and would like to flatten ...
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2 votes
1 answer
73 views

What was the first use of time-delay integration in Astronomy? Are there instances before GAIA?

In the context of GAIA, time-delay integration is the clocking of a CCD's charge shift register at a frequency such that it matches the linear speed across the focal plane of the actual image. So even ...
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2 votes
1 answer
170 views

Streaks on a stacked star field

Stacking by Sequator 100 dng photos of night sky taken with a smartphone resulted in a (beautiful, I would say) populated star field where undesired arc streaks are seen all over the field. It is like ...
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2 votes
0 answers
59 views

How to use DeepSkyStacker to increase detail, reduces noise, and not lose colour?

I had my first attempt at shooting the Orion Nebula and am pleased that I saw it for the first time. Very exciting. I shot 10 frames and then stacked them using DeepSkyStacker which brought out all ...
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1 vote
0 answers
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What produces all of these small radial striations in this very overexposed image of a star by Hubble's WFC2? (the four big ones are from the vanes)

In a recent astrometry question in Space SE I needed to check Proxima Centauri's position and the article contained the image below. I've saturated the colors, cropped it, and added a "...
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3 votes
0 answers
278 views

Issues in dimensions and slicing while plotting contours over a FITS Image in Astronomical Plotting Library in python (APLpy)

I have been trying to plot the contours of a FITS image over itself in APLpy. The image was created in AIPS, and has dimensions (1024,1024,1,1), viz., right ascension (RA--SIN), declination (DEC--SIN),...
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7 votes
2 answers
145 views

Is it possible to use Photolithography for telescope image sensor?

The current largest digital CCD camera is the Vera C. Rubin Observatory, which has a whopping 3.2 gigapixels with a pixel size of 10 micrometers. In contrast, Agfa 10E56 holographic film has a ...
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7 votes
1 answer
137 views

What is the size of the image sensor in the largest optical telescopes?

What image sensors (imaging electronics) are used in telescopes? Like CCD, is that the best option? What is the typical physical size and resolution of the photo-sensitive surface of the currently ...
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2 votes
1 answer
64 views

Computationally intensive technique to search for TNO's within the noise of historical photographic data?

I remember reading recently about a technique to search through lots of old survey images to try to identify trans-Neptunian objects that were so dim that they were "lost in the noise" in ...
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2 votes
1 answer
111 views

Where can I find thousands of actual images of stars in the galaxy?

I'm trying to write a program to differentiate between images of stars and nebulae. However, I'm not able to find a large enough dataset of actual images of stars that I can use to train my deep ...
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0 votes
0 answers
26 views

Limit Magnitude divide 2 arcsec

How can I derive limit magnitude in 5sigma/2arcsec ? I have the limit magnitude in 5sigma which derive from the magnitude with SNR reach 5. But I can not understand what the meaning of dividing ...
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4 votes
1 answer
274 views

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

@HDE226868's answer to Why doesn't the black hole in the center of the Milky Way glow similarly to the famous M87 image? explains that neither black hole is orange and any Event Horizon Telescope ...
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1 vote
0 answers
51 views

How can I create a mask for a fits image?

I need to create a mask of a fits image. By this I mean that I want to create the image that covers all secondary objects from the original image except the one is in the center. I have some routines ...
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5 votes
0 answers
137 views

Point spread function image deconvolution

I would like to deconvolve an image of Saturn. I took an image of Saturn: Stack of 50 frames, the angular resolution of the original frames is 1.6''/pixel and the frames are scaled x4 before stacking....
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5 votes
2 answers
687 views

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

The news item Small asteroid becomes closest ever seen passing Earth: NASA contains a "handout image" with the caption: This NASA/JPL/ZTF/Caltech Optical Observatories handout image ...
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3 votes
1 answer
569 views

Searching dataset for Constellation detection

I need to develop an Machine Learning (ML) model for predicting constellation seen in a picture taken from a mobile. This I need to develop from scratch. Firstly, I need help finding a database which ...
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7 votes
2 answers
391 views

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

The question How can I make the fringing pattern visible in my flat (twilight) images for filter i? includes: I have a bunch of twilight flats that have been preprocessed (dark, bias, overscan etc.)...
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2 votes
2 answers
85 views

How can I make the fringing pattern visible in my flat (twilight) images for filter i?

I have a bunch of twilight flats that have been preprocessed (dark, bias, overscan etc.) and need to remove the additive fringing from the (multiplicative) twilights. I normalized each one by dividing ...
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2 votes
0 answers
126 views

How are small objects automatically identified and their locations determined in digital images?

I have a large quantity of old digital images of low energy electron diffraction (LEED) patterns that I must process to identify and locate small, sometimes elongated gaussian-like blobs of a few ...
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0 votes
0 answers
27 views

How to use the APARM, BPARM and CPARM of REGRD task in AIPS?

I plan to regrid a 500 by 500 image in B1950 to 500 by 500 in J2000 using the AIPS task REGRD. How to proceed?
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17 votes
4 answers
3k views

Which are stars and which are noise in this comet photo?

The Forbes news article NASA's Hubble Telescope Snaps Best Images Yet Of Our First Interstellar Comet shows the image below (which I have since annotated) of comet 2I/Borisov (C/2019 Q4) and links to ...
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1 vote
1 answer
687 views

Converting an RGB image to fits (astropy)

I am trying to save a NumPy RGB array (a 3d array with dimension 512x512x3), to a .fits file using astropy.io. Saving this array to a .png file works fine, but when ...
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1 vote
1 answer
133 views

False-color wavelength assignments in this "drop-dead gorgeous" image of NGC 2903?

C|Net's Hubble spots drop-dead gorgeous spiral galaxy tucked into Leo links to NASA's Hubble Spots Stunning Spiral Galaxy which shows the image below. The caption on the NASA page doesn't mention the ...
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1 vote
1 answer
235 views

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

In computer simulations of what a black hole might look like and many artist renderings of black holes, they all seem to show the brightly glowing gas BEHIND the black hole due to gravitational ...
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16 votes
3 answers
1k views

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

The Daily Galaxy article “The Lost Hubble” –New! Deepest Image of the Universe Ever Taken says: To produce the image a group of researchers from the Instituto de Astrofísica de Canarias (IAC) led ...
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2 votes
0 answers
67 views

Issue translating World Coordinate system to cartesian coordinate

I have two fits images from the WFC3 that I am trying to combine with a C# program. When I try to combine multiple images I don't think the values I am getting for my x/y coordinates (calculated from ...
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8 votes
4 answers
309 views

Image sets for testing stacking algorithms?

I am looking for sets of astronomical images for testing different kinds of stacking algorithms. The idea is simple: if one has $N$ images of the same object, the signal-to-noise ratio of the ...
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