Questions tagged [image-processing]
The image-processing tag has no usage guidance.
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Where can i find dark frames in the ESO archive?
I am doing an image reduction with data from ESO but I can't find dark frames when I download the zip-folder even though I downloaded the associated callibration files. The image reduction I am doing ...
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How was this image of the faculae in the Occator crater obtained?
The picture in question (that I'm asking about) is at the bottom, of this post. Now, did they simply take a picture with reduced light intake? If so how much? 1/2, 1/4 or 1/8 or less? Or did they ...
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How can I better align stamps from Hubble images?
I am trying to do difference imaging with Hubble ACS/WFC images and have been using TweakReg to align images and cutout stamps. The problem is that residuals haven't been great and I'm looking for ...
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Understanding PSF models and PFSEx output
I understand that PSFs are models for spreading of light. When I visit Hubble website (https://www.stsci.edu/hst/instrumentation/wfc3/data-analysis/psf) there is PSF model for me to download. I could ...
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How do you estimate standard deviation of sky from (Hubble) image
I'm working on a simulation project with Hubble data and I need the standard deviation of the sky in ADU per pixel. Sometimes I can obtain a fits file (e.g. hdfs image), open this with astropy, and ...
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Finding Position angle and ellipticity to Deproject galaxy image using IRAF
I am trying to obtain position angle and ellipticity for a galaxy image by fitting elliptic isophotes using IRAF routine stsdas.isophote.ellipse package. After fitting the isophotes, I have a table ...
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How can someone take narrowband data from an OSC narrowband filter
To those who aren’t aware, an OSC narrowband filter is a filter with multiple band passes, for different emission lines. These can include a combination of Hα, Hβ, OIII, SII, and other emission lines. ...
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Where can I get raw photos of planets clicked by HST, Voyager 1 and 2, Cassini for Saturn and Galileo for Jupiter?
I intend to process RAW images of planets clicked by HST,Voyager 1 and 2, Cassini and Gallileo spacecrafts using a few softwares.
I am in search of where I can get these raw images from.
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Is there a standard deconvolution procedure to remove JWST's diffraction pattern yet? If so, would Arp 220 be a good candidate on which to try it?
Source: Webb captures the spectacular galactic merger Arp 220
Shining like a brilliant beacon amidst a sea of galaxies, Arp 220 lights up the night sky in this view from the NASA/ESA/CSA James Webb ...
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Credible description of point sources and point spread functions in astronomy
I am looking for a credible source (or even the original sources) that describe point sources and/or point spread functions (PSFs) on astronomy.
Unfortunately, the Wikipedia pages (point source, PSF) ...
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Effective gain when stacking N frame images
I am trying to understand how to derive the effective gain in [electrons / ADU] when stacking N frame images in different (summed, averaged, or medianed) ways. I found the effective gains for the ...
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Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?
NASA’s James Webb Space Telescope has taken very blurry "photos" of exoplanets around distant stars, such as the exoplanet HIP 65426 b, in different bands of infrared light:
My question is, ...
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How to reproject a fits file using MontagePy
I am fairly new to image reprojection so I am trying to use MontagePy to go from a bigger fits file to its smaller subsection (which is in a different observation, therefore header) but the output ...
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How to use SExtractor to calculate Petrosian Radius?
I'm using Sextractor to run some benchmarks on the code I'm working on.
I'm mainly focused on Petrosial Radius (PETRO_RADIUS).
I have two main questions that I could not find in the documentation:
...
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What do negative values on bright sources in TIRSPEC mean?
I opened a FITs image data from TIRSPEC (NIR imaging) (an HgCdTe infrared imaging sensor) on DS9 and I saw that some of the bright stars have black patches at the center (negative values).
Can you ...
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Can I use ENVI Classic to process JWST tiff image?
I am interested to process JWST or any other astronomical images. Can I use ENVI Classic to process it? I have some JWST tiff images and I would like to know about the gasses, compounds, the ...
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Are magnetic vortices capable of providing magnetic lensing when observed away from the poles
Magnetic vortices-(ESA cluster mission from observations November 2018)(article, ESA, science & exploration: 'Magnetic Vortices explain mysterious auroral beads'. An observer during Saturn's ...
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If I can't unscramble an egg, how do Astronomers unscramble views gravitationally lensed by complex mass distributions?
Quanta Magazine's Two Weeks In, the Webb Space Telescope Is Reshaping Astronomy highlights two submissions to arXiv soon after the first images were released: "Three days later, just minutes ...
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SNR computation + noise correlation [closed]
My question splits in two parts:
If I have an image with N x N pixels, and an object in the center (star, galaxy what have you), spanning M x M, how do I compute its signal to noise ratio exactly?
...
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Why are diffraction spikes left in JWST public images?
First released JWST images are amazing. However, given the amount of image processing, false colours, cleanup etc. that must have gone into these images, why not also remove or reduce the diffraction ...
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"Quarter root of intensity" in coronographic plots
In excitement regarding the JWST release, I came across Krist et al, The JWST/NIRCam coronagraph: mask design and fabrication, within which there is the following plot:
Fig. 9. Focal plane images ...
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Why do the Andromeda Galaxy images from NASA have some sort of color shifting in it
I was checking the images from this website of the Andromeda Galaxy.
However, I noticed that low res images look good, however, the 1.7Gb images has some sort of color shifting in it:
Is there any ...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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 ...