Skip to main content

Questions tagged [image-processing]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1 vote
0 answers
68 views

Declinations from stars apparent motion w/o plate solving

I am trying to program the calculation of the declination of the stars, based on their apparent movement through a series of astrophotographs, purely algebraically, without using a solver based on the ...
Danko Dnevic's user avatar
1 vote
0 answers
35 views

Stacking of frames drizzled using the AURA drizzle implementation hosted on github/spacetelescope (NOT PixInsight drizzle integration)

Note: this question is not about PixInsight's drizzle integration module, it's specifically about the mentioned drizzle implementation. Answers describing PI functionality are automatically off topic. ...
Adrian K-B.'s user avatar
9 votes
6 answers
4k views

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

I’ve been going back and forth with peers on why image processing is done the way it is on the Webb Telescope. Based off some article, my understanding is that they have various filters that represent ...
lumenhippo's user avatar
5 votes
2 answers
241 views

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

The wikipedia article on Alpha Centauri has an image of that system from earth. I'm hoping to make the opposite image. I realize that there are various discussion of roughly what it would look like (e....
jackisquizzical's user avatar
4 votes
1 answer
235 views

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 ...
Mich Vaughan's user avatar
3 votes
1 answer
86 views

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 ...
Sven _Andersson's user avatar
0 votes
0 answers
40 views

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 ...
cassandra's user avatar
3 votes
3 answers
159 views

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 ...
cassandra's user avatar
1 vote
0 answers
84 views

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 ...
cassandra's user avatar
0 votes
0 answers
46 views

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 ...
B. S.'s user avatar
  • 11
2 votes
1 answer
265 views

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. ...
Topcode's user avatar
  • 166
4 votes
1 answer
181 views

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.
Dhruv Nayak's user avatar
8 votes
0 answers
221 views

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 ...
uhoh's user avatar
  • 30.7k
2 votes
0 answers
84 views

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) ...
mapf's user avatar
  • 121
1 vote
0 answers
69 views

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 ...
cosmozaka46's user avatar
16 votes
7 answers
5k views

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, ...
user3163495's user avatar
2 votes
1 answer
125 views

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: ...
Igor Kolesnikov's user avatar
1 vote
0 answers
66 views

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 ...
Rian's user avatar
  • 503
1 vote
0 answers
39 views

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 ...
Dan's user avatar
  • 11
4 votes
0 answers
52 views

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 ...
Butch's user avatar
  • 49
12 votes
1 answer
811 views

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 ...
uhoh's user avatar
  • 30.7k
3 votes
1 answer
125 views

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? ...
Jylu's user avatar
  • 61
2 votes
1 answer
630 views

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 ...
gandalf61's user avatar
  • 657
5 votes
0 answers
70 views

"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 ...
0xDBFB7's user avatar
  • 151
5 votes
2 answers
214 views

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 ...
user avatar
4 votes
2 answers
456 views

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. ...
user184868's user avatar
2 votes
0 answers
90 views

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 ...
S. Imp's user avatar
  • 395
2 votes
0 answers
88 views

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 ...
Robin's user avatar
  • 41
4 votes
1 answer
1k views

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 ...
Kipod23's user avatar
  • 41
7 votes
1 answer
127 views

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 ...
probinso's user avatar
  • 173
2 votes
0 answers
348 views

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 ...
x12red's user avatar
  • 31
3 votes
1 answer
193 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 ...
SSmith3's user avatar
  • 69
4 votes
1 answer
179 views

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 ...
uhoh's user avatar
  • 30.7k
1 vote
0 answers
77 views

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 ...
uhoh's user avatar
  • 30.7k
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.
Gargolla9's user avatar
  • 111
6 votes
1 answer
1k views

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 ...
user307105's user avatar
5 votes
1 answer
232 views

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 ...
nicolopinci's user avatar
2 votes
0 answers
110 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 ...
dom_beau's user avatar
  • 121
6 votes
1 answer
106 views

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 ...
Jim421616's user avatar
  • 2,538
4 votes
0 answers
91 views

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. ...
uhoh's user avatar
  • 30.7k
2 votes
0 answers
95 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 ...
triple7's user avatar
  • 153
2 votes
1 answer
123 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 ...
uhoh's user avatar
  • 30.7k
2 votes
1 answer
239 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 ...
Alchimista's user avatar
2 votes
0 answers
66 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 ...
Magic Bullet Dave's user avatar
2 votes
0 answers
132 views

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 "...
uhoh's user avatar
  • 30.7k
3 votes
0 answers
692 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),...
lordparthurnaax's user avatar
7 votes
2 answers
172 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 ...
Ilya Gazman's user avatar
7 votes
1 answer
220 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 ...
Ilya Gazman's user avatar
2 votes
1 answer
71 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 ...
uhoh's user avatar
  • 30.7k
2 votes
1 answer
216 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 ...
VS123's user avatar
  • 21