Questions tagged [python]
Questions about using the Python programming language to solve astronomical problems. General questions about Python are off-topic but might be asked on Stack Overflow.
170
questions
21
votes
3
answers
5k
views
Why won't the Sun set for days at N66.2 which is below the arctic circle?
Correct me if I am wrong, but if we count sunsets by the center of the Sun apparently crossing the horizon then the Sun is supposed to set every day at latitudes under the arctic circle. (Yes if you ...
- 313
18
votes
2
answers
4k
views
Why does the Fourier transform of this CMB image have a hole in it?
The BBC's Desert telescope takes aim at ageing our Universe contains the image below of the Cosmic Microwave Background from the Atacama Cosmology Telescope or ACT. It looks like this is plotted with ...
- 31.4k
9
votes
4
answers
3k
views
Generate a uniform distribution on the sky
How to generate a uniform distribution of stars on the sky ? What I want is make a simulation of random points following uniform distribution on a part of the sky (making the assuption that we have ...
- 321
8
votes
3
answers
12k
views
How do I plot galactic coordinates using matplotlib and astropy in python?
I want to make a projection of millisecond pulsars on the galactic plane, much like this one from Sala et al. 2004:
I have tried several methods, and have not gotten anywhere. This is my current ...
- 185
7
votes
2
answers
460
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.)...
- 31.4k
7
votes
1
answer
5k
views
How can I convolve a template spectrum with a photometric filter response spectrum?
Suppose I have a template stellar population spectrum (say, from Bruzual & Charlot 2003) which runs from like 1000 Angstroms to 160,000 Angstroms and which has x-axis wavelength units of Angstroms ...
- 693
6
votes
3
answers
1k
views
Open source code for the maths behind a heliostat?
Theoretically, using a Raspberry Pi, (at least) one mirror, and two motors, one should be able to build a heliostat, i.e. a device which redirects sunlight to a fixed spot, like a scrub in the shadow ...
- 5,526
6
votes
2
answers
1k
views
Get orbital period of exoplanet from light curve using astropy.timeseries
I am using astropy and I would like to calculate orbital period of an exoplanet by its star's light curve. I follow tutorial in astropy docs and I use data from Kepler in Nasa Exoplanet Archive.
...
- 313
6
votes
1
answer
618
views
Cannot identify mistake in calculating orbital eccentricity vector; magnitude equals one instead of zero (with python code)
I have a gravitational nbody simulation, for which I would like to determine various orbital parameters. For each body, I have 3-D vectors (x,y,z -space) for position, velocity, and acceleration. I am ...
user33354
6
votes
0
answers
116
views
Kepler ellipse orbit fit issues
I am helping my high schooler with a research paper that uses PyAstronomy to fit the orbit of stars around Sag A. It isn't working because the angles (parameters Omega, omega, and i) seem to have a ...
- 61
5
votes
1
answer
754
views
Astropy units issue
hope you're all doing well.
I'm not very familiarized with AstroPy and I'm having a problem computing the conversion between angular momentum units.
If I define the ...
- 605
5
votes
2
answers
700
views
Comoving distance between two points [(RA1, Dec1, z1) and (RA2, Dec2, z2)]
I have Redshift (z), RA and Dec positions for two points in a galaxy catalogue (say P1 = [<...
- 151
5
votes
1
answer
924
views
Generating random galaxy catalogs for correlation functions
The galaxy correlation function, when computed directly from a galaxy catalog, relies on computing a randomly generated counterpart catalog.
When dealing with a simulated galaxy mock-catalog, where ...
- 193
5
votes
1
answer
294
views
How to remove redshift from galaxy spectra in Python?
Hello I extracted a spectrum from the central region of the 2D spectrum of the major axis from NGC 4697 (I just took a central row in the 2D data set, see this question for more information: How to ...
- 829
5
votes
0
answers
328
views
Generate probability skymap
I am trying to generate skymaps for a set of Fermi GBM triggers, containing the probability that a trigger originated in a given part of the sky. For each trigger, I have access to the RA, dec, error ...
- 51
4
votes
1
answer
267
views
Determining period of an exoplanet using radial velocity data
I've spent an incredibly large amount of time trying to wrap my head around how the period is computed using just solely the raw data for the radial velocity. I've tried my hand with some nonlinear ...
- 101
4
votes
1
answer
2k
views
How do I create a galaxy stellar mass function?
Suppose that I have an array of stellar masses of tens of thousands of galaxies, and that I also already know what the total "survey volume" is (in Mpc^3) within which all of those galaxies are ...
- 693
4
votes
1
answer
122
views
Different results for the same JPL Horizons query
On JPL Horizons website, I'm using the following query to get vector state for Earth:
...
- 73
4
votes
1
answer
398
views
Accessing SDSS server SQL server via python
Is there a way to directly access any of the Sloan Digital Sky Survey servers via SQL via Python?
Currently I have been able to run SQL queries from the website they provide (for example https://...
- 299
4
votes
1
answer
467
views
Using Einsteinpy to plot the precession of a star orbiting a black hole?
I am currently trying to code the precession of a star orbiting around a black hole, the issue I am having though is that I have no clue what the values are and what they mean in the code, if anyone ...
- 41
4
votes
1
answer
293
views
How to extract galaxy spectra for different radii in Python for spectra taken by long slit spectrograph?
I am trying to extract the kinematics from the elliptical galaxy NGC 4697 using the Fourier Correlation Quotient (FCQ) algorithm described by Bender (http://adsabs.harvard.edu/full/1990A%26A...229.....
- 829
4
votes
2
answers
2k
views
Eclipses with SkyField
I'm trying to compute solar eclipses for a long period of time, see Back-predicting solar eclipses
Initially, I wanted at several points on Earth whether an eclipse was visible at some point in time.
...
- 63
4
votes
1
answer
846
views
What is the 2D elliptical projection of the Celestial Sphere called, and how can I make one?
I see this kind of projection of the celestial sphere into 2D frequently, usually with an image of the milky way galaxy or cosmic microwave background. This particular image shows the path of visible ...
- 31.4k
4
votes
1
answer
146
views
Skyfield missing some rise and set dates
To compute the Andromeda Galaxy Risings and Settings I essentially use this code (in a more colplex code, but this serves the purpose):
...
- 55
4
votes
1
answer
69
views
How to build an adjacency matrix of stars connectivity from their physical kpc distances?
I'm probing into the Illustris API, and gathering information from a specific cosmos simulation, for a given redshift value.
This is how I request the api:
...
- 163
4
votes
1
answer
257
views
How can the IAU 2000A vs IAU 2000B nutation comparison be reproduced?
I am attempting to plot how the IAU 2000A nutation model degrades as its terms are omitted. As a spot-check, I decided to compare it to IAU 2000B, which includes only the 77 most important lunisolar ...
- 960
4
votes
1
answer
1k
views
Plotting Astronomical Data Using Python
I have been trying to create a graph which shows the distances between the stars and the earth, yet I could not obtain the desired graph as seen below (click to zoom in):
My graph:
As @uhoh ...
- 381
4
votes
1
answer
1k
views
Tests for code that computes two-point correlation function of galaxies
I'm currently writing a code to compute the two-point correlation function of a set of galaxies. As I work with a loooot of galaxies, it was suggested to me not to do it in real space, but to compute ...
- 193
3
votes
3
answers
2k
views
Python with image in fits format
I'm trying to write a Python program that will do the following: take an image in fits format and a reg file with a list of regions in the sky, and determine which regions in the list are inside the ...
- 133
3
votes
2
answers
241
views
Are 3D coordinate data from Sloan DSS-III available & easily accessible to non-pros?
Of course the newly announced SDSS-III data and maps from the Sloan Digital Sky Survey with 1.2 million objects, along with all previous data sets are openly available, and I'm sure there are many ...
- 31.4k
3
votes
2
answers
81
views
How to construct optimal Wiener Filter?
I am trying to construct a Wiener Filter, to filter the ratio of the peak from the cross-correlation function, between a galaxy spectra and a template spectra, with the peak of the auto-correlation ...
- 829
3
votes
2
answers
974
views
How to compute a Flux through a filter using SYNPHOT in Python
I am in the process of building an exposure time calculator to help nail down the exposure times I need for different targets in my observatory.
In amateur astronomy imaging, we use a filter called ...
- 106
3
votes
1
answer
1k
views
Query Gaia by star name
I am attempting to query Gaia programmatically in python to get certain properties for specific stars. I can write a query which obtains some properties, but only for all stars, not a set of stars or ...
3
votes
1
answer
141
views
Propagate Earth trajectory for 1 Myr
What is the most accurate way of propagation of Earth trajectory relatively to the Sun? I need to calculate the Earth-Sun distance. Is there any library on Python?
I've used before JPL Horizons, ...
3
votes
1
answer
76
views
Evaluating Potentials using Galpy
I am trying to model galactic disks. From the past research we have discovered that the halo follows the logarithmic potential, the disk follows the Miyamoto-Nagai potential and the bulge follows the ...
- 153
3
votes
1
answer
261
views
Can you get motion data using astropy.coordinates.get_body()?
I am trying to use get_body() to get position and motion data for solar system objects.
I’ve tried the following:
...
user44357
3
votes
1
answer
142
views
Lightkurve nan values after bin light curve
I am using lightkurve 2.0.2 library with Python 3.8.5 and astropy 4.2 for processing exoplanet transits. However when I want to bin light curve to fixed number of points, all values in ...
- 313
3
votes
1
answer
2k
views
How to plot celestial equator in galactic coordinates? Why does my plot appear "backwards"? [duplicate]
I'm trying to plot celestial equator in galactic coordinates. Here is my code (based on this answer):
...
3
votes
1
answer
335
views
Covariance matrix not calculated when fitting gaussians?
So I am using Astropy's basic models.Gaussian1D model and a fitter = fitting.LevMarLSQfitter() to fit 3 Gaussian pulses with some added random noise. The fit is good, but when I type
fitter.fit_info, ...
- 191
3
votes
1
answer
911
views
Orbital elements of solar system using Pyephem
I'm using the astrometric python module Pyephem, and I would like to get the orbital (keplerian) elements for the solar system planets.
The only values I found is the heliocentric latitude, ...
- 131
3
votes
1
answer
203
views
Open source library to calculate image from signals of a distributed set of radio dishes?
The National Radio Astronomy Observatory's Q&A "How To Make Images With a Radio Telescope" says
The most straightforward way to make a radio image with your satellite antenna system, ...
- 5,526
3
votes
1
answer
113
views
Galactic Equator zenith transit
I need to find the two times of zenith passage of the Galactic Equator for a given Earth Lat/Lon on any day between 3500 BC and 1500 AD. Since the Galactic Equator is a line and not a point, I try to ...
- 33
3
votes
1
answer
352
views
Need help with the math in Python program to flag Jovian radio emissions
A few days ago I decided to take on the little project of converting a Qbasic program into Python (as a side project to my Radio Jove project), and I've managed to get it to run, but the math is ...
- 133
3
votes
1
answer
87
views
How do I create well a weighted black hole mass function?
I'm running a set of simulations to study the evolution of Super Massive black holes.
In principle, I have the black hole masses and other property called merger tree weight in Mpc-3 unit which is ...
3
votes
0
answers
72
views
Keyerror: 0 while using astropy SkyCoord
I am facing a problem while using SkyCoord from astropy library. The scenario is as below,
I have read the data from a fits file into a pandas dataframe.
I have applied several quality cuts to the ...
- 153
3
votes
0
answers
71
views
Kolmogorov–Smirnov test p-value [closed]
I carried out a 2 sample Kolmogorov–Smirnov or "KS" test. I got a p-value of 0.11. That means the probability of 2 samples being of the same population is 0.11. Is it correct to say that the ...
- 194
3
votes
0
answers
62
views
S/N binning of 2D spectral galactic data
I have the 2D spectrum of the ellipical galaxy NGC 4697 taken by a long slit spectrograph. The x-direction (horizontal) corresponds to wavelength and the y-direction (vertical) corresponds to distance ...
- 829
3
votes
0
answers
155
views
Is there a tool to convert N-body RAMSES simulation file formats to GADGET 2 format in Python?
I am looking for a way to convert RAMSES files to GADGET-2 binary files because I want to use the package SimSpin (https://github.com/kateharborne/SimSpin/blob/master/R/make_simspin_file.R) which is ...
- 155
3
votes
0
answers
29
views
How to find x-values of fourier-transformed correlation functions in velocity space?
I am trying to extract the kinematic parameters (rotation velocity, velocity dispersion, ...) of an elliptical galaxy by extracting the kinematical broadening function using the FCQ-Algortihm first ...
- 829
3
votes
0
answers
576
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),...
- 409