All Questions
14,956
questions
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SNR (Signal to noise ratio) from image
I have JWST images across 7 filters. I extracted sources by using SExtractor. How can I estimate the SNR of each source in each filter. Should I use flux/flux_err or use flux/background_rms. (flux and ...
- 51
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3
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Using EAZY as photometric redshift estimation tool
I am new to JWST data analysis and currently trying to extract redshift of high redshift sources from the catalogue I created from SExtractor. I'm using EAZY (Brammer et al. 2008) for this purpose.
I ...
- 51
-6
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53
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Answer this or don't downvote
Otherwise you'll be showing your complete ignorance in the matter and contempt for the truth.
If the scale factor as a function of time represents or is equal to the average distance between the ...
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23
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Is there any astronomical phenomenon such that its movement can be perceived in real time?
Note: I think I could make this question more interesting by asking, "What is the phenomenon at greatest distance from Earth such that its movement can be perceived in real time?"
My ...
- 143
1
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23
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Why is there a discrepancy between the difference in ecliptic longitudes as found with Skyfield when accounting or not accounting for precession?
I'm using Skyfield to calculate some ecliptic longitudes for various dates. I understand that the 0° point of ecliptic longitude changes based on precession due to being the intersection between the ...
- 255
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Why is there a discrepancy between ecliptic longitudes found with Skyfield and Astrolog for old dates?
Just to preface this, I know that Astrolog is software meant for astrology, which is pseudoscientific nonsense; however, I have a friend who insists on using it for certain astronomical calculations (...
- 255
3
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21
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How did the Local Interstellar Cloud form?
The Local Interstellar Cloud (LIC) is a low-density interstellar cloud which embed the Sun and other stars.
How did this region form? I suppose a supernova or stellar winds from multiple stars may ...
- 365
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14
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Hour angle to Right Ascension correct when the longitude is positive
I'm developing a Astronomical software using the formulas from the book: "Practical astronomy with your Calculator and Spreadsheet", but I'm having some problems to get the right ascension ...
- 657
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33
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What would sunsets look like around different star types?
I have always wondered what a sunset would look like around different types of stars. I have tried to do some research into the types of light refraction, but I cannot find any answers anywhere, and ...
- 83
6
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52
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Historically, when were the terrestrial planets first called terrestrial planets?
When did we start using the phrase "terrestrial planets" to refer to the inner planets in English scientific writing?
- 61
1
vote
3
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105
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Does the spacetime interval metric define spacetime as necessarily anti desitter?
N-Lab says:
We may define the anti de Sitter space of signature $(p,q)$ as isometrically embeded in Space $\mathbb{R}^{p,q+1}$ with coordinates $(x_1, \dots, x_p, t_1,\dots,t_{q+1})$ as the sphere $\...
- 1,250
4
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1
answer
89
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Required temperature for a nova
On the wikipedia page of the nova is said that the CNO cyle, which converts hydrogen into helium, starts on the surface of the white dwarf when the temperature reaches about 20 million K.
My question ...
- 365
5
votes
1
answer
734
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What does HJD-2450000 mean?
I've been looking at the OGLE Collection of Variable stars for the purposes of making a machine learning model to classify variable stars by their plots. In each variable star, I see the following ...
- 825
11
votes
2
answers
2k
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Always orient a sundial towards polar north?
I had a horizontal sundial made specially for my latitude (approx. 38° N). The default correct way to orient a sundial (in the northern hemisphere) is with the gnomon pointing towards polar north. The ...
- 221
2
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0
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47
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Do there exist open-source implementations of non-SGP4 propagators?
I'm well familiar with SGP4 and its implementations in various languages. I am curious if there are open-source implementations of J2Mean, J2, J3, J4, etc propagation techniques.
If my terminology is ...
- 566