Questions tagged [units]
Use for questions about standards of measurement used for different types of quantities, and for conversions between units.
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Correct units to use while plotting mollweide projection of sky chart with RA and Dec values, matplotlib
I am trying to plot a mollweide projection of a sky chart in Python using the matplotlib package. I am using the RA and Dec values from a database containing all stars in Hipparcos, Yale Bright Star, ...
user30617
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How to convert from Black body intensity to MJy/sr?
How does one convert from ${\rm ergs\cdot cm^{-2}\cdot s^{-1} \cdot sr^{-1}\cdot Hz^{-1}}$ to ${\rm MJy \cdot sr^{-1}}$
and from ${\rm ergs\cdot cm^{-2}\cdot s^{-1} \cdot sr^{-1}\cdot cm^{-1}}$ to ${\...
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Neutrino Modelling in Friedmann Equation
I'm trying to model neutrinos in the Friedmann Equation. I've covered the case of the Benchmark Model where we have matter, radiation, curvature, and the cosmological constant, Lambda. I know my ...
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How to convert apparent visual magnitude to SI units?
How do I convert the apparent visual magnitude of astronomical objects to SI units (lumens)?
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How to convert from FELO-HEL to Km/s?
I am using DS9 to calculate the rotational velocity of a galaxy. I have 21cm cube and I used DS9 to plot this graph
I do not understand what is FELO-HEL! and I want to convert the units from FELO-...
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What is "g-98" in plots of stellar spectra?
I was looking to find some example carbon star spectra and came across this page on the Harvard website which shows several plots of carbon star spectra. The horizontal axis is labelled as wavelength ...
user24157
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What does it mean when there are two plus-or-minus signs for a measurement?
As far as I know, the plus-or-minus sign is used to indicate the statistical margin of error of a measurement. But what does it mean when there are two plus-or-minus signs in the same measurement?
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Conversion factors for flux
I have a flux value in the infrared band of 8 mJy at a wavelength of 80 microns that I want to translate into X-ray conventional ...
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A "strange" unit radio astronomy
I'm reading up on radio astronomy, and I came across this paper from 1964. At the bottom of page 193, the author uses a unit that I've not seen before in discussing radio power emission from stars:
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Conversion of UBVRIJHK magnitudes to luminosity?
So, I know that the standard for conversion from bolometric magnitude to luminosity established in 2015 equates to:
L = 10^(-0.4 * magnitude) * 3.0128e28
Easy ...
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Units in optical and radio spectral data cubes: Flux vs Brightness
I have noticed that the units used in spectral data cubes coming from optical IFU instruments are usually in $erg/s/cm^2/Ang/pixel$. To my understanding this is a measure of Flux. Right?
However, in ...
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Converting Jy/beam to Jy?
Maybe its a dumb question, but to convert Jy/beam to Jy, I just have to multiply it by the beam size in sr right?
Being $\Omega$ the beam size:
$\Omega = \frac{\pi \theta_{maj} ~~ \theta_{min}}{4 \...
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Finding the radius of a star in arcsec
If i know the radius r of a star in cm, how can I convert it to arcseconds?
For example, if I have a star with r = 3.18e13 cm, and distance to the star d = 220 parsecs, what is the relation to ...
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How to convert density from physical unit to comoving unit?
I am learning co-moving units and I am interested to see how the conversion works. If Hubble constant is assumed to be 0.7, then I want to convert $1gm/cm^3$ into comoving unit. If I want to express ...
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Units of integrated flux density (irradiance) along longitudes
If I've taken an image of the Galactic bulge with the pixel units in MJ per steradian:
and I've looked down each column of the image and added up the values:
then do the units change? My thinking is ...
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