Questions tagged [magnitude]

Questions regarding the brightness of objects in a defined passband.

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91 views

Is there a specific constant name for the fifth root of 100?

I understand that each scale you go up on the absolute magnitude scale, the luminosity decreases by the fifth root of 100, or around 2.512. Is there a name for the constant 2.512, or not. Also, is the ...
1 vote
0 answers
66 views

magnitude calculation if a blackbody's radius and temperature are provided

I know it is necessary to convolve its spectrum with the transmission curve of a filter. Are there any online tools or codes available for calculating a BB's magnitude in any specific band (e.g., ...
5 votes
1 answer
72 views

Query spectral type for absolute magnitude

I'm working on a project with stars where, given their spectral type (such as B0IV), I want to be able to know its approximate absolute magnitude. I have searched online and found data sources like ...
6 votes
1 answer
130 views

How to Determine Absolute Magnitude of a Galaxy using HST FITS Image

I'm attempting my first serious research project but due to... various circumstances, I am going to mostly be solving problems like this on my own with minimal outside help. As for the actual problem, ...
1 vote
1 answer
56 views

Visible angular size

Is it true that given two celestial objects of the same size and at the same distance, the fainter one will appear smaller? Is there a calculation that can be made about how smaller? Is it the same ...
0 votes
0 answers
44 views

converting rms to limit flux

My question is simple: if I have an RMS value (the standard deviation for my background) at 1 sigma, and I also have the zero point of my observation, how can I transform that value into the limiting ...
2 votes
2 answers
1k views

What is the difference between albedo, absolute magnitude or apparent magnitude?

What is the difference between albedo, absolute magnitude or apparent magnitude? I can’t really tell what’s the difference between them.
2 votes
1 answer
41 views

Standard definitions (ISO?) about subjects related to light emitted by stars

I'm a big fan of astrophysics and astronomy. However i'm quite confused by reading these last years plenty of books on the subject with various definitions (vocabulary) and notations for the same ...
2 votes
1 answer
156 views

Measuring magnitudes in ds9

I'm currently working on a project which involves measuring several Cepheids to determine the distance to a galaxy. I have been using 12 images from the Hubble telescope taken over a period of about a ...
0 votes
0 answers
101 views

Calculating the Flux density through different photometric filters

For a project I wrote the following python script for calculating the flux density. My question is: If the user enters for example magV = 22 and the user selects the B filter instead of the V filter ...
1 vote
0 answers
136 views

Photometry in SExtractor vs Python

I wanted to find stars in the dwarf Spheroidal (dSph) galaxy. I performed photometry using SExtractor and in Python using DaoStarFinder and other astropy packages. However, while extracting the ...
6 votes
1 answer
239 views

Sky surface brightness vs magnitude limit visibility

I am wondering how we can calculate the magnitude limit of the celestial object, which could be visible at the given sky surface brightness conditions. We already know that Venus and Jupiter are ...
1 vote
0 answers
50 views

Magnitude cuts in different bands/surveys

I have data on around 142,000 galaxies. Some of these galaxies have apparent magnitude data in different bands. For example, many of my galaxies have SDSS PSF data in ugriz bands,GALEX FUV, GALEX NUV, ...
2 votes
0 answers
47 views

What is the Chołoniewski method of estimating galaxy luminosity functions?

This paper describes a method to estimate the reddening of AGN using various methods, mostly to do with the intensity ratios of different absorption lines. It also mentions the Chołoniewski method, ...
7 votes
2 answers
444 views

Venus' magnitude during inferior conjunction

I was doing an assignment on Stellarium when I observed Venus to have an apparent magnitude that didn't become less negative than -3, even at inferior conjunctions when we faced the dark side of Venus....
4 votes
1 answer
304 views

Bolometric correction of the full moon

Now I am solving the problem about the transition from $V$ (= -13 in 400-700nm) to $m_{Bol}$. V is the full moon's apparent magnitude in 400-700mm(i.e., visible light), and $m_{bol}$ is the bolometric ...
2 votes
0 answers
48 views

General questions about SDSS

I'm considering doing research on SDSS spectral classification (STAR, GALAXY, QSO) with machine learning for my school dissertation. Not sure if this is an appropriate place for these kinds of ...
3 votes
1 answer
312 views

absolute magnitude of an asteroid

I've done some research and found that one could derive the absolute magnitude $H$ of an asteroid in the following way. $H$ is the brightness of the asteroid, observed on Earth, if the asteroid were ...
4 votes
1 answer
41 views

Visual magnitude - V_0 and V difference

Does $V_0$ stand for the magnitude during a primary eclipse and $V$ for magnitude during no eclipse? For instance, here is the magnitude of 2.41 and here the magnitude of 2.23. I saw the notation $V_0 ...
1 vote
0 answers
147 views

How to calculate absolute magnitude of planets?

Knowing: Star's radius $r_s$ , luminosity $L_s$, and absolute magnitude $V$ Planet's radius $r_p$ , albedo $a$ , and distance $d_s$ How can you calculate the absolute magnitude of a planet in a ...
2 votes
0 answers
30 views

Calculating absolute error in apparent magnitude of a star [duplicate]

I know that the apparent magnitude $m$ of a star is related to its intensity by Pogson's law: $m = −2.5 log_{10} I$. And I also know that the absolute error is defined as follows: Let $\hat{𝑥}$ be an ...
5 votes
1 answer
631 views

What's the brightest magnitude that the ISS can appear from Earth's surface?

Heavens-above indicates that this evening, it will fly almost over my head (79°) with a sizzling magnitude of -3.9. What is the maximum brightness it can have? Is there a formula to calculate its ...
6 votes
2 answers
2k views

How can I convert a GAIA-magnitude "G" to Johnson "V"?

Question: How can I convert the Gaia-magnitude G (and G_ESTIMATE) into a V-magnitude? The solution probably can be found in the Gaia Data Release Documentation for Gaia's EDR3 ("Early Data ...
1 vote
0 answers
99 views

Errors in photometric magnitudes from SDSS DR16

I'm playing around with the data in the SDSS DR16, but the magnitudes have huge uncertainties: ...
2 votes
1 answer
156 views

If Betelgeuse dimmed because of dust, what became of the dust?

This question started as a clarification request of a question from Glorfindel, answered at least in part by James K, and I realized it would probably be best as a stand-alone question. The most ...
3 votes
1 answer
169 views

On finding the magnitude of Stars

I am wondering how I would be able to predict the Magnitude of fictional stars, given we know enough about them. As the formulae I can find online are mostly getting overly high values that don't seem ...
5 votes
1 answer
1k views

A question about stellar magnitude and the pogson's equation

Well surely the eye has different sensitivity to various wavelengths... Will the Pogson's equation not be affected if say I compare Betelgeuse and Rigel (both having a marked difference in spectral ...
9 votes
1 answer
842 views

Superscript-subscript uncertainty notation

While reading publications in astrophysics I've encountered this kind of notation (fictitious example): $$M = 6.1^{+0.6}_{-0.1} \times 10^{30} \textrm{ kg}.$$ Several examples are here, p. 2. I assume ...
4 votes
1 answer
111 views

Is there a difference between Vis and V when analyzing the magnitudes of stars?

I have a dataset of a binary star system's magnitudes taken over the past decade, obtained from AAVSO. These magnitudes are reported in B,V,R,I, and so on. Some magnitudes have their V magnitudes ...
4 votes
2 answers
354 views

Can you subtract magnitude of constant source to get magnitude of variable source?

Let's say I observe a source that is actually two sources (source A and source B) where each cannot be individually resolved. Source A is a variable source and source B is a constant source. I want to ...
0 votes
1 answer
118 views

Question about calculating the ratio of volumes of two components of an eclipsing binary star

I'm trying to solve this task: At the maximum, the eclipsing binary star has a brightness of 6^m, and at a minimum of 8^m. Considering the eclipse to be central and the companion to be dark, find the ...
2 votes
1 answer
46 views

Proper way to average a set of color measurements?

Say we're given a set of flux measurements in two filters for a group of $n$ stars, say H-band and K-band: $F_H$ and $F_K$ From these, we can compute a color in $\Delta m$ for each of the $n$ stars, e....
2 votes
0 answers
70 views

starting from SSP spectra to evaluate galaxy spectrum and observed mag

I know that the galaxy spectrum, namely the flux per unit wavelength versus the wavelength, is the sum of the Simple Stellar Population (SSP) spectra at a fixed redshift (e.g. similar to eq. 1 in ...
1 vote
0 answers
43 views

What magnitude stars are visible during a quarter moon, during nautical twilight?

Assuming I'm looking for stars at least 50° from the quarter moon, is there any way to determine what magnitude stars would be visible to the naked eye, in a sky without light pollution, during ...
5 votes
1 answer
354 views

Naked-eye limiting magnitude: mismatch between Wikipedia, online converter and Shaefer's formula

I'm trying to make sense of the difference between the reference Sky Quality Meter (SQM) readings given in the Wikipedia article on Bortle scale, online converters like [1] that are based on Shaefer's ...
1 vote
2 answers
94 views

Why is magnitude of Beta Lyrae given as 30.0 in Henry Draper catalog?

Beta Lyrae (HD 174638) is ascribed visual magnitude 30.0 in the Henry Draper catalog. There are hundreds of other stars in the catalog also given magnitude 30.0. What was meant by these nominal ...
3 votes
1 answer
133 views

How is the difference of bolometric magnitudes not dependent on the stars' radii?

The difference of 2 bolometric magnitudes is given by: $$M_{bol, ★} - M_{bol, ☉} = -2.5 \cdot \log \left( \frac{L_★}{L_☉} \right)$$ But Pogson's equation is: $$M_{bol, ★} - M_{bol, ☉} = -2.5 \cdot \...
4 votes
1 answer
2k views

Conversion of magnitudes to Jansky and MAGPHYS?

I'm a bit puzzled and not an observer, so please bear with me if I'm being stupid here. The code MAGPHYS specifies Jansky (Jy) as the input unit for flux through ...
2 votes
2 answers
305 views

Position of a star on the HR diagram

Does the position of a star on a HR diagram depend on the magnitude system/color index used? I made a CMD of a particular cluster using HST WFC3/UVIS data, and when I plotted $F275W vs F275W - F606W$...
2 votes
2 answers
680 views

Formula to calculate the apparent magnitude of Earth from arbitrary distances

I would like to calculate the apparent magnitude of Earth from various distances, say from the Voyager probe at this moment or from various stars in the sky. I know there must be a formula that I can ...
5 votes
1 answer
434 views

How do you carry errors for brightness magnitudes [duplicate]

I have a value for the relative flux $F_2/F_1$. With some uncertainty value $a$. If I use the equation to get relative magnitude: $m_1 - m_2 = 2.5 \log_{10}(F_2/F_1)$ How do you now calculate the ...
0 votes
2 answers
95 views

Vmag versus VpgMag in GSC 2.3 catalogue

I tried to find out the magnitude in V for V* V881 Per. Here are my results: SIMBAD: $11.09$ (Fluxes->V) GSC 2.3: $10.9815$ (VpgMag) and $10.887$ (Vmag) Which of VpgMag or Vmag in GSC 2.3 ...
3 votes
1 answer
1k views

When does a solar eclipse become noticeable?

For a human viewer located on Earth, is there an approximate apparent magnitude at which a solar eclipse becomes apparent in the form of a noticeable change in ambient brightness? Assume normal ...
3 votes
2 answers
202 views

Graph of apparent magnitude of Mars through time from around 2000 to present?

I tried to search online but failed to find a graph of the apparent magnitude of Mars over time from 2000 to present. From Wikipedia: Mars made its closest approach to Earth and maximum apparent ...
0 votes
0 answers
28 views

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 ...
3 votes
1 answer
201 views

How to derive the depth in my image (limit Magnitude )?

I saw that some survey said that their depth is 27.5 magnitudes. May I ask that if I have a dataset with magnitude and their errors, for example I have J band j_m, <...
1 vote
0 answers
138 views

Binned of phase-folded light curve

How I can bin a magnitude phase-folded lightcurve? I take mean values magnitudes and it's uncertainties but this is wrong.
2 votes
1 answer
171 views

Converting Light curve to Luminosity

So I'm currently working around a specific variable star, α Ori and I want to determine it's luminosity...I do only have the light curve (driven from V-optical photometric band - Johnson V from AAVSO)....
1 vote
1 answer
83 views

Why is SWAN dimming?

The SWAN C/2020 F8 comet is passing near the Earth, but from Wikipedia The comet has dimmed a small amount since May 3. It was expected to possibly reach 3rd magnitude in May, but is now expected to ...
3 votes
0 answers
717 views

Conversion of Magnitude to flux using zero point in AB Magnitude

I want to calculate the flux of the 5 sigma limited magnitude. It is given that the zero point magnitude of NB964 is 28.77 and 5sigma magnitude is 25.45. The following example is from A large, deep ...