# Questions tagged [magnitude]

Questions regarding the brightness of objects in a defined passband.

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### 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
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., ...
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 ...
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
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 ...
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 ...
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.
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 ...
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 ...
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
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 ...
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
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, ...
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, ...
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....
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 ...
48 views

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 ...
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 ...
41 views

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 ...
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 ...
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 ...
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
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.
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