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Number of stars by magnitude

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#1 Joko

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Posted 08 December 2023 - 02:54 PM

Hello,

I am looking for a file or an internet link indicating the number of stars for a given magnitude (mV).

For example, how many stars are visible up to magnitude 8. Same for mV 9, 10, 11, 12...

If you have any info, I'd be interested.

Thanks


Edited by Joko, 08 December 2023 - 02:55 PM.


#2 ismosi

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Posted 08 December 2023 - 03:43 PM

This only goes to mag 10

https://en.wikipedia...arent_magnitude

 

Or this

http://www.stargazin...wmanystars.html


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#3 dmclouse

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Posted 08 December 2023 - 06:34 PM

check http://www.stargazin...wmanystars.html


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#4 Joko

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Posted 09 December 2023 - 04:41 AM

Thank you, this is exactly what i was looking for.

 

 
 

 

 

 

 
 

 

 


Edited by Joko, 09 December 2023 - 04:42 AM.


#5 Tony Flanders

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Posted 09 December 2023 - 07:14 AM

I don't trust the second of those beyond 10th magnitude, since it's based on the assumption that the number of stars continues to grow at the same rate above (fainter than) that limit as under it. There are many reasons why that might not be true.

 

Also, it's definitely not the case that the curve of star density versus limiting magnitude is the same in all parts of the sky. It's one thing when you're viewing at right angles to the plane of the Milky Way, so that you run out of stars quite fast after a couple thousand light-years, and another thing entirely when you're viewing the Great Sagittarius Star Cloud, most of whose stars are tens of thousands of light-years distant.

 

We now have excellent photometry of all stars down to 14th magnitude, and GAIA goes down to around 20.0, albeit with a non-standard photometry system. It would be interesting to plot the actual distribution using actual data.


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#6 gwd

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Posted 09 December 2023 - 10:14 AM

I don't trust the second of those beyond 10th magnitude, since it's based on the assumption that the number of stars continues to grow at the same rate above (fainter than) that limit as under it. There are many reasons why that might not be true.

 

Also, it's definitely not the case that the curve of star density versus limiting magnitude is the same in all parts of the sky. It's one thing when you're viewing at right angles to the plane of the Milky Way, so that you run out of stars quite fast after a couple thousand light-years, and another thing entirely when you're viewing the Great Sagittarius Star Cloud, most of whose stars are tens of thousands of light-years distant.

 

We now have excellent photometry of all stars down to 14th magnitude, and GAIA goes down to around 20.0, albeit with a non-standard photometry system. It would be interesting to plot the actual distribution using actual data.

Is this excellent photometry of all stars down to 14 magnitude available to download?  A decade or so ago I downloaded a merged Tycho2 file called All-Sky Compiled Catalogue of 2.5 million stars".   The GAIA data needs to be mapped to the other data sets so the photometry is comparable.  

 

Here are the results of a simple query on the All-Sky Compiled Catalogue "VMAG" column:

"mag","count"
-1.0,1
0,13
1,36
2,126
3,365
4,1151
5,3540
6,10874
7,31226
8,87467
9,235283
10,607644
11,1062815
12,435394
13,22756
14,1865
15,69
16,1
99,687

 

99 of course is a no-data number.  You can see the regularity of the count progression ceases after 11th magnitude.   


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#7 Tony Flanders

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Posted 09 December 2023 - 05:04 PM

Is this excellent photometry of all stars down to 14 magnitude available to download?  A decade or so ago I downloaded a merged Tycho2 file called All-Sky Compiled Catalogue of 2.5 million stars".   The GAIA data needs to be mapped to the other data sets so the photometry is comparable.


You might start with APASS. Be aware that dealing with gigantic astronomical catalogs isn't always easy.
 

Here are the results of a simple query on the All-Sky Compiled Catalogue "VMAG" column:
"mag","count"
-1.0,1
0,13
1,36
2,126
3,365
4,1151
5,3540
6,10874
7,31226
8,87467
9,235283
10,607644
11,1062815


These numbers hint that the catalog is likely more or less complete to magnitude 9.5, pretty good to magnitude 10.0, and then becomes increasingly spotty. That's why there's a slightly less than three-fold increase per magnitude up to 10.0, but just a 75% increase from 10 to 11.
 
Back when I was plotting star maps for Sky & Telescope, I never trusted Tycho 2 past 10.5. I always did mean to make a deeper star database for the plotting program using UCAC4, but as I said above, dealing with astronomical quantities of data isn't for the faint of heart.

Edited by Tony Flanders, 09 December 2023 - 05:08 PM.

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#8 AstroVPK

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Posted 10 December 2023 - 10:01 AM

Try using TopCat or AstroPy - might be slightly easier. Tycho2 is manageable but Gaia is just enormous!
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#9 gwd

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Posted 23 December 2023 - 08:21 AM

Try using TopCat or AstroPy - might be slightly easier. Tycho2 is manageable but Gaia is just enormous!

What I don't like about Gaia is I don't have a good way to merge it with Tycho2 or whatever and Gaia isn't a superset of Tycho2.  The Tycho match files aren't exact so.... like other's said those astronomically large astronomy databases aren't for the faint of heart.   What I really like about Gaia is the query capability so I can download subsets of interest and not the whole darn thing.  




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