<p>You might find the <a href="https://ned.ipac.caltech.edu/" rel="nofollow noreferrer">NED</a> database and <a href="http://astrometry.net" rel="nofollow noreferrer">Astrometry.net</a> useful. NED is NASA's extragalactic database. You can search by a position in the sky with a radius and it will give you a list of known objects in that field.</p>

<p>Astrometry.net lets you upload images and will resolve what you're looking at, also giving you a list of known objects in your image.</p>

<p>I like to use <a href="http://cds.u-strasbg.fr/" rel="nofollow noreferrer">CDS</a> for a quick look up on objects. This will let you browse images from different surveys easily and links you to other sources on that object as well as publications about your object. </p>

CC BY-SA 3.0
2017-04-19T06:51:07.077Z
Do you have any idea how I could use image processing to classify different kinds of galaxies? I know that for elliptical galaxies, I can directly estimate the parameters of the best fit ellipse (to the contour) and get the eccentricity, thresholding on its value can give me a rough E0 - E5 scale. What about the other kinds? Also Do you know how to differentiate between stars and galaxies, given only image data? Not any other sensor/header data, but only image data?
astroman
CC BY-SA 3.0
2017-04-19T12:46:51.547Z
Please tell me how to use the NED, I cannot get it to give me the images!
astroman
CC BY-SA 3.0
2017-04-19T12:49:36.650Z
I get this when trying to do a search https://ned.ipac.caltech.edu/cgi-bin/OBJatt?delimiter=bar&nondb=row_count&crosid=objname&position=ra%2Cdec&enotes=objnote&position=pretype&position=z&position=zflag&attdat_CON=M&attdat_CON=S&attdat=attned&gphotoms=q_value&gphotoms=q_unc&gphotoms=ned_value&gphotoms=ned_unc&diamdat=ned_maj_dia&distance=avg&distance=stddev_samp&M=2524&M=2472&M=2872&M=2871&M=2992&M=2529&M=3000&M=3004&M=1019&M=1024&M=1029&M=1036&M=1040&M=1048&M=1052&M=1058&M=1061&M=1069&M=1072&M=1079&M=1081&M=2390&M=2425&M=994&M=996&M=998&M=598&M=1&M=1004
astroman
CC BY-SA 3.0
2017-04-19T12:50:38.237Z
Can you tell me how I could use the queries? Say I want an image of a region with only the count of ALL galaxies in that region, then save that image without any labels
astroman
CC BY-SA 3.0
2017-04-19T17:32:43.877Z
If you want to build some software then you might want to have a look at Astropy, I believe it has programmatic interfaces for querying databases like NED.
zeitoon
CC BY-SA 3.0
2017-04-19T17:33:16.240Z
As for that query you posted I think NED is glitching in that it's doing a logical AND by default. Try selecting one property at a time. Here's an example for just dwarf galaxies: https://ned.ipac.caltech.edu/cgi-bin/OBJatt?delimiter=bar&nondb=row_count&crosid=objname&position=ra%2Cdec&enotes=objnote&position=pretype&position=z&position=zflag&attdat_CON=M&attdat_CON=S&attdat=attned&gphotoms=q_value&gphotoms=q_unc&gphotoms=ned_value&gphotoms=ned_unc&diamdat=ned_maj_dia&distance=avg&distance=stddev_samp&M=2524
zeitoon
CC BY-SA 3.0
2017-04-19T17:36:36.900Z
Also your idea for elliptical galaxies is basically correct, if you want to classify spirals as well then learn how the Hubble classification works (Sa, Sb, SBa, SBb, etc.) https://en.wikipedia.org/wiki/Hubble_sequence

Stars can usually be distinguished from galaxies just by shape alone. You'll rarely find a spherical galaxy and foreground stars will often show up with bright crosses through them. Stare at a lot of images and you'll get a feel for it which you can then port to software. Software packages that do the sort of classification you want should already exist, but I dont know any.
zeitoon
CC BY-SA 3.0
2017-04-19T19:51:15.223Z
Thanks, but is there a database out there which gives me an image and tells me "there are X galaxies in here". I found galaxyzoo but I really dont see any image files in their data release
astroman
CC BY-SA 3.0
2017-04-19T20:37:57.840Z
But aren't E0 type galaxies spherical?
astroman
CC BY-SA 3.0
2017-04-19T21:14:09.120Z
Yeah, it sounds like you want to use Astrometry.net. You give it an image and it gives you a list of known objects in that field. You'll have to do some extra processing on that list to filter out anything that isn't a galaxy.

And yeah E0's are spherical, but its pretty easy to tell them apart from stars, at least visually. Galaxies will always be fuzzier than stars.
Like there's only around 8 galaxies in this image
http://www.sidleach.com/m89.jpg and a big E0 galaxy in the middle
zeitoon
CC BY-SA 3.0
2017-04-19T21:18:37.467Z
In general writing software that can classify galaxies just from an image is not easy and is not a solved problem, which is why you have things like galaxyzoo.
zeitoon
CC BY-SA 3.0
2017-04-19T04:56:18.473Z
2017-04-19T04:56:18.473Z
zeitoon
<p>I'm new to all this and trying to implement galaxy counting. For the initial stage <strong>I need raw image data, that is images with galaxies and stars along with a count of how many galaxies there are in the image.</strong></p>

<p>I came across this which seems to have a way to label galaxies </p>

<p><a href="http://skyserver.sdss.org/dr13/en/tools/chart/navi.aspx?ra=179.68929&amp;dec=-0.45438&amp;opt=" rel="nofollow noreferrer">http://skyserver.sdss.org/dr13/en/tools/chart/navi.aspx?ra=179.68929&amp;dec=-0.45438&amp;opt=</a></p>

<p><strong>but I cannot figure it out at all</strong>, I used this page </p>

<p><a href="http://skyserver.sdss.org/dr13/en/tools/chart/chartinfo.aspx" rel="nofollow noreferrer">http://skyserver.sdss.org/dr13/en/tools/chart/chartinfo.aspx</a></p>

<p>to try to get it to label only galaxies are seen but I got nothing (put G in opt section, did not make a difference).</p>

<p>Does anyone know how to operate the above or <strong>where I could get images with lots of galaxies (any number would do) in them along with a count of how many galaxies there are in the image?</strong></p>

<p>I found <a href="https://data.galaxyzoo.org/" rel="nofollow noreferrer">https://data.galaxyzoo.org/</a> but traversing it seems impossible</p>

<galaxy><data-analysis><photography>
I want a galaxy count database, also how do I use SDSS skyserver to fetch galaxies?
astroman
# I want a galaxy count database, also how do I use SDSS skyserver to fetch galaxies?

(Asked by: username_0 on 2017-04-18)

I'm new to all this and trying to implement galaxy counting. For the initial stage **I need raw image data, that is images with galaxies and stars along with a count of how many galaxies there are in the image.**

I came across this which seems to have a way to label galaxies

<http://skyserver.sdss.org/dr13/en/tools/chart/navi.aspx?ra=179.68929&dec=-0.45438&opt=>

**but I cannot figure it out at all**, I used this page

<http://skyserver.sdss.org/dr13/en/tools/chart/chartinfo.aspx>

to try to get it to label only galaxies are seen but I got nothing (put G in opt section, did not make a difference).

Does anyone know how to operate the above or **where I could get images with lots of galaxies (any number would do) in them along with a count of how many galaxies there are in the image?**

I found <https://data.galaxyzoo.org/> but traversing it seems impossible

**Tags:** galaxy, data-analysis, photography


---

## 1 answers

### Answer by username_1 on 2017-04-19. Score: 0 | Accepted answer

You might find the [NED](https://ned.ipac.caltech.edu/) database and [Astrometry.net](http://astrometry.net) useful. NED is NASA's extragalactic database. You can search by a position in the sky with a radius and it will give you a list of known objects in that field.

Astrometry.net lets you upload images and will resolve what you're looking at, also giving you a list of known objects in your image.

I like to use [CDS](http://cds.u-strasbg.fr/) for a quick look up on objects. This will let you browse images from different surveys easily and links you to other sources on that object as well as publications about your object.

> **Comments:**
> **username_0**: Do you have any idea how I could use image processing to classify different kinds of galaxies? I know that for elliptical galaxies, I can directly estimate the parameters of the best fit ellipse (to the contour) and get the eccentricity, thresholding on its value can give me a rough E0 - E5 scale. What about the other kinds? Also Do you know how to differentiate between stars and galaxies, given only image data? Not any other sensor/header data, but only image data?  
> **username_0**: Please tell me how to use the NED, I cannot get it to give me the images!  
> **username_0**: I get this when trying to do a search https://ned.ipac.caltech.edu/cgi-bin/OBJatt?delimiter=bar&nondb=row_count&crosid=objname&position=ra%2Cdec&enotes=objnote&position=pretype&position=z&position=zflag&attdat_CON=M&attdat_CON=S&attdat=attned&gphotoms=q_value&gphotoms=q_unc&gphotoms=ned_value&gphotoms=ned_unc&diamdat=ned_maj_dia&distance=avg&distance=stddev_samp&M=2524&M=2472&M=2872&M=2871&M=2992&M=2529&M=3000&M=3004&M=1019&M=1024&M=1029&M=1036&M=1040&M=1048&M=1052&M=1058&M=1061&M=1069&M=1072&M=1079&M=1081&M=2390&M=2425&M=994&M=996&M=998&M=598&M=1&M=1004  
> **username_0**: Can you tell me how I could use the queries? Say I want an image of a region with only the count of ALL galaxies in that region, then save that image without any labels  
> **username_1**: If you want to build some software then you might want to have a look at Astropy, I believe it has programmatic interfaces for querying databases like NED.  
> **username_1**: As for that query you posted I think NED is glitching in that it's doing a logical AND by default. Try selecting one property at a time. Here's an example for just dwarf galaxies: https://ned.ipac.caltech.edu/cgi-bin/OBJatt?delimiter=bar&nondb=row_count&crosid=objname&position=ra%2Cdec&enotes=objnote&position=pretype&position=z&position=zflag&attdat_CON=M&attdat_CON=S&attdat=attned&gphotoms=q_value&gphotoms=q_unc&gphotoms=ned_value&gphotoms=ned_unc&diamdat=ned_maj_dia&distance=avg&distance=stddev_samp&M=2524  
> **username_1**: Also your idea for elliptical galaxies is basically correct, if you want to classify spirals as well then learn how the Hubble classification works (Sa, Sb, SBa, SBb, etc.) https://en.wikipedia.org/wiki/Hubble_sequence  Stars can usually be distinguished from galaxies just by shape alone. You'll rarely find a spherical galaxy and foreground stars will often show up with bright crosses through them. Stare at a lot of images and you'll get a feel for it which you can then port to software. Software packages that do the sort of classification you want should already exist, but I dont know any.  
> **username_0**: Thanks, but is there a database out there which gives me an image and tells me "there are X galaxies in here". I found galaxyzoo but I really dont see any image files in their data release  
> **username_0**: But aren't E0 type galaxies spherical?  
> **username_1**: Yeah, it sounds like you want to use Astrometry.net. You give it an image and it gives you a list of known objects in that field. You'll have to do some extra processing on that list to filter out anything that isn't a galaxy.  And yeah E0's are spherical, but its pretty easy to tell them apart from stars, at least visually. Galaxies will always be fuzzier than stars. Like there's only around 8 galaxies in this image http://www.sidleach.com/m89.jpg and a big E0 galaxy in the middle  
> **username_1**: In general writing software that can classify galaxies just from an image is not easy and is not a solved problem, which is why you have things like galaxyzoo.  

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