Galaxy images

Dear Legacy Survey team.

Can I get galaxy images from all the bright galaxies (HyperLEDA) in DECaLS DR10?

I want just the image in grz. and the image size is about 768px. The images sliced by “ra” slices in degree. Do not put the galaxies in just one folder, but all in the ra slice.

Like this.

000
----image
----image
----image

Not this.

000
----Galaxy
--------image

If so, thanks.

Isn’t HyperLEDA like 10 million galaxies? That’s… kind of a lot of cutouts to make.

HyperLEDA has only over 3 million galaxies to make. Should not be 10 million galaxies.
And it should only be visible in DECaLS DR10. Maybe 2 million?

2 million images x 768 pixels^2 x 3 bands x 4 bytes/pixel = 14 TB of FITS images… which is a fair fraction of the whole DR10 data release size :slight_smile:

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I did some SDSS RGB image cutout downloads using excel VBA script (then use a Photoshop script to find particular rgb pixels) in the past as my ultimate attempt at building my own Frankenstein steampunk Voorwerpje finding engine :rofl: (worked perfectly but failed miserably at finding only Voorwerpje coloured pixels)

So I have an inkling of the time it takes to download (and correctly name / file) such a dataset

Aside from here you only have FITS files and still need to create good RGB images and store those :open_mouth:

I’d say fire up the modem asap cause you might be waiting for a while….

What about you give me the download to all the HyperLEDA/SGA galaxies in the DECaLS DR10 foorprint and the MzLS+BASS footprint. Try to avoid the “Group Catalog” where you grouped 1,825 galaxies into one image. The number of galaxies will be split into one image at a time. Please include the name of the galaxy a seprate image, thus in the center of the image.

Try to use the image format in image size 256 by 256 pixels. The cutout size is about 13 kb in .jpg format. There would be about < 759,000 total images, around 2000 galaxies in each folder in 359 ra degrees, with low numbers (<1000) where there is less data in the DR10 footprint.

I have tried to limit the image size to try to make the files way less than < 2TB.

Hi,

You can also create your own cutouts (in JPEG or FITS format), with a URL like
https://www.legacysurvey.org/viewer/cutout.jpg?ra=71.0757&dec=-41.4322&layer=ls-dr10&pixscale=1.00

(plug in your own ra=, dec=, pixscale= values…)

cheers,
dustin

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If only things were ever that easy

Try using Dustin’s suggestion of applying the link and try to create something out of it that does what you want it to do, that’s how everyone gets their things done in the citizen science field

But I suspect that for what you want to achieve you’ll probably have to resort to some smart coding, in SIMBAD TAP service or something similar

Good luck with your quest

I did not say that you apply cutouts. since it takes longer than I thought for 1 degree. You would have to enable HyperLEDA/SGA galaxies in order to turn this on. searching takes like about 20 seconds, and downlading the cutout takes like 10 seconds. That takes approximately <1 week to download.

However there are images at the sga.legacysurvey.org site that contain 328,787 galaxies but it is only in the LS DR9 footprint. 328,787 galaxies in the image only (no models/residuals) All montages = <200kb, image only is divisible by 3 which may be 67kb, with images size 256x256 pixels wile bump the sizes way down between 10-20kb. The _GROUP files would be edited and I can add other galaxies in the DR10 footprint that could also be added. With these images in the DR9 footprint, that would save me much time.

The SGA montage image files are at URLs that are easily to compute based on the contents of the SGA catalog, eg
https://portal.nersc.gov/project/cosmo/data/sga/2020/html/000/PGC000010/PGC000010-largegalaxy-grz-montage.png
so if you wanted to script up downloading them, that would be an option.

When I look in the 000 RA slice, I see that those montage files are a total of 890 MB.

cheers,
dustin

I just want the images only, no models or residuals. No montage files also. It is found in

Like I said above, i want a file in .zip or .tgz format. I don’t have a script application unfortunately, so it maybe up to you…

I’m confused a bit

What is up to who precisely?

Hello, Dustin
Have you have updates about the images yet?

I made a tgz for the RA = 0 slice – https://portal.nersc.gov/project/cosmo/temp/dstn/000.tgz – have a look and see if that will work.
cheers,
dustin

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Sorry, like I said above, I do not want it in organized by folder, the images in one folder. (sorry)
Please read the first comment.

You can do this with a simple “move” command after unzipping it, whereas doing it at zip time isn’t trivial. Sorry, but there’s only so much time I can devote to individual requests.
–dustin

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How do I actually use the ‘move’ command?

On linux you could do

tar xzf 000.tgz
mv 000// 000/

to move all the images into the 000 directory. That will leave all the directories there, so you could remove them with

rmdir 000/*

(which will complain about the images, but harmlessly)

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