Green object on DECaLS

http://legacysurvey.org/viewer?ra=359.0905&dec=0.4472&zoom=15&layer=decals-dr5&spectra

missing on SDSS

Pure-green objects mean they are bright in our “r”-band image, faint in “g” and “z”. Often this means something moving, since the g,r,z images are taken at different times. Usually these are asteroids.

I think this particular one is “1995 UQ18”
https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=90833
and we observed it on 2013-11-22 @ 01:29:23.4

cheers,
–dustin

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Thank you! I will check to confirm if it is this one. Why there is no other signature of this object in g and z band if it is asteroid? I saw several examples of asteroids with 3 dots close to each other for each of the bands.

Hi,

If you click on the map and then click the “Data” link in the popup, you’ll get this table of the images covering this part of sky:
http://legacysurvey.org/viewer/data-for-radec/?ra=359.0905&dec=0.4473&layer=decals-dr5
and you can see that the images are taken over the course of several years. Asteroids move a lot over that period, so this asteroid will be far away when we come back to take the g and z.

In SDSS, the different bands were taken within minutes of each other, and always in the same order, because of its drift scanning strategy – you can tell which direction the asteroid is moving!

cheers,
–dustin

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Ok, this helps a lot. Is there any viable strategy to search for slow moving objects with such constrains? I am just interested :slight_smile: