HSC DR2 dates

How do I get the date for a HSC DR2 image please? It is needed to help identify when a possible transient is first observed.


For HSC, I only have the coadds, not the individual images. I have not queried their database to get the full list of exposures that went into the coadds, so I don’t really have that information available.

For this one, if you flip over to the SDSS image, you’ll see that this green thing is moving quickly!


Thankyou for your reply. It is unfortunate that the data cannot be accessed as at least a couple of transients could be given the yes or no if the dates were known.

As for the object moving, we argue that the SDSS pic (more than 10 years earlier) has an artifact in it. Please see the Galaxy Zoo website for more relevant info:
Subject 36250950

We see it in the Legacy Surveys DR8 images too; it’s real.

PS, you should look into the HSC DR2 pages. The raw images certainly are available, so it should be a matter of navigating their database structures to figure out which raw images are included in the coadd for a given place on the sky. I just haven’t done that for the viewer.

So, amusingly, in the Legacy Surveys we have several exposures there from different nights, and we only see it in exposures from one night – 2 each in g and r bands. It does not correspond to a known asteroid in the JPL horizons system.

AND, in SDSS there are two exposures of that chunk of sky, and it only appears in one of them!

Varying, 250 mas/yr mover?!


There used to be a very handy Data link in the Legacy browser to the various SDSS frames. We found several transients by using this link, but now it’s gone or doesn’t work.

Pan-STARRS is inconclusive… Marco Kovic and Ine Theunissen: experienced transient hunters… The SDSS pic is from 03/05/2002…

This DR7 link has four exposures over 5 minutes in the g and r filters:
observed 2016-01-16 @ 05:12:04
observed 2016-01-16 @ 05:13:30
observed 2016-01-16 @ 05:16:04
observed 2016-01-16 @ 05:17:12

The difference between SDSS and DECaLS is a few pixels in position but 14 years in time. It is not present in cutouts from April 2015 or March 2016, which leaves enough for a transient to explode and then fade away.

An SDSS photographic anomaly… If we could access the HSC dates, it would be a welcome addition.


Figuring out the HSC dates will involve querying the database here.


You can check out this CSV – I think it lists the HSC images there.

Thanks again for your help. I have tried many times to register with HSC but it has yet to accept a username from me. I will keep trying or plead with someone who does have access. Best

We managed to track down a time and date for the HSC object after eventually getting registered. There is a new image on the Galaxy Zoo website from HSC and the welcome information:

HSC Frame data for coords 137.771514, 4.645482 R filter
taiobs=2016-02-08 10:07:53.951

which fits nicely into the timeline.

Yeah, so you’re right, I now believe the green blob in the SDSS image, 2.5 arcsec away, is actually just an unmasked Cosmic Ray in the r-band image in run/camcol/field 3015/2/158 – see attached plot of the SDSS g/r/i bands.

By the way, you can get the list of SDSS images by turning on the “SDSS CCDs” overlay, which then gives you a link to the individual images.

And for HSC, it looks like there are 5 exposures in g on 2016-03-07
and 5 exposures in r on 2016-02-08. I didn’t check other bands, and I’m not certain that all 5 of these exposures actually contain that galaxy.

Anyway, this now just looks to me like a plain old supernova.


I’m glad you agree with our findings. It has been reported as AT 2016jje