Under review

Double HST Images

Pedro Gómez Alvarez 1 year ago updated by Deborah Baines 2 months ago 6

Sometimes HST Images appear as double images. Not sure if they are two images with different WCS or the same image repeated.

For example see HST ACS at 10:01:20.78 +55:53:49

Screenshot attached

Dear Ming Yang,

We are working with the HST archive team to produce better HiPS (Hierarchical Progressive Survey) images - the background all sky images in ESASky (and the image above). We are also working on loading a fits onto the sky, in exactly the region that it falls compared with the background sky. This would also solve the above problem of seeing double images. 

We'll announce when we have these ready. 

Many thanks and regards,


I think the new version of HLA image (DR10.1) should be much better, since the astrometric calibration is based on the Gaia DR1 and most of the image misalignments have been fixed

Dear Pedro,

this is due to the overlap of images of the same sky area to create the all-sky maps. HST has such good resolution that just a tiny difference in the WCS creates this effect.  Unfortunately, this is difficult to correct in an automatic way when generating the maps.

We have a long-time pending task to improve and update these maps. We will then explore new ways of tackling this problem.



Thanks Belen that makes sense, in this case it would be useful being able to select which images are displayed, which would alleviate this problem and would give an additional degree of freedom to the user. 

Fell free to ignore this suggestion, since it would probably complicate the design...

Congratulations for this service! 

I don't think this could be done unless the maps are generated on the fly, which is unfeasible due to the long computation times... But I'll take note of your suggestion to discuss it with the developers.

Thank you,