Images are sometimes not correctly centered

[OlivierMarchal]

Some users of the Jafar website have noticed that some objects are not correctly centered. It is like as if a vertical offset was applied. But this offset is not systematic and not constant : sometimes the centering is ok, sometimes it is not.
Also this issue does not happen for Mac users, it seems to happen only for Linux users (to be confirmed). Which means it is very difficult to reproduce...

Here is an example of badly centered object. The dwarf galaxy is correctly centered for users using macbookpro.
The resolution of the screen showing this issue is 1920x1200.
The coordinates of this objet are :
269.53707, 66.192977

But the object located at 272.192917, 65.969009 is correctly centered.

The jafar website is currently using https://aladin.cds.unistra.fr/AladinLite/api/v3/3.4.5/aladin.js.
In terms of javascript code, I am just doing this:
aladin.setFoV(fov);
aladin.gotoRaDec(ra, dec);
I checked that the fov and ra/dev values are correct and that the values transmitted to aladin are the same for the different users. So it is not a truncated value issue at my level.

We have tested different coordinates systems, different zoom values, different projections, but it does not help.

We also tested different versions of aladin. Version 3.3.2 is working but 3.4.2-beta already shows the issue. So a modification between those 2 versions seems to be cause of the problem.

[bmatthieu3]

Is there other examples of sources/objects whose coordinates are not centered ? If so can you can the list of non matching coordinates ?
Did you test or are you able to test with a more recent version of aladin ?

[OlivierMarchal]

This issue happened during the validation around of 4000 objets, and I cannot provide a full list because it would mean to inspect again every object one by one.
In the comment above I said I tested with version 3.4.5 because it is the latest stable version in https://aladin.cds.unistra.fr/AladinLite/doc/release/.
And I cannot use 3.6.0-beta contains a bug related to the cuts (they are not applied any more).

But if there is a more recent stable versions, I can ask the users to make a test.

[OlivierMarchal]

We did more checks on our side.

• the bug appears between the following versions 3.4.1-beta and 3.4.2-beta. So now you have 2 consecutive versions of aladin, which will facilitate the investigations.

• Other coordinates which show the problem :
  270.334079 , 66.730469
  268.695381 , 66.316203
  271.001157 , 65.978373

• here is a screenshot of the aladin div. We have the same with or without the bug:

[OlivierMarchal]

An other user saw the issue on mac. So it is not related to linux as suggested above.
" I had offset problems with:

• macbook pro, macOS 14.6.1, Sonoma; Tried with Firefox, Safari, Chrome and Opera browsers;
• macbook pro, macOS Ventura (not sure about the specific OS version); Tried only with Firefox

I had not offsets problem with Safari on:

• iPad pro 12.9, iPad OS 17.7.2
• iPad pro 11, iPad OS 18.1.1
  "

[ManonMarchand]

And I cannot use 3.6.0-beta contains a bug related to the cuts (they are not applied any more).

Is there an open ticket about this? I did not find it

Edit: #225

[tboch]

I think this issue could be linked to #193

[bmatthieu3]

I was able to reproduce it I think with the position 270.334079 66.730469. It seems the radec2xyz on single precision float adds that offset for lat that tends towards the poles. I now perform it on double and it looks centered on my configuration.
I am not sure #193 targets the same problem or more precisely I am not sure it is totally linked because there may also be for that case (big fov) the need to subdivide more the cells in the view. Still it cannot do bad things for that case too.