Color bar with values?

Dear Daniel,

sorry for having left your post unreplied. As Deborah explained, the all-sky maps available right now are just RGB representations of the data from given telescopes/surveys, created by combining different filters. You can find more information about how the colours have been assigned to the different wavelengths/frequencies/energies in our documentation. These maps are intended for quick visualisation and not to do science. However, we are working on a way to improve this visualisation, so that users can, for example, play with the image cuts. We hope to have more news on this in the near future.

Regarding your second suggestion, about the colour maps designed to accommodate colour-blind people, you may have noticed that our treemaps (which pop up when you click on the buttons to search for data) are now colour-blind friendly.

Cheers,

Belén

Dear Deborah, 

I hope ESASky is more than a pretty picture gallery.  The colors are meaningless if one doesn't know what is bright or dimm, and whether some color variation corresponds to much or little intensity variation.  So, as an option, it would be nice to be able to see on the side of the image the used colormap including a numerical scale.

 
Further the choice of the colormaps in ESASky is not optimal as the colormap are not  "perceptually uniform".  

There exists much better colormaps where the perceive intensity (brightness) for normal human eyes corresponds to the numerical value.  Such colormaps make interpreting pictures much easier.  I can refer you to the following article of Kovesi :  https://arxiv.org/abs/1509.03700
or the Matplotlib page explaining how to choose good colormaps: 

https://matplotlib.org/users/colormaps.htm

if you care about the ~5% of your visitors who are colorblind, there are even colormaps designed for them and others!

Otherwise thanks for this excellent tool !

Best regards,

      Daniel

Dear Daniel,

Many thanks for your suggestion. To help us, can you explain what you'd like to do with the colour maps (HiPS)? Please note that these maps are created more for quick visualisation rather than scientific usage, we recommend the user downloads and uses the FITS images directly for science.

Kind regards,

Debbie, on behalf of the ESASky team.