Added markers for sources with gaia XP spectra

[Alex-J-Brown]

I've been thinking that some of the issues we have with flux calibration (mainly with HiPERCAM where you're lucky if there's a flux standard observed in the same night) may be helped by having comparison stars with Gaia XP spectra that can be used for synthetic photometry within the same field and therefore removing issues with related to having to fit the atmospheric extinction too.
I plan to add XP spectra calibration to my cam_cal package at some point in the future once I work out how to properly use the XP spectra i.e. standardising them and testing the u-band stuff (and find the time). For now though I thought it would be good to be able to know when planning observations what comparison stars at least have XP spectra. I've therefore added red markers around sources that have Gaia XP spectra within a given radius from the target in the finding chart tools.
Code is probably not as good as it could be but it seems to run fine on my system. Let me know what you think

Alex

[StuartLittlefair]

This is a great idea Alex, but one that needs a little bit of work before merging I think.

Not every user is going to want to have these sources displayed on their images and, will also worry about what these circles are!

I think we need to add a catalog selector along the lines of the surveySelect dropdown box, and a LoadCatalog button.

Also, I don't think your sources will update their positions if you pan, zoom etc, so we need to implement something along the lines of the Ginga Catalog plugin (https://github.com/ejeschke/ginga/blob/main/ginga/rv/plugins/Catalogs.py)

[Alex-J-Brown]

While the Catalog plugin looks like it's probably the tool for the job, it seems like it might be a little beyond me at the moment to understand that documentation and implement it properly and with the filtering required (e.g. to just select sources with XP spectra rather than the full gaia catalog).

I agree that having the catalogs as a selectable option is a much better way of doing it though so I have implemented that now, adding a "load catalog" button with "none", "xp_sampled", and "xp_continuous" options. These options/buttons exist if astroquery is installed and plot the markers for sources with xp_spectra. From my testing they do update their positions when panning or zooming (in the same way as the target marker does, they're just added to the canvas in the same way) so it does seem to work at least

[StuartLittlefair]

I haven't forgotten about this, but I'd like to wait until I can integrate it nicely into a way of displaying catalog info more widely. Can you wait for that with this as your own fork @Alex-J-Brown ?

[Alex-J-Brown]

Yeah of course, I'm in no rush as I can use the current working version myself and others that want it can install from my branch. Perhaps I'll let vikcam know that the branch exists on my fork in case anyone else would be interested in using the prototype version