The Virtual Astronomy Multimedia Project defined the AVM standard to tag astronomical images (jpeg and tiff) with useful meta data. The meta data is embedded in the image file itself a bit like a FITS header. To tag an image you need software such as Photoshop or Adobe Bridge.
image1 in this case:
<img src="antennae.jpg" id="image1" />
The example above plots all available AVM tags but you can select specific tags as you prefer e.g.
obj.tags['Spatial.Equinox']. Here are the possible AVM keys: