  The visual inspection of image and catalog data continues to be a valuable
aspect of astronomical data analysis. As the scale of astronomical image and
catalog data continues to grow, visualizing the data becomes increasingly
difficult. In this work, we introduce FitsMap, a simple, lightweight tool for
visualizing astronomical image and catalog data. FitsMap only requires a simple
web server and can scale to over gigapixel images with tens of millions of
sources. Further, the web-based visualizations can be viewed performantly on
mobile devices. FitsMap is implemented in Python and is open source
(https://github.com/ryanhausen/fitsmap).
