- iObserve - OS X app for observing planning
- JSkyCalc - calculates everything you’ll need for observing, and it knows all major observatories. graphical revival of the venerable Skycalc. blog post
- staralt
- AstroAirmass Dashboard Widget
- ESO Sky Calendar Tool - Sunrise, Sunset, twilights, and moon rise/set times for a month (based on SkyCalc)
- Object Observability over long periods (based on SkyCalc)
- Airmass Calculator (based on SkyCalc)
- ESO Airmass Plotter
- Keck Airmass Plotter - specific to Keck, but really excellent on-the-fly plotting (Java based)
- skycalc and skycalendar can be installed on your own computer.
- Python GUI to skycalc
- astropysics.obstools.Site.nightPlot