Computing Exposure Times with the IRAF Task CCDTIME [2]

ISPI Exposure Time Calculator [3]: for ISPI infrared imager on Blanco 4-m telescope.

SMARTS Imager Exposure Calculator [4]: for 0.9-m CCD and 1.0-m Y4KCam

Object Visibility [5]: ING utility which plots altitude against time for a particular night (Staralt), plots the path of your objects across the sky for a particular night (Startrack), plots how altitude changes over a year (Starobs), or gets a table with the best observing date for each object (Starmult).

Worldwide Astronomical Resources [6]