01A sky that is actually computed
9,096 stars from the Yale Bright Star Catalogue in a 53 KB binary, projected for the site's real latitude and longitude at the visitor's own clock, scrubbable through the night by pointer or keyboard. The positions come from Meeus and are verified against an independent implementation to 0.01°.
02Availability the moon decides
An eighteen-month calendar of moonless astronomical dark — sun below −18° and moon below the horizon at once — sampled every five minutes across 547 nights. Deep-sky sessions are genuinely unbookable about twenty nights a month, and each closed night says why.
03Three finished themes, one of them red
Day, night and a hue-locked red night mode that mirrors how observatories preserve dark adaptation, with its own duotone photography so no white appears anywhere. Auto follows the observatory's clock rather than the visitor's.