Bennett catalogue of deep sky objects
Jack Bennett, a comet hunter, made a catalogue similar to Messier's for the southern sky.
Cloudy Nights thread on the development of plate solving
Some nice history of the development of astronomical image plate solving, finding where in the sky an image is located, especially from the amateur perspective.
Cloudy Nights: which non-linear image stretch to use on astrophotos?
On PixInsight, it seems that GeneralizedHyperbolicStretch and MultiscaleAdaptiveStretch are the state of the art, with the HistogramTransformation that I've used before being the old way of doing things.
PixInsight GeneralizedHyperbolicStretch
A 3rd party PixInsight plugin that "implements pixel intensity transformations defined by generalized hyperbolic (and other) equations."
Stargazing buddy
A practical guide to observing the night sky for real skies and real equipment
They describe it as a modern field guide.
OnStep
GPL-licensed firmware for controlling telescope mounts.