And Another, Since I Am Waiting for the Sun to Set

It takes a while for all the optics on a telescope to reach thermal equilibrium.  During this time, the image may improve or degrade, but the one guarantee is that the collision will change.  Collimate after everything's had cooled off.  Typically a half hour for a small reflector.  Hour or more for a big reflector of a Schmidt-Cassegrain of any size.