With so much clouds around these days/months, I came accross this FREE software which is suppose to emulate a guide star on your computer screen with sidereal movements/tracking allowing you to test your autoguiding, periodic error, etc indoors. It appears all you need to do is setup a laptop with this software around 5 meters away, focus onto it and start testing your autoguiding or recording your mount's periodic error, have downloaded but not tried as yet. Just thought it may be of interest to the group.
http://sweiller.free.fr/SGE/SGE-star...r.htm#download
Cheers
Eddie