[[1ponders] (Paul)]

Here's a question for the guidescopers out there. Its one that's been nagging at the back of my mind (quiet Tony) for a while now. I maybe burnt at the stake for considering this heresy but here it is.

According to theory a guidescope should be at least the same focal length as the imaging scope, preferably 1.5x or longer. Now I understand the theory behind this. If your guidescope has a shorter FL than your imaging scope then your imaging scope may get trailing before you notice the movement in your guidescope, particularly if there is a large differences in FLs

That may well have been true when manually guiding using a reticle, but does the same hold true now when autoguiding using a webcam is so popular. I've noticed while using K3CCDTOOLS V2 that the guiding is done at a pixel level with the stars at almost their pin point level of focus (particularly when you drop the gain and brighness down), far more accurately than visually, no matter how high your magnification/long your focal length or accurate your reticle.

So given these considerations of smallness of target, responsiveness of guiding software and accuracy of the new breeds of motorized mounts is it still neccessary to have a guidescope FL equal or longer than the imaging FL. BTW I'm not considering camera focal length type lenghts (200-400mm) but short tube refractors of 450 - 600mm FL on, say, 2000mm imaging focal lengths.

Cheers