guiding through Off-Axis Guider

Hi,

Does anyone guiding through off-axis guider or is is it better off using for example Orion ShortTube 80? I'm talking about using the Orion StarShoot AutoGuider...
Cons and pros, please.

The rule is that off axis guiders are preferred when you have mirrors, and separate guidescopes are acceptable for fixed lens systems.

The problem with mirrors (either Newts or especially SCT's) is that the mirrors can slightly shift positions in their holders. This means that they are no longer pointing to exactly where the guidescope is pointed. If this happens while guiding, you have funny looking stars!!!!

You can have this problem with a refrator/guidescope combination when the mountings do not hold the respective scopes rigidly. It is called flexure. But with good mountings, it is not common. (You can also get flexure from inadequate focusers/drawtubes, heavy cameras, loose mounting screws, and whatever gremlins inhabit a system---Off axis guiding overcomes all types of flexure problems.)

In practice, with modern shorter exposures and very good mounting of the guide scope, the separate guidescope route is much easier to pull off. It also gets you a much wider selection of guidestars.

And many dedicated astro cameras have guide chips in the same head as the imaging chips, thus making the choice between Off axis guiding and separate guidescope unnecessary.

Alex