Off axis guiding with DSLR

[Moon]

Has anyone tried something like this product with a DSLR and guide camera?

http://www.teleskop-express.de/shop/product_info.php?info=p1188_Off-Axis-Guider---nur-9mm-Baulaenge---Direktanschluss---Canon-EOS.html

How hard it is to find suitable guidestars?

[Merlin66]

I've got and use, the Lumicon 2" version and the Celestron Radial Guider OAG, they are both good at their job. The Celestron is a bit better as it allows about 110 degree of rotation of the pick-off prism without any movement of the camera.
Depending on the guide method; crosswire eyepiece/manual or CCD it's sometimes a bit awkward to find a suitable bright star to guide on ( lots of faint stars!!)
I use a QHY5 for guiding. BTW you'll probably need a 25 or 50mm extension tube on the guide port; depends on the back focus to the CCD chip.