The most important accessory for a Schmidt-Cassegrain telescope — or anything else with glass at the front of a telescope tube, for that matter, including Maksutovs and refractors — is something to prevent dew from accumulating on the glass. There’s nothing more annoying than having your telescope fog up shortly after you start observing. Among the preventative measures are a dew shield, which reduces the glass’s exposure to the outside air, and a dew heater.
The material in question is a Neoprene back wrap. It came with a hot and cold gel pack, of which, thanks to my little disease, I have several. It has Velcro, so all we had to do was wrap it around the telescope and voilà! Instant dew shield. Serviceable, if a little floppy and funny-looking.