I have to store my 12" Newt in the shed and I keep getting these really annoying spiders spinning webs inside the OTA. I hadn't used the Newt for a while and looked inside the OTA for the first time last night as it was dark and clear and shock horror full of spider webs! And spiders! I tried to vacuum them all out and got the spiders but the webs were everywhere including the primary! I had to take it out and rinse it in distilled water to get them all off.
Simple solution, I went on eBay and bought a padded surfboard bag with a zip and a carry handle for around $30. No more spiders. Just a thought if you have the same problem.