Grant,
You may be thinking of a short piece I wrote in the May 2009 Astronomy Now, about Dave Tyler’s C14 dessicant arrangement? Dave made such a tube to slide into the focuser of his Classic C14. The tube was 64cm long and 5cm diameter, with the end drilled with 200 8mm holes. Silica Gel bags were stuffed into the end and a cap used so that the bags could not fall out. At the focuser end the tube was more than 50mm across to prevent it falling inside the SCT. I attach Dave Tyler’s photo of his system. Unfortunately this would NOT work with an EdgeHD design due to the corrector lens inside the drawtube.
Martin
