*
Saturday afternoon 23rd: 49F. 14.24 : Strangely complex surface detail. Image still soft.
Lots of heavier cloud has arrived!
It was very odd. Hours after the objective cleared of mist the D-ERF misted over on the inside. The hair drier and hours of dew band had not helped.
The three large thumbscrews make it difficult to wrap a band around the cell. Likewise with the objective cell. There is only the raised edge of the cell to which to apply apply heat.
I wrapped two heat bands in series on the main tube just behind the cells. This took hours to clear the internal dew. Probably because the counter-cell is a thick ring of turned plywood. Which would insulate the glass and metal cells. Even with regular blasts of hair drier all around the cell rims.
I don't have any aluminium large enough for a solid counter-cell. Perhaps I should be grateful because that would be a cold sink. Taking a long time to warm up after a cold night in the observatory.
Perhaps I ought to make a hinged door in the main tube. A little way behind the objective. Then I can blast the hair drier directly at the internal condensation. Without denying myself the ability to use heat bands on the main tube if the door was too close.
Or, I could make an aluminium sleeve to fit closely over the cells. To provide a direct path for heat conduction from the dew bands. An overlying layer of insulation over the heat bands might also help. I have already lost more than enough potential imaging hours to dewing.
*
No comments:
Post a Comment