Akkana's Homebuilt 8" Dob -- Shroud

[8 dob with shroud] [close-up of shroud top fastening] I have mixed feelings about shrouds. They can hurt cooling and cause tube currents: one of the advantages of open-tube scopes is that the mirror is so much more open to the air, allowing it to cool more quickly and preventing currents of air which circulate within the tube, often running right past the focuser where turbulence hurts the image the most. They can also catch the wind and make a dob less stable on windy nights.

On the other hand, in bright conditions, a shround can keep ambient light from getting into the light path, can keep passers-by from shining flashlights on the mirror (or, worse, dropping something on the mirror or touching it out of curiosity, common occurrences at star parties where there are lots of small children), can keep some dust off the mirror in dusty conditions, and can keep the mirror from dewing up in extremely wet conditions.

So I wanted a shroud, but I wanted it to be easy to put on even after the telescope was fully assembled; a shroud that was tight around the tubes and didn't fit over the top cage wouldn't work.

The first step was to get my aged sewing machine reconditioned and re-learn how to use it, a bit of an ordeal, but after a month or so of waiting for the repair place, I was ready to sew. All that remained was to set the 'scope up in the living room and use it as a fashion model, pinning cloth on it and trying out different designs.

I used "Riptide" nylon, which is extremely light and adequately opaque. It has a shiny side and a matte side; of course, the matte side goes on the inside.

The shroud snaps together with six pearly-white snaps, and has a drawcord at the top to hold it on the top cage. It fits fairly snugly around the tubes.

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8" dob top cage
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