FLOCKING (Cold weather use and reduction of internal reflections)

It's the little things that can make or break winter viewing when the temps start to drop. Mirror stability is a big one, as temperature changes can affect both the size and shape of the glass. Doesn't take much of a difference to throw off your collimation or alignment. Zhumell provides heaters to help, but you do need to set up at least an hour in advance for those to do what needs doing. The metal barrel soaks up cold though, and those heaters end up working extra hard to keep the primary mirror at a good working temp.

Common solution is to "flock" the barrel, which consists of adding an insulated liner to minimize heat loss. First step is to strip all the optics ... here I've done just that, as well as added foam bumpers to space the flocking material from the barrel. The flocking I used has a stiff plastic liner, so it spaces out nicely and traps air for improved R-Value. The metal strip you see on the top of the barrel was added for the inclination guage which will be covered later. The metal strips on either side are for the transport handles, also covered later.

NOTE: The flocking material also does double duty in reducing reflections inside the tube. Manufacturers do apply a dull coat surface inside, but that tends to degrade quite fast and certainly doesn't supply the light absorbing characteristics of a woven matte surface. Simple cloth flocking can be glued directly to the metal surface, but you'd better have it right the first time! I used the ProtoStar backed flocking material, without adhesive.


Simply a matter of cutting the material to size, rolling it smaller than the barrel and sliding it in. Once it's more or less in place, let it "rest" for a bit and expand evenly around the barrel. I did end up pulling it out and adding a couple extra strips of foam right at the seam line as it wanted to deform there. I also added a strip of carpet tape to hold it in place and keep it flat while it settled in. DO make sure any mounting hardware is already installed before setting the flocking in place!

Here you can see the barrel with the flocking installed. The seam is to the left, and you can see where two pieces are joined towards the base. That's the secondary mirror at the top.

One other detail - the objective is to eliminate any reflective surfaces in the light path. This also required forming a piece of the flocking to cover the focuser assembly ...

The focuser slides back and forth inside this piece. You'll want to make sure this does not intrude into the light path at any time. That's simply glued and taped, then pressure fit into the hole in the barrel flocking. I also added a rubber ring at the top to dress it up a bit and seal the end. This was pulled out of the scrap bin, left over from an old motorcycle fairing. As you can see, I also upgraded the hardware on the secondary mirror. One less tool to have to find when collimating the scope.

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