by Jay Reynolds Freeman
The essence of painting seems to be cleanliness in general and surface preparation in particular. Paranoia about such matters formed the basis for my operations.
I was happy with the black finish on the NexStar 8 tube ends, but I wanted to repaint the gray part. I chose not to disassemble the OTA; I worked with optics installed. I taped the dust covers on and masked the black parts. Then I permanently sealed the cracks between tube wall and end fittings with red glazier's putty -- often used for auto body work. With a wet fingertip and a wooden shish-kebab skewer, I forced a tiny bead of putty into the cracks.
After it dried, I roughened the gray with 150 grit sandpaper, so new paint would stick. Sanding also got rid of smears of glazier's putty. I wiped the surface with a tack cloth, checked the masking, and sprayed on several coats of white primer -- Orchard Supply Hardware's house brand. I supported the tube horizontally with wooden v-blocks at the ends, and worked a section at a time, rotating the tube as I progressed.
I also painted an old tin can, for experiments. I put it in a warm part of my house, stashed the tube in the garage, and left them alone for a week, to dry.
The choice of white primer was made carefully. Paints are often somewhat transparent: Primer color affects appearance, even after many finish coats. I once sprayed horizontal stripes of several colors of primer on a test piece of cardboard, then overlaid them with vertical stripes of several finish colors, using two or three coats. Primer color made a noticeable difference in results. White primer made the light-colored finishes brighter and more intense.
I have trouble painting strongly curved surfaces, like telescope tubes, from spray cans. Enough paint for a smooth finish runs or sags on the slopes, so I use many light coats, which tend to give a matte surface, even with gloss enamel. This time, I wanted something shinier. So I used another hardware-store commodity, "No. 7" brand of white polishing compound. An hour with it and a wet rag got the primed surfaces acceptably smooth. The compound cleans up with water.
The color coat was a different kind of spray paint, that dried much more quickly than the primer. The recommended application was several light coats, a few minutes apart. That worked on my witness sample, but for the larger OTA, I painted more or less continuously for fifteen or twenty minutes, rotating the tube as before. By the time I worked around the tube, where I began was dry enough to recoat. After putting on four or five layers, I again set everything aside to dry thoroughly.
The weather was hot, so in a few days, I could spray on AerVoe clear acrylic, to improve gloss and protect the color. It went on like the color, and also dried quickly. On inspection, I found a place where I had not smoothed down the primer sufficiently, and had to repolish and touch up that area. After more time for drying, I very lightly applied white polishing compound, removed masking tape, and neatened the edge of the black with a magic marker, and also by using a hypodermic syringe to flow black ink into the crack where the black OTA end fittings mated to the orange OTA main tube. Then I waxed the paint with a liquid car wax, "Nu Wax", and was done!
You who have seen my pink and gold modified Brandon 94, or my goth-hued 10-inch truss-tube Dobson, or Refractor Red, will wonder what color the poor NexStar 8 is now. I gave a clue earlier. Out of respect for the classic Celestron 8, what used to be metallic gray is now red-orange -- fluorescent red-orange, one of Rustoleum's specialty paints. And it's bright! So when bunny-suited bureaucrats from atomic regulatory agencies show up, checking out reported violations of the nuclear test-ban treaty, tell them it's just me. And you'll need shades and sunblock when my NexStar 8 attends a star party.
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