Easy to make light and wind screen

Most of us are having to contend with worsening light pollution at our homes or other observing sites, and not just the overall sky glow, but nearby lights. Since LEDs became cheap and widely available, people just have to have more and more lighting. Many still think it deters crime (it doesn't), so they add lights, always brighter and rarely properly shielded. I can count at least nine lights, sometimes more, that are consistently in my eyes in my front yard, where I have to observe (trees in back). I also have cars stopped at a nearby traffic light whose headlights point directly at me.

But you can fight back, as I noted in my article on building a "Redneck Observatory," with stuff you have around your house or garage, if you have one. One of the items I used was an old PVC pipe target stand I used to use for .22 target practice out at an unsupervised public range. I added a wood frame and a blanket. I'll use that light screen more often than setting frames up against my garbage cans because I observe more now on a grassy strip on my front lawn and it's sometimes messy to roll the cans across the grass. I decided to make a second one to block out the lights across the street and the headlights and lights 90 degrees around from there.

Some people say they do fine just using a hood over their head, and I do use a hoodie to reduce light trespass into my eye and eyepiece, but I find it's just not very satisfying to see all those lights glaring at me as soon as I raise the hood. I also don't like being lit up like daylight and unaware of what's around me. If that works for you, though, no need to bother with a screen. But I think there is a primodial desire for shelter from outside intrusions that makes the screens, or an observatory, much more satisfying. It's kind of like a snow fort for amateur astronomers!

Light screen

The light screen consists of a base of 1-1/2" PVC pipe in two upside down "T" configurations that holds a taller frame of 1x2 or 2x2 furring strips (or fancier wood if the spirit and wallet moves you; that's a piece of old baseboard molding in the picture). Over that you drape a cheap moving blanket and use plastic spring clamps to hold it to the frame. The height depends on where the lights are in relation to your eyepiece height and how much room you want to maneuver. This one stands 72" tall to block out lights from right across the street. Do some measurements at night to be sure you end up with what you need.

Why the moving blanket? You could use a tarp, but I'm in a residential neighborhood and poly tarps tend to be noisy with any kind of wind. Moving blankets are cheap, they block out all the light, they are relatively heavyweight so they don't flap aound much, and when they do, they are quiet. You can also use them as blankets when observing from a recliner or to pack around your telescope.

Schedule 40 PVC pipe is generally sold in the United States in 10' lengths. My car can only fit an 8' length, so I used the self-cutting molding station in the store to cut off two feet of it. You could also bring a hacksaw and cut it in the parking lot, but then you'd be spreading plastic sawdust all over. Pine furring strips or their equivalent are usually 8', so no problem there. 

You'll use four PVC "T" fittings to make the joints. These are friction fit together so you can take it apart as needed.

The process, in a nutshell, is to cut the PVC pipe, assemble it, cut the furring strips, and assemble the frame. The frame just sits in the pipe openings.

Wind screen

The light screen can do double duty as a wind screen if you substitute 2x2s for the 1x2s and stake the feet into the ground or weight them down with something, which would be necessary if you set up on pavement. The  blanket shown is a small 72x40" (actual 70x39").

Depending on whether you sit or stand, and how tall your setup is, you may also want to lower the height, as shown at left.

You can adjust the width of the PVC feet by cutting different lengths for the cross piece. 

Note that  you'll want the side facing us in the image at left to be on the windward side so the blanket is blown against the frame. You can use additional spring clips to hold the lower part of the blanket to the frame if necessary.

Be realistic about how strong a wind it will be able to handle, and build accordingly.

Staking down the four feet will help keep the screen in place with some wind. I wouldn't set it up in wind over about 15 mph so you don't risk it plowing over your telescope if it lets go. You be the judge. (Put the stakes all the way in. I didn't bother for this picture but it'll keep it anchored better.)

If you're on pavement, use weights instead, but they have to be more than about 10 lbs. per side to hold it in any kind of wind. Leaving space below the blanket at the bottom will help it from becoming a sail. You want the protection at the level of the scope tube.

Parts list

• One 10" long 1-1/2" (inner diameter, it's marked on the pipe) Schedule 40 PVC pipe.
• Four PVC 1-1/2" Ts (S-S-S) for pressure applications. Make sure all three openings are 1-1/2" and smooth inside, not threaded. Don't get cleanout Ts, the pipe won't go in straight in the middle connection. The cleanout Ts to avoid have a slight curve to the outer contour.
• Three 8" long 1x2" furring strips (or 2x2" if  you want it to be sturdier to stand up to higher wind, at the expense of a bit heavier frame). Seems that the big box hardware store selection gets worse every year. Cull through the boards to find the least warped, twisted, split, and otherwise pathetic specimens you can find. Find a good lumber yard instead if you can. You can use treated or untreated wood. Treated will be more expensive and heavier. Unless you are leaving the screen out in the elements (not recommended) you really don't need treated.
• Eight wood screws. Make sure they are long enough to join the two pieces of wood together firmly without protruding out the back side. 1-1/4" should work for 1x2s (which are really 3/4x3/4) and 1x2s to 2x2s (which are anywhere from 1-1/4" to 1-1/2", pressure-treated being somewhat smaller), as long as you put them through the 1x2 first.
• Alternative to wood screws: Four 1/4-20 knobs and four 1/4-20 T-nuts (less than 3/4" long). This allows you to disassemble the frame for transportation.
• Cheap moving blanket or other blanket. A smaller size, like this 70x39" blanket (actual measurement) won't cover the entire frame from top to ground, but you probably don't need to, and it's lighter and less bulky than a larger blanket. Really, any blanket or tarp will work, depending on what you want. You can size the frame to fit whatever blanket works for you.
• Four steel nail-type stakes (such as these) or weights (bags of grass seed or soil work well on pavement).
• Four to six plastic spring clamps for holding the blanket to the frame.
  
  

Tools

• Wood saw of some kind
• Hacksaw or wood saw to cut the PVC pipe (unless you have a suitable pipecutter for 1-1/2" pipe).
• Electric drill, with a countersink bit that matches your wood screw size (size 6 or 8 should work) and an 11/16" bit for drilling the PVC pipe to accept typical steel nail peg stakes
• Phillips screwdriver
• Sandpaper
• Paint if you want to paint the wood

Build it

You can adjust any measurement as you see fit, especially if you plan on transporting it in your car, but these are my suggested dimensions.

Cut the following pieces of PVC pipe:

• (4 pieces) 16" each (these are the feet)
• (2 pieces) 9" each (these are the lower uprights)
• (2 pieces) 4" each (these are the upper uprights)
• (1 piece) 24 to 30" as you desire (this is the crosspiece and will determine the width of the frame uprights). The frame in the images at the beginning of the article has a 24" PVC crosspiece, for reference.

If you want the widest possible spread between uprights and you have to cut the pipe to fit it in your car on the way home from the store, cut a 30" piece off the 10' length in the store.  You can always shorten it, but that will allow  you to cut all the other pieces to the dimensions above for a total of 120". After each cut, use a small piece of sandpaper to clean the cut edges. Sweep or vacuum up all the plastic dust and bits. Wear a mask so you don't get plastic particles in your lungs.

Brace each foot piece in a vise, clamps, or wood, and carefully drill a hole just big enough for the stakes you are using through both walls of each end, about 3 inches from the ends. The stakes will go through these holes into the ground, if you use them.

Assemble the pipe frame as shown in the image at right.

Now, decide how high you need the wood uprights to be. You will be putting the wood uprights into the open pipe holes. I cut two 8" pieces of 1x2 and slip them into the pipes first. This allows the uprights to be shorter and still give me the height I want.

Left: An 8" piece of 1x2 dropped into the upright pipe from above will compensate for making the wood upright 8" shorter and easier to transport.

Cut the wood uprights from 1x2s (or 2x2s for a heavier frame). Cut a wood crosspiece to span across the two uprights as a brace. Cut a crosspiece for the top of the wood frame, over which you will drape or attach the blanket. This will probably be wider than the pipe base because you want good coverage with the narrowest base that will be stable. I used leftover wide baseboard molding for my top crosspieces, but you can use a piece of 1x2. 

If you use 2x2s for the uprights you will probably have to shave the four corner edges down some on the lower 8" of the upright so they'll fit snugly into the pipes. The 1x2s should fit without modification.

Left: I had to shave the ends of the 2x2 uprights down with an orbital sander so they would fit into the pipes. 

If you're making this more wind resistant, use 2x2s instead of the 1x2s for the uprights, but you can probably stick with 1x2s for the crosspieces. The lighter the frame is, the easier it is to set up, and the more likely you are to use it. The heavier it is, the more wind resistant. It's a tradeoff.

You can fasten the wood frame together with wood screws, two at each joint. However, to make it portable so you can take it to a darker site that maybe has an annoying light or two or is often windy, you can instead drill holes where the pieces connect, then insert knobs through the two pieces and fasten them with nuts or wingnuts. 1/4-20 threads should be fine.

Left: Using knobs instead of wood screws to attached the frame crosspiece. I have the pieces labeled with painter's tape so I can reassemble it easily. The hole in the side of the upright was a mistake. It's easy for a bumbling woodworker like me to not to get the hole straight, so I had to redo it on the other face of the 2x2. 

Right: Close up of the knob attachment point. Use a flat washer on both sides, and a nut or wingnut on the back side. These are all 1/4-20 size threads.

Here is the finished frame for the transportable wind screen. You can drill additional sets of holes in the uprights for a variety of heights.

To pack the screen in a car, you detach the center cross pipe in the base and the crosspiece or pieces of the wood frame. Consider the length of the uprights in this case so they fit comfortably in your car (maybe with ends in the passenger seat footwell, extending through the gap between front seats, and across the tops of the back seats). This is why I like the 8" pieces of wood inserted into the pipes first. That allows you to use shorter uprights.

Once you have everything cut, sand the wood so you don't get splinters and paint it if desired, mostly to smooth the surface further and protect it from dew and other moisture. Bare wood and the white PVC pipe will show up well at night, but if you use it as a wind screen in a really dark sky, you might want to sew or tape some white fabric or tape to parts of the blanket so no one walks into it in the dark. If you have a site that dark, I envy you!

Why not make the whole screen frame with PVC pipe? I used to have one I designed that used 3/4" pipe, shown at left, and it worked well for a while, but after some years the pipes were either too loose or too tight and setting it up and taking it down became a chore. My wife sewed the fabric with pockets to slip the pipes into and velcro tabs. The wind would often pop it apart and eventually broke a couple of pieces. So I recommend a hybrid PVC and wood frame. It's also lighter and cheaper. PVC pipe has gone up a lot in price.