To me...the real magic of Instructable contests is the incentive they give you to complete those projects that you've been kicking around for months. This is one of those projects for me. Unfortunately, I didn't get it done in time for the Space contest, but lucky for me, I think it will fit perfectly in some of the other contests that are currently running.
I live on a corner lot in a small town. That means to do even the most rudimentary astronomical observation entails a drive to escape the light which absolutely limits the amount of time one can spend stargazing. But not anymore...I built a mini light blocking observatory out of tarp and PVC...something I've been meaning to do for a long time.
Step 1: Materials and Tools
If you are using cheap blue tarp like I am...you're going to have to double them up to get adequate light blocking. The amount of pipe you'll need depends on the size of the tarps you use. I used 15 ten foot lengths of 1.25 inch schedule 40 PVC. I made a three panel mini observatory...but you could make more if you chose.
I used 7 (7'7"x5'7") tarps, 18 elbows, 13 Tees and 30 tarp bungees.
You'll need a saw for cutting PVC, and a drill, screws, 1/2 inch countersink bit and screw-driver or pvc cleaner and glue if you plan to permanently join your work.
Credit: The section on securement was inspired by the excellent Instructable "PVC 101" by trevormates. Absolutely worth reading even if you've constructed from PVC in the past...essential if you haven't. Link here.
Step 2: First Panel (back)
Lay out a tarp. Cut your uprights first. The leftover ends will make up your crossbars. Each panel has three uprights and two 2-piece crossbars. The uprights should be two inches longer than the height of the tarp top to bottom. I used all the same size tarps...so all my uprights were the same height. I had 9 total uprights for the panels and 4 that were slightly shorter for the door.
Start with the back panel. The width of the crossbars on the back should short enough that the tarp extends beyond the frame two inches on each end.
I used TWO full length leftover from the uprights connected with a T...then cut one end...so the center upright support on each frame was not quite centered. I did this to minimize waste. The important thing is to make sure the T is in the exact same spot top and bottom crossbar.
Step 3: Second Panel (side)
Make the second frame like the first...but this one is only going to be shorter than the tarp by two inches on ONE end (this will all make sense). On the top right corner...instead of an elbow...use a T connector.
Step 4: Third Panel (other Side)
Same as the second panel with the frame 2 inches shorter on one side. On this panel...put the T in the top left corner. .
Step 5: Assemble the Panels
Bungee the tarps to the center of the frames like they are in the first picture. Take the back panel (first panel) and side panels and zip tie the edges together (see pic 1 and 2). The T corners should both be on the top front...away from the zip ties.
Pull the rear edges of the side panel tarps around the zip tied uprights and bungee the corners around the top and bottom of the back panel frame on each side of the back panel (third and fourth picture). Now take the edges of the back panel tarp and overlap the side panel tarps around the corner and bungee them to the top and bottom of the side panel frame (Fifth picture). This will keep light from penetrating between the edges of the frames. Bungee the other end of the side panel tarps to the front uprights of their on frames. If there is a little gap...no sweat. We'll take care of that with the door.
Step 6: The Door Sides
I took a lot of pictures here so I could save you a slew of convoluted explanations. Hopefully they are self explanatory. The long sections are the same height as a tarp. We are going to use these to cover the small gaps at the front of the two side frames. Look through the next steps and you'll get the idea.
Step 7: Completing the Door
I didn't want to cut and sew a tarp...so this one is doubled over. You want it to be nice and tight...so thread it through the pieces you built in the previous step...then put pipe in the T's of one side, pull it taunt an make your cut marks. Cut and install.
Step 8: Hang the Door
Adjust the side panels in until the door fits over the outside off the panels and covers the gaps between the tarps and the frames. Measure, cut and install the top brace across the door hole.
Set the door in place. Rest the bottom on the toes of your shoes. Zip tie the top to the crossbar you just installed with 2 or three zip ties.
Step 9: Add Door Pole and You're Done With the Set Up!
Lift the bottom of the door pivoting it until it is parallel to the ground. Measure the height of the prop pole that goes into the T in the middle off the bottom of the door. Cut it and install it.
Step 10: Tear Down...
To tear it down...cut the zip ties that hold the door up and set it aside. Unbungees all the tarps that are connected to frames other than there own and fold them back, bungeeing them to their own frames. Cut the zip ties that hold the frames together at the corners and carefully lay them down.
Step 11: Secure (Optional)
The frames will hold together pretty well just pushed together...or you can glue them...but I like to screw pvc together. At the pipe-fitting junctions...using your 1/2 inch countersink bit, make your countersink, then drive a one inch drywall screw into the center of the countersink. For this project, one screw per junction is plenty.
Step 12: Store It Away or Leave It Up
I just leaned it up against the shed. It takes up very little space. I put it up and tore it down a few times and it takes about 10 minutes once you get the hang of it.
Hope you enjoyed this Instructable. As always questions, comments and
criticisms are always welcome. Clear skies and happy observing.
15 sticks of 1.25 inch PVC...$51
3 bags of tarp bungees........$12
Step 13: Addendum: Set Up in 12 Minutes
I set it up today for the first time since it was built, as Cleardarksky.com has a pretty good chart for tonight. Took a little more than 10 minutes to complete the set up. The sun is down but the moon is still up, so I haven't gotten the full effect yet, but all the street lights are blocked out, and I can hear cars going by within 100 feet...but their headlights are completely blocked. I'm calling this a successful test. Shot some video with my cell...uploading it now, so you can get an idea of the field of view. Hopefully, if all goes according to plan, after moonset I'll get some great stargazing time 20 feet from my door instead of 10 miles.
I uploaded some video, unfortunately for all of you, it is so dark that you cannot see the outline of the observatory frame (it is roughly an inch below the moon and parallel to the bottom of the video)...but for me, that is the whole point. What you are not seeing are the 6 streetlights, 9 security/porch lights, 5 illuminated windows and numerous vehicle headlights...just darkness and the moon. But, I uploaded the video, so I'll post it...prepare to be bored...
I will not be bored...I've got my red light, star map, binoculars and mosquito repellent....time to observe the stars!
UPDATE 8/12/16 - Everything worked perfectly...with one exception. As cars passed, the headlights would reflect off the shiny white top crossbar. To correct this, I think the frame needs to be scuffed with sandpaper and painted matte black. I'll update further when I get this done.