Intro: Starwheel for Backyard Astronomy (Planisphere)
Learning to find your way around the night sky can be a daunting task when first faced with a sky full of stars. Once you do know the sky, orienting yourself every time you look up is not easy because the sky is always changing. In both instances, a good map goes a long way to making your time under the stars a more enjoyable experience.
Like ordinary maps of the Earth, there are many different kinds of star charts available, but one of the most useful for the purposes described above is a planisphere (also commonly called a "starwheel"). This is a chart of the sky that can be set to any night of the year at any time of night and shows you a basic map of the constellations.
This Instructable will help you construct a basic planisphere to learn and enjoy the night sky.
Step 1: Materials
For this project you will need the following materials:
- File folder
- 2 Sheets of cardstock (or a second file folder)
- Double sided tape
- Printouts of planisphere pieces (PDFs, included in the next step)
Step 2: PDF Patterns
These are PDF patterns for the pieces of the planisphere, for US Letter size paper. Print them full size. They are provided with minor color enhancements, but printing them in black and white should work just fine. At night under a red light, the color will not be noticeable.
The patterns are:
- sleeve.pdf: this is the outer shell, that you use to set the time. The "viewer window" in this piece shows the sky map.
- constellationsChart.pdf: this is the basic starwheel map, showing the major constellations and their names
- brightStarsChart.pdf: this shows all the major constellations, with the names of some of the brighter stars labeled. Only a few of the constellation names have been marked, to keep this chart from being too cluttered.
- binocularChart.pdf: this shows a few of the best "deep sky objects" (nebulae, star clusters, and galaxies) that can be seen even with small birding binoculars. To keep this chart from being too cluttered, only a few of the constellations have their names marked
- binocularGuide.pdf: this is very basic information about each of the binocular target
Step 3: Planisphere Sleeve
(1) Cut out the "planisphere sleeve" pattern, and lay it on the file folder. The left edge of the pattern (between the "East" and "South" arrows) should be placed long the folded edge of the file folder -- the fold will be one edge of your planisphere.
(2) Trace around the outline of the pattern, then cut it out of the file folder. Make your cut through both sides of the file folder, so it opens like a book.
(3) Tape the pattern to the front of your file folder cutout. I use double-sided tape in all steps of this Instructable because it doesn't warp and wrinkle laser-printer paper the way glue does.
(4) Using a hobby knife, cut out the white oval in the center of the sleeve, cutting through both the paper and the top layer of the file folder. Use a cutting mat or a piece of scrap cardboard slipped between the file folder layers to make sure you only go through the top layer.
You should now have an open oval; this is the window you will view your starmap through.
Step 4: Starwheels (Map Inserts)
Cut out the various starwheel charts. These are the maps you will use in your planisphere sleeve. They are designed to be interchangeable, with different maps for different purposes. You may also want to make a few extras, if you like to annotate them on your own as you learn the sky.
The planisphere sleeve is designed to work from one side only. You can make your starwheel maps single sided, or make them double-sided and flip them over according to what you need at any given time. I make them double-sided, so I don't have to carry too many with me.
My two-sided combinations are: Constellations (side 1) with Bright Stars (side 2); Binocular Targets (side 1) with Binocular Guide (side 2).
(1) For each starwheel you want to have, trace a circle on a piece of cardstock, and cut it out.
(2) Tape the starwheel patterns to the matching cardstock circles. Make sure you have tape all the way to the edges, to prevent the paper from lifting up as you use the starwheel. The orientation of the pattern on the cardstock doesn't matter, only that it gets centered on the cardstock.
Step 5: Stapling the Sleeve Together
(1) Staple the planisphere sleeve on the hash mark near the "East" arrow, and on the hash mark just over the word "planisphere." These are containment staples that keep the starwheel centered on the viewing window.
(2) Slip the starwheel in the sleeve, resting it against the original fold of the file folder, and near the two staples you just put in the sleeve.
(3) The placement of the last staple will be in the vicinity of the hash mark near the "West" arrow. Depending on how well you cut your circles, how centered your pattern is on the fold of the file folder, and how easily it turns between the layers of the sleeve, you'll want to adjust the exact placement of the last staple. Your goal is for the starwheel to turn easily, but not fall out!
(4) Once the last staple is placed, insert any starwheel between the sides of your planisphere sleeve. It should turn easily, showing different constellations through the oval window. You're done!
Step 6: Setting Your Planisphere
A planisphere shows a simple map of the sky at any time of any night of the year. To set the planisphere, turn the wheel inside the sleeve until the current date matches the current time. The stars that show through the oval window should now be the stars overhead.
Stand facing south. Hold the planisphere over your head and turn it to the side marked "NORTH" is pointing behind you. The label "SOUTH" should be pointing in front of you, "EAST" should point to your left, and "WEST" should point to your right.
Step 7: Using Your Planisphere
The stars showing on the planisphere should be the same stars you can see above you. The edges of the open oval are the horizons, and the center of the oval should be over your head (the "zenith").
To use the planisphere to see the stars in a given direction, start facing south with the planisphere overhead, as described in the last step. Grip the horizon in the direction you want to look, and pull that side of the planisphere down, as if you were trying to match the edge of the oval to the horizon.
Doing this, the planisphere should be vertical, but turned on one of its sides, and shown in the example figures above. It feels awkward at first, but with practice you'll get the hang of it!
Be aware that near the edges of the oval, the shape of the constellations are distorted. This is a consequence of squishing the whole sphere of the sky overhead onto a small, flat oval. With some practice, you will be able to recognize the distorted figures.
It is not always convenient to stand with the planisphere directly over your head. You can follow the same orientation procedure described above, but laying down on the ground. If you would like to face a different direction, simply hold the planisphere so the appropriate direction along the oval is matched to the horizon you are facing. For instance, if I'd like to look east to see what stars are rising, I hold the planisphere so the side of the oval labeled "EAST" is against my eastern horizon.
Good look, and happy stargazing!
PS: If you need a redlight to use your planisphere, I've written an Instructable for that too!