Project dimensions (approximate), excluding sunshield (a future project):
Height: 18” / 46 cm
Width: 17.5” / 44.5 cm
Depth: 27” / 68.5 cm
Scale calculations:
In real life, “Each of the 18 hexagonal-shaped mirror segments is 1.32 meters (4.3 feet) in diameter, flat to flat. (Webb’s secondary mirror is 0.74 meters in diameter.)” This makes the full 18-segment mirror 6.5m flat to flat. Source
My purchased acrylic mirrors are 85mm (8.5cm) flat to flat. Therefore, 132 cm / 8.5 cm = 1:15.53 scale.
Materials:
Gold acrylic hexagonal mirrors: amazon link example (or similar) ($15.99), each hexagon size 10 x 8.7 x 5 cm / 4 x 3.4 x 2 inches. This link also includes silver, which I used to practice with. You will need 18 gold for the primary, and 1 gold to make the secondary mirror out of. I ruined a couple during construction so I’m glad I ordered a second set. Back is adhesive.
You may wish to find another option that only includes gold,
(2) Formular 2×2 ft. project panels: Home Depot link example ($6.58/piece)
(4) “Readi-board” Black project foam board (2 for $1.00 at Dollar Tree stores, not online)- extra in case of mistakes
(1) Roll of Gorilla black duct tape “Tough and wide”: Home Depot link example ($14.97)- I got the wider kind to cover more area easily.
(3) Fiberglass driveway markers: Home Depot link example ($2.28 / piece)
Tools needed:
Sharp blade to cut foam board (or anything that can cut through the thicker project foam board panel cleanly- I didn’t use a serrated knife because I was concerned about not getting a clean cut)
X-acto of hobby utility knife (optional)
Black permanent marker (if the thin “readi-board” you purchase has a white inside- if you can find one that has a black foam inside, that would be easier)
Ruler
Steps:
I figured this out as I went, so these instructions aren’t very detailedand do not include specific measurements
For reference guides, I used the “WebbAR” app for iPhone, NASA’s Eyes on the Solar System (web), JWST User Documentation Homepage, this NASA JWST link and online photos.
Primary mirror assembly:
Note: Using my silver acrylic mirrors, I first tested if I could create a concave shape like the actual JWST but this proved to be too complicated so I resorted to mounting them on a flat surface only.
I started by peeling the adhesive backing off the 18 hexagonal mirror segments and affixing to the project foam board in the JWST pattern, and then cut around the outside perimeter with my x-acto knife, flush to the mirror edges. Everything else is approximately to scale depending on the completed primary mirror size using the specific acrylic mirrors you purchase.
Using your black permanent marker, color in the white sides of the foam board
Next, I used a 2’x2′ project panel and overlaid the primary mirror assembly, and drew cutting lines around the primary according to the actual JWST. I guess you could call this the “backplane.” I then cut it out, and last step painted it matte black. I will glue the primary mirror assembly to this thick board later.
I then created the protruding “Aft Optic Subsystem” that goes in the middle of the primary mirror assembly. I made this out of the thinner foam board out of 4 pieces for the sides, and 1 for the front (which I carved the approximate openings through which light travels into the instruments)
Secondary mirror assembly:
Webb’s secondary mirror is 0.74 meters in diameter (source), and using 1:15.53 scale, my model size will need to be a circle 47mm in diameter.
I first used a compass to draw a circle 47mm in diameter on a piece of paper, then cut it out to serve as my template. I then traced the outline onto a mirror segment with a fine tip marker. Acrylic is not easy to cut without splintering, so I cut about 2cm further outside the line with heavy duty scissors, and then used a Dremel tool with a sanding attachment to carefully decrease the size until I got to the line I marked. This took 2 attempts before I got it correct.
Then I needed to carve out the housing for the secondary mirror which also joins the “tripod” arms securely. See photos for the shape I carved out, with 3 angled holes drilled.
I cut 3 pieces of the fiberglass driveway markers each to 19 inches, and inserted into the secondary mirror assembly.
After this was all done, I covered everything with black duct tape as shown.
Joining Secondary mirror to main telescope assembly
I cut out small areas in the corners shown on the primary’s “backplane”, and used duct tape to affix the tripod to the primary assembly. I made the holes smaller than the width of the tripod arms so it was a tight fit.
Constructing the Integrated Science Instrument Model (ISIM)
I used a combination of the thicker foam board to make the 5 core sections needed for this module (2 sides, back, top, bottom), and then used thinner foam board for the decorative elements to match the real JWST, but the bottom is angled to allow this to be a table top model. All covered with duct tape, and simply taped to the back of the primary mirror “backplane” to keep it all together.
Copyright 2022 Marty McGuire