Large Image Safe Solar Viewer/Eclipse Viewer

Large Image Safe Solar Viewer (LISSV) - 2 lenses

Acknowledgements:

• TR Richardson deserves so much credit for his page on safe solar viewers.  Without his extensive write-up I never would have been able to make this work.
• https://richardsont.people.cofc.edu/safe_solar_folder/index.html

Introduction:

• In 2017, I observed my first solar eclipse using a pinhole camera.  While this worked, it was mostly unsatisfying because the projected image was very dim and small.  
• Fast-forward to 2023.  I realized that with two eclipses hitting Texas in a short period of time, I needed to up my game.  Thanks to TR Richardson's page, I was able to understand what was needed to make my own version using 3d printed mounts for the lenses and screen.  
• I looked around my house and found a fiberglass painters pole which would be easy to mount the lenses on since it is round.  To keep the viewer pointed, I found a tripod with a large ball head mount.

Notes:

• Because there is such a dizzying array of lenses and fiberglass poles, you will need to be able to modify the fusion 360 file I have provided to adjust the models to your needs. 
• I have tried to make all the mount and lens sizes easily changeable from the user parameters (modify>>change parameters)
• NO PLA if possible.  I highly recommend using ABS, ASA, or PETG.  The main objective lens is basically a magnifying glass and has the potential to easily soften PLA.
  • I printed my mounts in ABS.  If you are using a different material you may need to experiment with sizing as ABS shrinks about 0.6% after printing.  

Fusion 360 Parameters:

• ObjectiveDiameter - The diameter of your main objective lens.
• ObjectiveThickness - Thickness of the very edge of your main lens.  The main objective mount has a slot to help keep the lens straight.
• BarlowDiameter - Diameter of the smaller, barlow lens.
• PoleDiameter - Diameter of the main part of the pole (ie the yellow part) you will be mounting the lenses on.
  • This adjusts the size of the hole where the lenses mount to the pole.
• 2ndPoleDiameter - Only adjusts the image of the silver part of the pole.  Does not adjust any of the mounts.
• MaxImageDiameter - Max projected image size that you expect to get from your solar projector.
  • The default size is 220mm which is around 8.6".  If you have a monster lens and want to project a bigger image, then the mounts will need to be further away from the pole.  
• m3HeatsetHoleSize - Size of the hole for the m3 heatsets.  Take the diameter of your brass heatsets and subtract 0.3 or 0.4 from it.  
  • Alternatively, if you don't have m3 heatsets, you can set it to 2.7mm or 2.8mm and screw straight into plastic.  It's not the best long-term, but it works!
• TripodHeatsetHoleSize - size of the hole for the heatset that mounts into the tripod.  Measure the diameter of your heatset and subtract 0.3 or 0.4mm from it.
  • Alternatively, you can try just screwing straight into plastic by subtracting 0.2mm or 0.3mm from your bolt size.  I'm not sure how well it will work since this hole supports the whole apparatus, but hey if you're in a pinch, go for it!  I would print backup mounts if this tripod mount is going straight into plastic.

Lens Choices:

• Please refer to TR Richardson's Page regarding choosing lenses:
  •  https://richardsont.people.cofc.edu/safe_solar_folder/large_image_SSV.html
  • Choosing lenses is tricky because they often go out of stock.  Get the lenses as early as you can!
• My lenses (for reference only).  Choose the lenses that match your budget and what is available.  Note: the main objective lens i used is currently out of stock.
  • Main Objective - L14233
    • https://www.surplusshed.com/pages/item/L14233.html
    • 80mm diameter x 600mm focal length f/ratio 7.5
    • This lens came with a large plastic mount.  I initially tried to create my mounts using this included mount, but I found it much easier to unscrew the included lens mount and just create the whole mount myself.
  • Barlow - L1829
    • https://www.surplusshed.com/pages/item/L1829.html
    • DCV Lens 28mm diameter x -20mm focal length
    • Per the TR Richardson page regarding lenses, this lens is a much larger diameter than is necessary, but since the price doesn't really change for the barlow since it is a small lens, I went with the larger diameter so I wouldn't have to worry about melting mounts as much. 
  • FYI: the image is being projected on a 8"x10" canvas board in my pictures.  I believe I could easily project this image further back for an even larger image for the April 8, 2024 eclipse.

BOM:

• Tripod
  • Preferably one with a strong ball head.  
  • I tighten the ball head just enough that I can still move the pole around but it will hold when I let go.
• A rigid pole
  • I used a 4 foot fiberglass pole that is also extendable.  For the October 14th eclipse I mounted everything to the main, yellow, section of the pole, but you could easily mount the screen to the extendable section to allow for variable image size.
  • I guess you could use any rod or pipe as long as it is rigid enough :)
• Brass Heatsets
  • m3 heatset
    • m3x5x4 - x14
  • Tripod Mount Heatset 
    •  ¼"-20 heatset (≤ 8mm long) OR m5 x 8mm (d) x7mm (L) heatset
    • The standard tripod screw is ¼"-20.  I didn't have a ¼-20 heatset so I could mount directly to the tripod screw.  Instead I used a 5mm heatset with a m5x16mm button head cap screw with a printed washer.
    • There are two heatset holes on the tripod mount so you can use two bolts if you're worried about the mount not being strong enough.  I made it through the eclipse with one bolt.  
• 2020 extrusion
  • You know you have one laying around :)  It just needs to be longer than your screen. 
  • Tap the end of the extrusion with a m5 tap (or carefully use an m5 bolt to make a thread). 
• m3 screws (various lengths)
  • Lens mounts use (8) m3x16mm
  • Screen holder uses an m3x8mm
  • Barlow cardboard holder uses (4) m3x8mm
  • Main Lens Holder uses (2) m3x30mm
• m5 Button Head Cap Screw
  • m5x12 or 16 if using a m5 heatset to mount the tripod to the solar viewer.
    • length will depend on the mounting system you are using.  
  • m5 x 8-12mm
    • to mount the 2020 extrusion to the screen holder.
• m3 t-nut
  • mounts the piece that holds the top of the screen to the 2020 extrusion.  There are printable versions of t-nuts that you can use if you don't have one of these.
• Screen
  • I used an 8"x10" canvas panel that I had laying around.  
  • Default parameter MaxImageDiameter is 220mm = 8.6 inches.  
  • If you intend to have a larger projected image, make sure to increase the MaxImageDiameter to make the lens mounts longer.
• Piece of cardboard
  • Use the sandwich plate part of the barlow mount as a template to mark spots for holes on the cardboard.  Mount it as close to the pole as possible.

Thanks!  If you have any questions or find any mistakes i made, don't hesitate to ask/comment!