3D Printed Telescope Spider

I am designing and building a homemade telescope, loosely following designs from here. While a lot of their components are ingeniously designed, I wasn’t satisfied with the spider plans they provided. I decided to try my hand at designing my own spider in Fusion 360 (using their free enthusiast subscription) and 3D printing it.

The spider snugly fits in an 8″ diameter tube. There are 3 slots in the perimeter to allow rotational alignment along the axis of the tube. There are 3 additional screws in the central cylinder that tilt the diagonal mirror holder and provided height adjustment. The diagonal holder has multiple grooves to provide more surface area for the silicone to bond to. The surface the mirror mounts on is on a 45. The entire thing was printed in PLA on Mark’s SOM printer (huge thanks to Mark for helping out).

A similar design could be constructed in the machine shop with multiple operations and perhaps even some welding, but the ease of designing this in Fusion 360 along with the little setup involved in the 3D printing process made this an ideal path to choose.

Experiments in optics and image processing

After successfully mating a web cam with my microscopes (http://www.thingiverse.com/thing:216821) and telescope (https://www.youmagine.com/designs/web-cam-adapter-for-meade-telescope-eyepiece), I decided to design and print adapters to mount my Droid Turbo phone on the same scopes (https://www.youmagine.com/designs/microscope-adapter-for-droid-turbo-phone and https://www.youmagine.com/designs/droid-turbo-phone-to-telescope-adapter) so I could shoot higher resolution stills (21 Mp) and 1080p (and even 4k) video.   The telescope adapter fits over a Meade 32mm focal length Super Plössl eyepiece and provides about 47X magnification with the telescope.  I printed a similar adapter for my surgical microscope.














The telescope adapter firmly grips the phone and the eyepiece.















Initial tests were a little disappointing.  The combination of the phone’s camera and the telescope’s optics has significant pincushion distortion.  The image has only been mirrored L-R and scaled down (original is 21 Mp).  Note the lack of contrast (looking through 1/2 mile of humid air) and the curves in the power line and pole, and even the grass line:

pinch test original










A quick search found that the Gimp has built in transform tools to correct (or create) lens distortion.











It only took a couple minutes of messing around to get acceptable results.  Here’s the same image with the pincushion distortion corrected (whole image), contrast stretched and white balance corrected (rectangular area).  The pole, power line, and even the grass line now look straight.

pinch test corrected










And here’s the final image with all corrections and cropping applied:












Next step: photograph known square grids through the microscope and telescope and then create and save some preset corrections to apply with Gimp.

I wonder if something like this exists for video.  Hmmmmm…