Adjustable phone holder for afocal projection astrophotography

pinshape

SummaryNotes Update - Completely rebuilt from scratch after initial testing prints failed to meet expectations. The blocks on the edges didn't quite accommodate my phone when aligned with the eyepiece, and it couldn't handle phones like Samsungs where the camera is centered. This revised version aims to be more functional. Background I am designing this for the Edmonton RASC observatory at the Telus World of Science in Edmonton. They host public observing sessions on good weather days, and many passersby stop by the park. Inevitably, someone wants to take a photo with their phone. Idea Since we can't predict which phone will be used, I've transformed the design for the Minikossel holder into an astronomy outreach tool. This device is intended for use with an eyepiece already in place - it won't fit directly into the focuser. Estimated dimensions for a 2-inch eyepiece are approximately 2.2 inches OD at the spot where the eyecup normally fits, while a similar guess was made for the 1.25" version. I'll refine these measurements once I have actual numbers. Instructions I plan to print this in black ABS plastic. The interior of the optical path will be sanded with 60-grit sandpaper to eliminate internal reflections and add micro-baffling. Nuts and screws will be required for the sliders, which I'll likely use wingnuts or similar for easy adjustment. There are designated spots for adding set screws to secure it firmly on the eyepiece. This piece is designed for a camera in the upper right corner of the phone, like an iPhone. I've attempted to leave room for some variation but haven't used many other phones, so I make no promises. The .scad file is parameterized and should be somewhat adjustable. The updated design doesn't have lips to grasp the phone; instead, I plan to attach craft foam-rubber sheet for grip. I previously tried using felt pads, but they're too slippery. The rubber bands should hold it in place. Both your phone and eyepieces could be damaged by using this - not my responsibility.