ROBOTIC STAR TRACKER
ROBOTIC STAR TRACKER
A custom camera mount for detailed astro images
A custom camera mount for detailed astro images
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2019-2022
OVERVIEW
OVERVIEW
Since high school, one of my favorite hobbies has been astrophotography, which is the art of capturing images of objects in the night sky such as nebulae, galaxies, and star clusters. Though I enjoyed the hobby, my lack of equipment (and lack of funds to buy equipment) made the capture process slow and tedious.
STAR TRACKERS
STAR TRACKERS
One piece of equipment that is necessary for taking detailed images is a start tracker. A star tracker is, in short, a motorized camera mount that rotates at exactly the same speed as earth’s rotation. This effectively cancels out earth’s rotation and allows for very long exposures (up to 3 minutes!).
MOTIVATION AND GOALS
MOTIVATION AND GOALS
A major hurtle for me was that star trackers are expensive, with prices typically ranging between $400-$900. Due to this, I decided to build my own tracker using the two materials I had readily available: wood and Legos!
THE SOLUTION
THE SOLUTION
I built a custom star tracking system that allows me to capture exposures of up to 30 seconds. Given that the maximum exposure length without a tracker is 3 seconds, this is a 10x increase. The physical tracker is made of wood and is a modified/improved version of George Haige's "barn door" tracker design (explained below). The tracking system was implemented and programmed using a Lego EV3 motor and hub.
Timelapse of my mount in action
THE SMART TRACKING SYSTEM
THE SMART TRACKING SYSTEM
The most important feature of this tracker is self-correction. The hub (shown to the right), monitors the tracking speed and dynamically adjusts to stay in sync with the speed of the Earth's rotation.
THE BIRTH OF MY NEXT PROJECT
While designing the smart tracking system, I realized how useful automation and progress monitoring could be in astrophotography. This system has been vastly improved over the last several years, and is showcased on the "Orion" project page.
Photo of Orion Nebula, captured using my star tracker
DESIGN & PROGRESSION
DESIGN & PROGRESSION
FIRST PROTOTYPE: STRAIGHT SCREW DESIGN
FIRST PROTOTYPE: STRAIGHT SCREW DESIGN
I based my tracker off of the "Barn Door Tracker" designed by George Haige in 1978. A major disadvantage of this original design is that it must be operated by hand. Therefore the main objective of my first prototype was motorizing the mount. My initial design was built using wood scraps and knex parts.
SECOND PROTOTYPE: CURVED SCREW DESIGN
SECOND PROTOTYPE: CURVED SCREW DESIGN
While this design was technically functional, it became inaccurate after only a few minutes and was highly unstable. These inaccuracies come from the screw used in the design. Because this screw is straight, the mount can approximate the speed of the earth's rotation, but it will gradually rotate more slowly as the screw extends. For this reason, I redesigned my mount to use a curved screw and also improved the general construction of the mount. In this version, I could reliably capture exposures of up to 30 seconds.
STRAIGHT SCREW VS. CURVED SCREW DIAGRAM
STRAIGHT SCREW VS. CURVED SCREW DIAGRAM
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