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An Artificial Variable Star Simulator

An Artificial Variable Star Simulator. Doug Welch, McMaster Anthony Tekatch, Unihedron Steve Bickerton, Princeton. Why Simulate?. Laboratory exercises Training Ground truth for KBO occultation studies Control studies Observer differences Biases Temporal Color Scintillation

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An Artificial Variable Star Simulator

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  1. An Artificial Variable Star Simulator Doug Welch, McMaster Anthony Tekatch, Unihedron Steve Bickerton, Princeton

  2. Why Simulate? • Laboratory exercises • Training • Ground truth for KBO occultation studies • Control studies • Observer differences • Biases • Temporal • Color • Scintillation • Exhibits

  3. Prior Art “Observing simulated Cepheid variable stars in an introductory astronomy lab” Flesch, TR 1979, Am J Phys, 47(3), 232 • Telescope + photomultiplier tube! • Incandescent bulb + function generator • Single star (source) • One pulsation cycle, two filters

  4. Prior Art “Observing variable stars indoors with a microcomputer and phototransistor” Rafert, JB, and Nicklin RC 1983, Am J Phys, 51(7), 668 • “Telescope” + phototransistor • Incandescent bulb + Nerf ball! • Incandescent bulb @ 120 Hz = pulsar!  • Single system (source) • Oscilloscope output

  5. Gene Hanson’s Variable Star Light Board http://www.genehanson.com/lightbd.htm • 14.4V incandescent bulbs • Large board • SS Cyg field • Manual http://www.genehanson.com/images/brdfrtg6.jpg

  6. Developments • Small, efficient white LEDs • Only prior choice were incandescent bulbs • “Color temperature” now similar to stars • Roscolux filters for cooler stars • Fast microcontroller clocks • 40 MHz = 10 million instructions per second • Decent amount of microcontroller memory • 24 to 32k instructions/lookup tables

  7. Scintillation (1/f noise) Gaussian (“white”) 1/f (“flicker”) 1/f^2 (“Brownian”) Time series from: http://ozviz.wasp.uwa.edu.au/~pbourke/fractals/noise/

  8. Hardware • PIC 18F4525 or 18F4620 MCU • MAX 233 serial interface chip • 4-to-16 decoder • ULN2803 driver • Use of In-circuit Serial Programming

  9. Future Plans • Increase number of LEDs to 128 • Self-calibration with TSL237 • Individual LED current-to-flux correction • Display time for use with labs • Analog generation of scintillation noise? • Substitute computer+ethernet control for dedicated microcontroller?

  10. DEMO

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