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Camera Comparison Signal Level and SNR

Steve Conard Willow Oak Observatory, Gamber, MD International Occultation Timing Association (IOTA) Oct 20, 2012. Camera Comparison Signal Level and SNR. Disclaimer.

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Camera Comparison Signal Level and SNR

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  1. Steve Conard Willow Oak Observatory, Gamber, MD International Occultation Timing Association (IOTA) Oct 20, 2012 Camera ComparisonSignal Level and SNR

  2. Disclaimer • Bruce, Russ, and I had originally hoped to do a thorough comparison of several video and digital interface cameras that could used for IOTA’s observations • Due to personal time limitations and weather, we didn’t accomplish what we had intended • It became a much a less controlled test, with fewer cameras, than we had originally intended • View it as a quick comparison of several common cameras as typically used in real-world conditions

  3. Disclaimer • Data collection was not as well controlled as I had hoped • Intended to have a parallel telescope recording the same field at the same time • Did not take the time to fully learn to use the Flea camera—resulting in only 8-bit data collected • The data have not rigorously been analyzed, and may contain errors • More data is available to be analyzed when time permits

  4. Test Hardware • C-14 on CGE mount • Focal reducer used to set f/number at about 4.0 • In roll-off observatory • Video data through IOTA-VTI to Canon ZR-65 recorder • Flea data through Firewire to desktop PC

  5. Cameras • “Control” was a Stellacam EX (my SN 01) • Other video cameras • Stellacam EX (SN 02) • Watec 902 Ultimate (SN 01 and 02) • PC164C-EX2 • Firewire camera • Flea 3 FL3-FW-03S3M-C • All arrays are ½” format except the PC164C-EX2 which is 1/3”

  6. Method • Used same field for each camera • EplisonLyra (“Double Double”) selected to have easy reference, and was fairly high in the sky • Reference camera used before and after to look for changes • Tried to pick nights with good transparency and no visible clouds • Tangra used for data analysis • Used auto aperture selection • Picked up to 6 stars for comparison

  7. Video Cameras Only • Weather clear, reasonable transparancy • Tangra apertures left to automatic selection • Collected data with Stellacam EX 1 at 1 and 2 fields integration • Collected data all other cameras • Varied gain on one Watec • Used 1 and 2 fields on the second Stellacam EX • Collected data with Stellacam EX 1 at 1 and 2 fields integration • Only minor difference in signal before/after with Stellacam EX 1

  8. Signal Level

  9. SNR

  10. Sample Images Stellacam EX SN 1 Before Stellacam EX SN 2

  11. Sample Images Watec 902 Ultimate SN 1 Watec 902 Ultimate SN 2

  12. Sample Images PC164C-EX2 Stellacam EX SN 1 After

  13. Discussion • PC164C-EX2 may give the best combination of SNR and signal level • Significantly better at all but the brightest targets, where SNR may fold over (may not be the best choice for a bright asteroid over a fainter star) • It also may have other issues that weren’t investigated here • Watec 902 Ultimate and Stellacam EX’s are very similar • Watec can produce almost as much signal as the PC164C-EX2 when the gain is very high

  14. Flea vsStellacam 30 Hz • Weather clear, reasonable transparancy • Tangra apertures left to automatic selection • Collected data with Stellacam EX 1 at 1 and 2 fields integration • Collected data with Flea 3 • Max’ed out the gain at 24 dB • Maximized exposure time at a 30 Hz readout rate • Important: Flea was used in 8 bit mode • Collected data with Stellacam EX 1 at 1 and 2 fields integration • Only minor difference in signal before/after with Stellacam EX 1

  15. Signal Level

  16. SNR

  17. Sample Images Stellacam EX 2 Fields Flea 3

  18. Discussion • Stellacam has much larger signal level • This may not be true with Flea at 12-bits • Roughly the same SNR for fainter targets, possible advantage to Flea for brighter ones

  19. Flea vsStellacam ~2 Hz • Weather clear, reasonable transparancy (same time as video comparison above) • Collected data with Stellacam EX 1 at 32 fields integration • Collected data Flea at 1.875 Hz, max exposure • Gain at 24 dB • Flea at 8 bits • Collected data with Stellacam EX 1 at 32 fields integration • Only minor difference in signal before/after with Stellacam for the fainter targets—the bright ones showed more change for some reason

  20. Signal Level

  21. SNR

  22. Sample Images Stellacam EX 2 Fields Flea 3

  23. Discussion • Stellacam has much larger signal level • This may not be true with Flea at 12-bits • Roughly the same SNR for fainter targets, Stellacam showing saturation on brighter ones

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