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Deep Sky Imaging with SharpCap

Deep Sky Imaging with SharpCap. Mark W. Poole 6/18/2019 poolemarkw@aol.com. Some Definitions. Light Frames – images of your desired object

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Deep Sky Imaging with SharpCap

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  1. Deep Sky Imaging with SharpCap Mark W. Poole 6/18/2019 poolemarkw@aol.com

  2. Some Definitions • Light Frames – images of your desired object • Dark Frames – images taken at the same settings as your light frames but with the aperture covered to capture inherent thermal noise and hot pixels for removal • Flat Frames – images captured using a dim light source to capture vignetting and dust motes for removal • Bias Frames – images captured at the same gain as lights but shortest exposure possible to capture the base noise level of each pixel for removal • Auto-Guiding – using a separate telescope and camera to very accurately track a star near your desired object, allowing for long exposures without blurring • Dithering – randomly shifting the telescope just a few pixels between light frames to prevent fixed pattern noise • Plate Solving – software that compares your current camera image with a library of pictures to identify exactly where your camera is pointing and then direct your mount to perfectly center an object • Stretching – post processing that increases the range between your darkest and lightest areas of the final image

  3. THE Book To Get…..

  4. Primary Imaging Setup • Explore Scientific 127mm FCD100 refractor (F/7.5) • Field Flattener or Flattener/Reducer • Celestron CGEM II equatorial mount • Starry Night laptop mount control software (free w/ mount) • ZWO ASI071MC Pro camera cooled to -10C • Optolong L-Pro light pollution filter • ZWO 60mm guide scope • ZWO ASI190m mini guide camera • PHD2 auto-guiding software (free) • Home-made 12V dew heater strips • SharpCap imaging software ($15/year) • RemotePC remote control software (free for one computer) • 5A power supply for the CGEM mount • 10A power supply for dew heaters and camera cooling • Photoshop CC Subscription ($10/month)

  5. My Process • Capture a library of Dark Frames beforehand at my anticipated gain/exposure settings • Use www.telescopius.com to determine image capture timing and desired focal length • Rough polar alignment with polar scope • Detailed polar alignment with SharpCap and guide scope (excellent tool!) • Celestron 2-star alignment with two calibration stars (plate-solving will shorten this) • Start Starry Night to control the mount • Install imaging camera, choose that camera in SharpCap • GoTo the desired object, rough focus, and rotate the camera to get the desired image orientation • GoTo a bright star nearby and do a detailed focus using SharpCapbahtinov mask tool (excellent!) and lock the focus • Slew back to the desired target and center (plate solving will shorten this) • Start PHD2 auto-guiding • Capture Flat Frames (30) • Determine and set desired gain/exposure for the light frames using SharpCap histogram tool • Start SharpCap Live Stacking • Monitor FWHM Focus Scores, pause and adjust if rising (temperature dropping) • “Save” every 30 minutes • “Hibernate” the mount for the next night! • Post-Processing in Photoshop

  6. Telescopius.com – Interactive Rise, Transit, Set, and Elevation chart

  7. Telescopius.com – Image Scale Tool for your equipment options

  8. SharpCap Polar Alignment Tool

  9. SharpCapBahtinov Mask Focusing Tool

  10. Exposure Time Recommendations - Determined by F/Ratio, sensor noise, and darkness KPP Back Yard East

  11. Gain Setting? • Camera-dependent graphs, see manufacturer data • Higher gains decrease noise but you lose dynamic range

  12. Sensor Temperature? • Camera-dependent graphs, see manufacturer data • Cooler may not be able to reach low temps on hot nights This is why we want cooling! No real advantage to going lower

  13. Live Stacking – Histogram Tab

  14. Live Stacking – Stacking Tab

  15. Live Stacking – Guiding and Dithering Tab

  16. Live Stacking – FWHM Filter Tab

  17. Live Stacking – Brightness Filter Tab

  18. Live Stacking – Log Tab

  19. RemotePC Window (inside the house!) • Both computers connect to the internet through my wireless network • FREE to control one system (www.remotepc.com)

  20. Photoshop Post Processing Raw Stack Crop Tool Curves Tool Levels Tool Camera Raw Filter Tools Astronomy Tools Add-On After Stretching

  21. Examples of Imaging Issues

  22. Blurred/enlarged stars due to bad focus. Use a Bahtinov mask and monitor the FWHM score through the night.

  23. Football stars going the same direction due to inadequate tracking. Need to do a better polar alignment, autoguide, or shorten exposure duration.

  24. Football stars going outward at the edges due to incorrect back focus of flatteners/reducers. Measure accurately and test.

  25. Vignetting due to the optical train. Capture and use flat frames.

  26. Fixed pattern noise from our camera. Use dithering with your autoguiding.

  27. Resources • Explore Scientific www.explorescientific.com • Celestron www.Celestron.com • Starry Night software www.starrynight.com • ZWO Cameras www.astronomy-imaging-camera.com • Optolong Filters www.optolong.com/en/ • Telescopius deep sky target info www.telescopius.com • SharpCap imaging software www.sharpcap.co.uk • PHD2 guiding software www.openphdguiding.org • RemotePC software www.remotepc.com • PhotoShop photo editing www.adobe.com/products/photoshop • Imaging forums www.cloudynights.com

  28. Questions? Mark W. Poole poolemarkw@aol.com

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