1. Deep Sky Imaging with SharpCap
Mark W. Poole
6/18/2019

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)

8. My Process
Capture a library of Dark Frames beforehand at my anticipated gain/exposure settings
Use 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 SharpCap bahtinov 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

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

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

11. SharpCap Polar Alignment Tool

12. SharpCap Bahtinov Mask Focusing Tool

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

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

15. 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

16. Live Stacking – Histogram Tab

17. Live Stacking – Stacking Tab

18. Live Stacking – Guiding and Dithering Tab

19. Live Stacking – FWHM Filter Tab

20. Live Stacking – Brightness Filter Tab

21. Live Stacking – Log Tab

22. RemotePC Window (inside the house!)
Both computers connect to the internet through my wireless network
FREE to control one system (

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

24. Examples of Imaging Issues

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

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

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

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

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

30. Resources Explore Scientific www.explorescientific.com
Celestron
Starry Night software
ZWO Cameras
Optolong Filters
Telescopius deep sky target info
SharpCap imaging software
PHD2 guiding software
RemotePC software
PhotoShop photo editing
Imaging forums

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