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

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

THE Book To Get…..

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)

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 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

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

Telescopius.com – Image Scale Tool for your equipment options

SharpCap Polar Alignment Tool

SharpCap Bahtinov Mask Focusing Tool

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

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

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

Live Stacking – Histogram Tab

Live Stacking – Stacking Tab

Live Stacking – Guiding and Dithering Tab

Live Stacking – FWHM Filter Tab

Live Stacking – Brightness Filter Tab

Live Stacking – Log Tab

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

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

Examples of Imaging Issues

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.

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.

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

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

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

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

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