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A Beginner’s Guide

A Beginner’s Guide. By Kevin Saunders. DSS Website. http://deepskystacker.free.fr/english/index.html. Lights, Darks, Flats and Bias Frames.

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A Beginner’s Guide

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  1. A Beginner’s Guide By Kevin Saunders

  2. DSS Website • http://deepskystacker.free.fr/english/index.html

  3. Lights, Darks, Flats and Bias Frames Light Frames (Subs)The Light Frames are the images that contains the real information: images of galaxies, nebula...This is what you want to stack.Dark Frames The Dark Frames are used to remove the dark signal from the light frames With DSLRs and CCD Camera, the CMOS or CCD is generating a dark signal depending of the exposure time, temperature and ISO speed.To remove the dark signal from the light frames you use a dark frame that contains only the dark signal.The best way to create the dark frames is to shoot pictures in the dark (hence the name) by covering the lens. The dark frames must be created with the exposure time, temperature and ISO speed of the light frames (resp. flat frames). Since the temperature is important try to shoot dark frames at the end or during your imaging session.Take a few of them (between 10 and 20 is usually enough). DeepSkyStacker will combine them automatically to create and use a clean master dark.Bias Frames (aka Offset Frames)The Bias/Offset Frames are used to remove the CCD or CMOS chip readout signal from the light frames. Each CCD or CMOS chip is generating a readout signal which is a signal created by the electronic just by reading the content of the chip.It's very easy to create bias/offset frames: just take the shortest possible exposure (it may be 1/4000s or 1/8000s depending on your camera) in the dark by covering the lens.The bias frames must be create with the ISO speed of the light frames. The temperature is not important.Take a few of them (between 10 and 20 is usually enough). DeepSkyStacker will combine them automatically to create and use a clean master bias/offset frameFlat FramesThe Flat Frames are used to correct the vignetting and uneven field illumination created by dust or smudges in your optical train.To create good flat frames it is very important to not remove your camera from your telescope before taking them (including not changing the focus).You can use a lot of different methods, e.g. Luminance panel, Laptop Screen, or the simplest way is to put a white T shirt in front of your telescope and  smooth out the folds. Then shoot something luminous (a flash, a bright white light, the sky at dawn...) and let the camera decide of the exposure time (Av mode). The flat frames should be created with the ISO speed of the light frames. The temperature is not important.Take a few of them (between 10 and 20 is usually enough). DeepSkyStacker will combine them automatically to create and use a clean master flat frame.

  4. DSS Calibration Process

  5. File Structure

  6. Settings - Result

  7. Settings RAW

  8. Settings FITS

  9. Settings Lights Use Average or Median < 10 Images Kappa Sigma Clipping > 10 Images

  10. Settings Darks

  11. Settings Flats

  12. Settings Bias

  13. Settings Alignment

  14. Settings Cosmetic From research I have found people using these settings. Hot Pixels = 70% Cold Pixels = 50%

  15. Settings Output Remember to change the Output Folder each time

  16. Open Picture Files

  17. Open Picture Files Use the Group Tabs to Stack Lights by Exposure Time when mising durations of Lights, e.g. Main Group 5min Lights, 5 min Darks, Bias, Flats and Group 1 0min Lights with 10 min Darks only

  18. Open Dark Files Don’t forget DSS will open the Darks from the last directory you used..VERY CONFUSING

  19. Open Flat Files

  20. Open Bias Files

  21. Register - Actions You can reduce the Select the best 100% but only if your images are less than perfect yet you still want a result.

  22. Register - Advanced Compute the number of detected stars and see what result is returned. There is a slider to move and the ideal number to get is around 50. This part is very important and I believe sets the baseline for processing algorithms. Try 12%-40%

  23. Register – Recommended Settings Click to Toggle the settings and make a change, e.g. if you have less than 10 images and Kappa-Sigma stacking selected it will recommend Average or Median

  24. Save your Stacked Image Save stacked image as a TIFF. I personally use CS6, but if getting started you can complete basic processing in DSS. DON’T FORGET TO SAVE YOPUR FILE LIST as well

  25. Basic Processing in DSS Save stacked image first as a TIFF before completing basic processing of RGB Levels & Curves, Luminance and Saturation. Remember to Link Settings for RGB.

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