Her Majesty, the SX-35
Her Royal Highness, the SX-36
Bias and Flats of our SX-36 (FITS)
Flat fields, darks, and Bias should be combined with the Median or Sigma Clip filter in MaximDL to build a master file (see screenshot). The Average filter does not remove the cosmics effectively.
- Darks: once a year. Like everything on this planet, CCD sensors change their characteristics over the time.
Example: Master dark SX-36, 20min, -15°C (JPEG/FITS).
- Bias: once a year.
Example: Master bias SX-36, -15°C (JPEG/FITS).
- Flats: each time you turn or mount/dismount your camera on the scope. As the time goes by, new dust particles sit on the optical path. Even in stationary setups it is advisable to periodically (once a year) make flats.
Example: Master flat SX-36, FSQ-85(f/3.9), -15°C (JPEG/FITS).
TIP: enable the check box "Group By Slot"when making flats in MaximDL to minimize filter wheel rotation!
Flat field panel
The final step is to calibrate your your master flats. Download my check list. Use the Median or Sigma-Clipping filter for stacking to create the master files. For those fellows making scientific work on CCD sensors without any commercial interest, I am making available the dark, flat and bias calibration frames of our new SX-36 camera (Serial No. 007, KAI-16070 sensor): frames in JPEG for preview, frames in FITS format for scientific purposes
- Acquisition of red images with this monochrome camera => RRAW
- image calibration RRAW (using the master dark, the master bias, and a R calibrated* master flat) => RCAL
- remove gradients (i.e. the light pollution) in R channel using MaximDL's "Auto remove gradient" function => Rclean
- align all Rclean images using MaximDL manual star alignment algorithm => Raligned
- stack all Raligned images using Sigma-Clip method => Rsum
- ... repeat steps 1..5 for GRAW (green) images
- ... repeat steps 1..5 for BRAW (blue) images
- align the three Rsum, Gsum, Bsum images => Rfinal, Gfinal, Bfinal
- color combine Rfinal, Gfinal, Bfinal => RGBfinal)
- has an improved S/N ratio as a stack of single exposures.
- is free of numerous artifacts due to calibration with flat fields (step 2):
- inhomogeneities of the CCD sensor.
- has no artifacts due to vignetting of the optics.
- has no artifacts due to dust particles on the telescope optics or the CCD sensor.
- is free of the bias signal (step 2).
- is free of thermal current (step 2).
- has no light pollution or moon glow gradients (step 3).
- has no satellite traces, due to Sigma-Clip stacking method (step 5).
- is in color
- has tighter stars with accurate colors
Gallery and Software
Special thanks to Holger Weber for all his support during the review phase.