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
- 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
Special thanks to Holger Weber for all his support during the review phase.