Astrodon

The RGB Weight Calculator is a software application that helps you combine data taken with red, green and blue (RGB) filters using monochromatic CCD cameras.  Enter your brand of camera or detector, your brand of RGB filters and the elevation of the object in the sky and the program will determine color combine weights for equal length exposures based upon the accepted G2V "sun-like" star white-point balance. 

The program also calculates the OIII emission-line balance determined by your RGB filter set (see Goldman "Getting Star and Nebula Color Right in CCD Imaging", Sky & Telescope, July 2003, page 128).  Your color weights are determined by broadband light from stars. However, the OIII emission line near 500 nm is captured in both the blue and green filters and ideally should end up equal in your final, weighted blue and green images, leading to a blue-green, or teal color.. Depending upon the design of your filter set, the OIII balance can be skewed too blue or green.  The RGB Weight Calculator provides an estimate of  this OIII balance that you will likely see in the color of objects like planetary nebula. The above analysis shows the results for Astrodon E-Series filters used with the KAF3200ME detector in an SBIG ST10XME CCD camera.

There are lot-to-lot variations in the quantum efficiency (QE) of CCD detectors and there are variations in filter transmissions.  Therefore, the RGB Weight Calculator can only provide general guidance in combining RGB data and is not meant to replace actual measurements of G2V stars. However, actual measurements can be affected by high clouds, smoke or smog, and the RGB Weight Calculator can provide a double check. 

FEATURES 

• Stand-alone program (download only)
  
• Free upgrades when new cameras, filters are added
• Inputs for many popular CCD cameras and  filters,
• Inputs for telescope type, object elevation, light pollution filter
  
• RGB weights for equal exposures
  
• OIII balance
  
• Spectral plots of filter transmission and CCD QE
• Final flux for RGB to compare efficiencies