Contents
- Index
Light Frames
Light frames are the main goal of everything we are doing - this is our "data". Assuming color data is desired, we need to take data through appropriate filters if using a monochrome camera, make sure focus is maintained for each filter, be aware of the differing atmospheric extinction for each filter and properly combine the color data appropriately for the given filters and sensor quantum efficiency. CCDAutoPilot can help with all of these requirements but you must make some tactical decisions. One of the first is whether to use Staircase or Shuffle for image acquisition
Staircase Acquisition
Here you acquire data that is least impacted by atmospheric extinction at lower altitudes and that which is more impacted at higher altitudes. Red and Green data is least impacted (that is why the setting sun is yellow) and Blue and Luminance is most impacted. In a typical LRGB imaging approach, the L data provides the resolution information and the RGB provides the color information. Using the letters R, G, B, L to represent the color or clear frames, Staircase acquisition would be something like:
RRR GGG BBB LLLLLLLLL BBB GGG RRR
The goal would be to center the L frames on the meridian crossing to optimize the critical luminance data. If the meridian crossing does not occur in the middle of your available dark time, you could do something like this:
BBB LLLLLLLLLLLLLL BBB GGGGGG RRRRRR
One disadvantage of Staircase is of clouds roll in at some point in the evening, you might not have a complete data set from which to assemble the data. The advantage is you have an optimally acquired data set by minimizing the effect of the atmosphere as much as possible.
Shuffle Acquisition
Here, the data is acquired sequentially so that you always have enough data to assemble an image. It would look like this:
LRGB LRGB LRGB LRGB etc.
Here you have data after the first set and the longer you go, the more data, and presumably the better SNR you get. The disadvantage here is that your critical L data is at varying altitudes and therefore subject to varying atmospheric effects due to seeing and air mass. A secondary consideration is that when you determine your RGB combine ratios, the RGB data was taken at varying altitudes so atmospheric extinction correction becomes tedious.
Color Combine Ratio
Assuming you have an accurate color combine ratio measurement for your OTA/Filters/Camera, you will need to correct your data for atmospheric extinction impact on each data frame. CCDAutoPilot, Professional Edition (only), keeps track of each color frame's altitude for you. If you have previously obtained your color combine ratio either automatically via CCDAutoPilot or manually enter it, CCDAutoPilot will provide the extinction corrected color combine ratio for each target, whether you used Staircase or Shuffle Acquisition.