A science image or science frame is a (image/)frame that has been calibrated to the top-of-atmosphere a.k.a. one whose data have been reduced. It is only from these frames that you can estimate most physical quantities.

Entire Pipeline

The term reduction refers to the removal/reduction of extra counts collected in light frames. An appropriately run data reduction pipeline accounts for the effects of the optical system, detector, and atmosphere.

The optical system and detector introduce non-uniformities in how radiant energy is collected as well as extra signal from the electronic components in the detector owing to voltages necessary for the operation of the detector as well as erroneous voltages generated by thermally agitated electrons. These three effects are handled by specially collected calibration frames (usually multiple FLAT and DARK frames). Properly addressing these results in a light frame that represents (to the best of our abilities) the collected radiant energy that was incident on the primary optical device of our optical system (i.e., the 0.8 m primary mirror).

The atmosphere introduces some extra radiant energy owing to light pollution herein referred to as 'sky brightness'. Additionally, the atmosphere removes some radiant energy that would otherwise reach the detector via a process called 'atmospheric extinction'. Properly addressing these results in a light frame that represents (to the best of our abilities) the radiant energy that would have been collected were the detector at the “top of the atmosphere” (i.e., outside the bulk of the atmosphere).

As such, this documentation outlines the data reduction process as two distinct parts. Data Reduction to Energy Incident on Telescope & Data Reduction to Energy Incident at Top-Of-Atmosphere.

Reduction to Telescope

Reduction to TOA

Get Magnitudes

• Data Reduction
• Astrometric Calibration
• Photometric Calibration