#!/usr/bin/env python
# coding: utf-8

# # Calibration choices you need to make

# There are a few choices you need to make about how you will calibrate your data.
# Sometimes the decision will be made for you by the data you have.

# ## Subtract bias and dark as separate steps or in one step?
# 
# Every dark image contains bias when it comes off of the camera, so in principle
# you can take care of both bias and dark by constructing a master dark image that
# leaves the bias already present in the dark images in place.
# 
# This only works if for every image from which you need to remove dark currrent
# you have a master dark of exactly the same exposure length.
# 
# If not, you need to produce master dark images with the bias removed so that
# they can be scaled by exposure time.

# ## Subtract overscan or not?
# 
# This is only applicable if your images have an overscan region. Subtracting
# overscan can be useful for removing small (typically a few counts) variations
# from image-to-image over the course of a night.