|ZWO ASI 174MC colour USB 3.0 camera. Image from ZWO website.|
- No mechanical shutter to wear out.
- The large pixel size (5.86um) should give good sensitivity.
- The sensor has an IR cut-off filter fitted (filters cannot be used with the fish-eye lens).
- The manufacturer provides support to access the camera from Linux.
I've written a short demo program to illustrate how to access the camera from Python. The camera can operate in two modes. The first, snapshot mode, takes a single exposure. The second, video mode, continually takes exposures which can be downloaded from the camera as and when required. At first glance either mode would appear suitable for the purpose of taking a single exposure once a minute. My main concern is how to set the exposure correctly for an automated system which will run in a variety of different lighting levels (twilight, nighttime, and possibly even daytime). Fortunately this particularly camera provides an auto-exposure mode which can adjust the exposure time and gain settings according to the ambient light levels. It does this by analysing the image histogram after each exposure. The documentation doesn't explain the auto-exposure mode but I suspected that the camera would have to be operated in video mode for this to work. A quick test proved this to be the correct. How well the auto-exposure algorithm works at night has yet to be discovered; since it is an astronomy camera I'm optimistic that it will be suitable and save me from having to implement an exposure control algorithm.
|Sample image from ASI174MC and Fukinon FE185C057HA-1 2/3" fisheye lens.|