Introduction

The one-shot color all sky cameras are simple CCD cameras with fish-eye lenses. They are small, run on commercially available software and are therefore easy to deploy in remote sites. Due to slow network connectivity in most remotes sites, the real-time data is limited to sub-sampled JPEG images, while the full sized raw data are stored on disk drives at the remote sites. A block diagram of a typical system is shown below. A system includes a sun shade to keep the sun from shining directly on the CCD (possibly causing damage).

Optics

The lens is a 190 degree fish-eye lens with a c-mount interface. The lenses were made by OCI for military applications. (if you know where there are more we are interested in acquiring them...)

Detector

The detector for these cameras is a Sony ICX285AQ CCD. It is a 2/3 inch format detector with 1392 x 1040 active pixels. The pixels are arranged in a Bayer format, with rows of alternating Green/Blue pixels, alternating with rows of alternating Green/Red pixels. The pixels are 6.45 microns square. The CCD is packaged by Starlight Xpress, which provides power to the CCD and a USB interface to transfer the images.

Data collection and format

The controlling software is a Microsoft Visual Basic program that interfaces with MaxIm DL, a commercial amateur astronomy image collection software package, to collect and store the images*. Images are collected without binning and stored in the Flexible Image Transport System (FITS) format. Images are 16-bit, uncompressed and have an ASCII header. Each raw image is 2,900,160 bytes.

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*The Visual Basic program was written so that there was software control of the sun shade, however future deployments may revert back to having the sun shade actuated with a photo-relay and return the controlling software to VBscript which is somewhat more reliable.
Last modified: Mon Dec 29 16:22:26 AKST 2008