Venus Amateur Observing Project
Observing LogsKey details of images must be recorded for the data to be useable. Therefore an observing log should be kept which records the following data:
Dark & Flat FieldingAlthough many observers do not routinely perform dark & flat field correction to planetary images, the validity of images is improved using this method especially when faint atmosphere features are detected. Dark fields should be taken using the same exposure settings as for actual images, but with the optics covered to prevent light reaching the camera. For the exposures likely to be used for most Venus imaging dark current is unlikely to be a significant concept except for UV imaging where higher gain settings and longer exposures are necessary.
Flat fields should be taken at approximately 2/3 the linear range of the detector chip. Flat fields can be taken either of the daytime sky, a white screen held over the telescope aperture or the inside of a telescope dome.
Image ProcessingImage processing can be performed with a variety of freeware and commercial software applications. For digital video data the freeware Registax (http://registax.astronomy.net/) is a highly recommended tool for processing, since this permits automated selection, stacking & post processing of images. Additionally, dark & flat field images can be automatically subtracted from the video stream.
Image processing should include selection of sharp individual frames from video, followed by alignment & stacking of individual images to reduce noise. Generally post processing using wavelets or unsharp masking is required to reveal fine detail. However, care should be taken during processing to prevent introduction of processing artifacts.
Digital Video Imaging