Video Digitising Systems

We are digitally imaging all known southern stellar Herbig Haro complexes selected from Reipurth's Catalogue of Herbig Haro objects (Reipurth 1994) using a low cost PC/AT video digitising system. This system has been developed at the Department of Physics of the University of Wollongong from commercially available hardware and software.

The image digitising facility provides for the real time, 8-bit (256 grey scale), video digitising and analysis of photographic plate material (Zealey et al., 1994). The image digitiser system uses a PC/AT based video frame grabber.

The digitising board used is of PCVisionPlus type. Computer controlled Look Up Tables (LUT's) allow the stored 512512 pixel image to be displayed in pseudo colour on a dedicated RGB image monitor. The video digitiser accepts video input from a Philips CCD video camera mounted on a Polaroid Laboratory Camera and a combination of lenses allows for both wide-field (300 mm square; 6 mm pixels) and microscopic (5 mm square; 10 m pixels) imaging.

Plate illumination is provided either by a Chromega colour enlarger head for regions up to 5 cm square or a light box for larger areas.

Jandell's JAVA software allows real time enhancement and measurement of the digitised images. JAVA allows for spatial filtering, contrast enhancement, thresholding, simple backgrounding and source counting as well as photometric analysis. Images are stored as 8 bit TIFF (Tagged Image File Format) which are readable by a wide range of image software. Once images are captured from the screen, they are stored on a 600 Mb Ricoh Magneto Optical Drive and then copied onto floppy disks for transfer to other PCs with specialised imaging software. Image editing is done on JPL's Alchemy Mindworks GWS package which is useful for a first look at the images, cropping and scaling and conversion to GIF (Graphic Interchange Format) or other image formats. Further enhancement and addition of text is done in CORELDRAW or Adobe Photoshop.

© Copyright Astronomical Society of Australia 1997