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The Digital AstroImaging Section provides a focal point for Society Members with an interest in capturing and processing digital astronomical images. Self-help Workshops are organized to assist novices and “old hands” to develop their imaging skills. Regular imaging competitions also help to promote the activities of the Section and to challenge the skills of our Members.
Feb 20 April 16 June 18 August 13 October 8 December 10 Members interested in participating in the Section’s activities and in attending a monthly meeting should contact the ASNSW's Digital AstroImaging Section Leader .
The workshops cover the basics of digital imaging, suitable cameras (including webcams, consumer digital cameras, as well as traditional cooled astrocameras) and how to connect the cameras to telescopes. Issues of field of view, resolution, exposure time and thermal noise are reviewed and techniques for calibrating, aligning, stacking and enhancing the images are introduced. Some of the free and low cost image processing software is described.
ASNSW Member Kevin Cooper captured this image of M83 from near his home in Coonabarabran. Kevin's image was captured with an SBIG ST-7E NABG CCD camera fitted with a CFW8 filter wheel on and guiding a 20 cm SCT plus an f/6.3 focal reducer on a Losmandy G11 mount.
The camera control and most of the processing was with MaxIm DL/CCD with some minor adjustments in Photoshop. The red and green components were a total of 40 minutes each and the blue a total of 64 minutes, all unbinned.
The ST-7 is a self guiding camera. It has 2 CCDs - one for imaging and one for setting on a guide star. It sends corrections to the telescope mount under the control of the computer camera control software. The 40 minute and 64 minute exposures were 4 x 10 minutes and 4 x 16 minute exposures (the imaging CCD is less sensitive to blue light). The sets of exposures are summed to give the total exposure for each filter.
This image of the Keyhole Nebula near Eta Carinae was captured (from a light-polluted northern suburb of Sydney!) with a non-cooled Canon 10D Digital Single Lens Reflex Camera (3072x2048 pixels). The camera was mounted at the prime (Cassegrain) focus of a Meade LX200 GPS 300 mm telescope (f/6.3 reducer) and relied only upon the self-tracking of the Meade equatorial wedge mount (ie no “auto-guiding”).
In order to remove thermal pixel noise, nine dark frames were median-averaged in ImagesPlus to prepare a Master Dark Frame for calibration of the light (image) frames. The final image was produced by “adaptively adding” 23 x 30 second calibrated images in ImagesPlus – a dedicated (but relatively low cost) astronomical image processing software package. The co-added image (equivalent to a single 11.5 minute exposure) was cropped and the contrast and brightness were further enhanced using the digital development algorithm in ImagesPlus.
Richard Jaworski captured this sunspot using an inexpensive webcam and a Baader Film solar filter. The technique for this type of imaging is to capture a short video file and then to “stack” a series of selected sharp video “still” frames to produce a single still image. Easy-to use software is freely available on the web to assist in aligning, cropping and stacking the images (eg Registax, Astrostack).