Daily Image
07-01-2010
A Rose in Winter
| Submitter: | Albert van Duin |
| Description: | Imaging deep sky objects from a village is getting increasingly difficult due to light pollution these days. One solution is decreasing the observed bandwidth to get a better signal to noise ratio. The Rosette-Nebula is a well known object for astrophotographers, it is located a bit to the east of the well known constellation of Orion. For my observatory it is positioned quite low in the souhtern sky, a very unfavourable location since the biggest part of the village of Beilen is located in that direction. The Rosette-nebula glows in the deep red colour of H-alpha (656.3nm wavelength). By using a 6nm bandwidth interference filter, the contrast between the nebula and the sky background can be improved a lot for my camera, which is sensitive from 400-1000nm. Twelve images with 10 minute integration time were made in 2x2 binning (2x2 pixels combined before read out) to increase sensitivity, but at the cost of resolution. After each exposure the position of the guidestar was changed at random ever so slightly, to change the pointing of the telescope a fraction of a pixel. This process is called dithering. Afterwards the images were calibrated with darkframes and flatfields, and next the images were resampled by a factor of 2. Finally they were aligned and stacked. This process, called drizzle combining, results in an image that has nearly the full resolution of an unbinned image, but with the benefit of an increased senstivity. |
| Copyright: | Albert van Duin |
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