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Figure 5.8. Johannes Schedler's imaging setup. In this case the Celestron C11 is being used to image with the Canon 10D and the TMB refractor for autoguiding.
I have found that combining a large number of jpg-fine images does not show a major disadvantage compared to using the raw mode. "Extended adding" of 16 calibrated 8-bit images in the 16-bit-per-channel space increases the dynamic range of the final image from 8 to 12 bits. This compensates for the limited dynamic range of the 8-bit-per-color jpg files. A second advantage of the "extended adding" is the combining of different exposure times, i.e., for M42 exposures of 20 sec, 60 sec and 300 sec can be added together in one step. This procedure is much easier than difficult masking procedures for the burned-out areas (see Figures 5.10 and 5.13). The calibrated combined images should be saved in 16 bit tiff format, then a DDP processing (i.e., in ImagesPlus) supplies the desired nonlinear stretching. Further processing steps, like removing gradients and adjusting the color balance, I prefer to do in Photoshop. In most
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Figure 5.10. Adding exposures of different lengths preserves the detail that would otherwise be burnt out in the brightest areas. This image comprises crops of 3 raws from the left to right that have been added in the following way: 2 x 20 sec, 8 x 60 sec and 26 x 5 min. The final combined result is shown in the image crop at right. The telescope was the 4-inch TMB refractor with reducer at f/5.
cases a noise reduction program like Neatimage helps in smoothing the final image.
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Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.