An Image Combination Example

To illustrate the relative merits of the two methods compared above, some deep HST NICMOS camera 3 imaging at 9 dither positions were combined using both ACOADD and Drizzle as the combination engines. The results are shown in Figure 2 for two different parameters in each case. For all images the output image had a pixel spacing which was three times as fine as that of the input. The contrast and slight resolution enhancement offered by ACOADD is clear as is the strongly correlated noise speckling in the background.

 

Figure 2: A comparison of combinations of deep HST NICMOS Camera 3 data. There were 9 evenly-spaced dither positions. The upper combinations were done with Drizzle and the lower ones with ACOADD. The upper left had pixfrac=1.0 and the upper right pixfrac=0.5. The lower left was smoothed with a Gaussian of $\sigma=1.0$ output pixels and that at the lower right with $\sigma=0.7$. Data courtesy Mark Dickinson (STScI).