When you want your work to survive over time, one solution is to remove time from the equation.
One good example is the Calar Alto image we are finishing now. We have been imaging the Stephan’s Quintet compact group of galaxies during the last four years. We acquired a total exposure time of 59 hours. During 2009, 2010 and 2011 we used broadband RGB filters with the old, 4-megapixel camera. Last year, with the new 16-megapixel camera, we acquired 15 hours of high-resolution, unfiltered images; these exposures were made in very steady nights so the FWHM value of the combined image is ~0.9″. Complementing the wideband images we acquired also narrowband, H-alpha images to record the effects of the interaction between the galaxies.
The use of this filter set let us to build a very interesting photo, in my opinion. It will comprise six different wave bands. First we have the usual RGB wideband color information:
From the unfiltered image (which contains not only visible light, but also utraviolet and infrared), we can subtract the RGB images in order to isolate the light outside the visible spectrum (mainly infrared light). These isolated sources can be used to enhanced the IR-emitting sources by adding it to the color image. Below we can see these sources as tiny orange-colored dots all around:
Finally, we have two H-alpha lines. The first is at its normal wavelenght of 653 nm, and shows the emission nebulae of one of the galaxies, which is much closer to us than the other ones:
We are going to show this emission as pink:
Finally, to record the Hydrogen alpha emission of the other galaxies (which have a radial velocity of 6,600 km/s) we had to use a narrowband filter centered at 667 nm. This filter shows very well the shock wave between the galaxies:
This emission will show in our palette as red. Summarizing, we have an image with visible-light RGB colors, enhanced IR sources, and two different hydrogen emission lines:
In astrophotography there are many concerns to achieve a good work; time shouldn’t be one of them. In this type of works, it’s not easy to convince yourself if it’s worth the time. Maybe the correct question is “it’s worth the image?” Looking at the results above, for this image I would say definitely “yes!”