Telephoto Camera Lens Assists Dark Matter Find
Small telescopes are very useful for searches for extremely faint, diffuse galaxies because it turns out that these searches are surface brightness limited rather than being magnitude limited like most surveys.  Surface brightness is a little counterintuitive because the minimum surface brightness a survey can find is actually independent of telescope size.  Using a 8-m telescope is no better for finding a diffuse galaxy than a telephoto lens.  The only thing that can improve your signal to noise ratio is observing time and observing time is much cheaper on a small telescope.<p>The basic reason for this is that as you increase the size of your telescope, not only does the collecting area increase, but the area of the image increases as well.  So if you&#x27;re looking at a diffuse source like a galaxy, the increased number of photons gets spread out over a larger area and the total number of photons per pixel remains the same.  This isn&#x27;t a problem for point sources (like stars) because even as the image size increases, all the photons from a point source still fall in the same pixel so the source appears brighter to the detector.<p>As peter303 also mentioned, refracting telescopes don&#x27;t suffer from the same artifacts that reflecting telescopes do, which is why these surveys use small telephoto lenses rather than small reflectors.