If anyone is contemplating DS imaging be that with CCD or a DSLR, may I suggest the E180? I made that decision last year and have have never looked back. To shoot at F2.8 and have pinpoint stars right to the edge, beats all comers.
If using a FF DSLR you have a 500/2.8 lens and if using a 1.3 cropped sensor like the 60Da, then it's a tad higher, but hey, with an ISO setting of 800, exp. are so short (3-8mins), you don't have to guide! I do anyway as I've got a GSO 6" F4 in tandem and SW BD 5" g/scope with a Lodestar. While Tak make gear that lasts, don't cut your nose to spite your face. Quality has its price and Tak's are no exception.
Look at those who chose to use RC's. They chose them for larger aperture while working at F8, but that is 5 stops slower than an E180!!
Now if only Tak made an Epsilon 300 F2.8......
As a retired photojournalist, lens speed and ISO is crucial in low light. That is common knowledge and in astronomy, there's no exception. Aperture and fast ratios, allow lower ISO's to be used to get better quality images. In the days of film, we only had 125 and 400 ISO emulsions. Konica had a 3200ISO colour which was good for those who wanted false colours in their stars!
So get that E180 Simon, and make me happy knowing you have one!
