Originally posted by OSRags Shutter I am limited to no more than 30 seconds.
When you say limited to 30 seconds do you mean you can't set astrotracer to take a shot longer than 30 seconds or that you get garbage results beyond 30 seconds. If it is the first it sounds like something is wrong with your setup if it is the later then it seems normal. I regularly shoot with astrotracer and a 400mm lens but am limited to about 20 seconds before I start getting bad results (unacceptable to me) and I will run a 300mm lens at 30 seconds. Here is
a single shot I captured with my 400mm and astro tracer at 20 seconds. This was a throwaway shot as it was the first one I took right after getting everything setup to check calibration and find out where the lens was at cooling down. This lens takes a long time to come into thermal equilibrium and until it does it shows really bad coma which it is doing here and this was also shot wide open instead of stopped down 2/3 of a stop.
At 500mm I think I would be hard pressed to get even a 20 seconds shot I would consider a keeper.
Originally posted by SteveinSLC Basically if you're trying to do a lot of imaging using a lens longer than 250 or so, you're probably better off getting a tracking mount.
In the long run if one gets serious about astro imaging yes, but for someone just getting started or as a stepping stone it works well enough with longer glass. Although I would say that the 500-600mm range is probably the upper limit of what one could reasonably expect any decent results.
As far as setting expectations of what one can accomplish with longer glass
here is a processed stack I that was captured with my 400mm, K-3, and O-GPS1 with astrotracer. At present I do want to move up to an equatorial mount but it will have to be a bigger one and not one of those little ones as the lens I use alone would exceed their maximum capacity and to ensure smooth operation really need one with a capacity of 30+ LBS.