Lulin

I had a little success with Comet Lulin over the last couple of nights. The pic shown was on Sat28th/Sun 1st and is a stack of 5x90sec exposures at 300mm f4.
I know that DSS can stack comet pictures but I must be doing something wrong. This was done in Registax 4 (I see that v5 beta is available).
Last night 1/2 March was a wonderfully clear night but I was plagued with hardware problems. My Canon TC-80N3 intelligent release was sticking. At times I was shooting off rapid fire 1/1000sec exposures and later I had no control at all. I fear it may be terminal!