[allan gould]

Last night I went out and started up my equipment to image M83 since it seems to be the flavour of the month. I didnt have too much time as rain was predicted for last night and I was lucky to get 90 min in 15 min subs before it all clouded over.
I was imaging a f10 with my 10"SCT at 2500mm and I thought that I should share some experiences of how I manage to do this when some others find difficulty. I use a 72mm WO DDG scope that sits atop either of my 10" scopes on a Losmandy rail. It is securely bolted to this rail to eliminate any flex in this area. I tried side by side which is a disaster as no matter how well it was made there were too many points where flex could creep in.
The next thing I did was to eliminate the long length associated with the guide camera that is necessary to achieve focus. Originally I started out with extension tubes but they always flexed until I placed a bolt through the Losmandy rail underneath the camera, screwed it up until it supported the weight of the camera which stopped the long length of focuser, tubes plus camera from flexing. Even screwed in extension tubes still flexed until I tied it down to the Losmandy rail using this bolt arrangement. This was a bit of a pain so I eventually hit on my present arrangement where I put a 2" diagonal in place of extending the focuser and an extension tube before the camera. And to adda little cream to the system introduced an x/y shifter just before the camera, a DSI II Pro. This gives a flex free guidescope that I can guide at 2500mm for up to 40 min (done just to see if I could do it). See attached photo guiding.
Ive also attached the shot of 90 min on M83 and also a screen grab of the guiding on M65 through PhDguiding. I should state that that I used PemPro2 to get a very, very good polar alignment on my mount and pier. That also is very important.
Hope this helps someone else.
Allan