extended exposures with sc c11

You guide on a star and your image has blurry stars? That sounds like polar alignment is off or your guiding is not working.

Hello,

It maybe that you're experiencing mirror shift. As the scope moves, because the mirror is just resting on the central baffle it can shift around as the scope tracks across the sky. Of course this won't be seen by you guide scope. You will need to use either an OAG or an ONAG. I use the latter, but with the Edge HD which also has mirror locks to keep the mirror in place.

Cheers,
Ian

You're running up against stuff that is neither intuitive nor obvious.

Tracking difficulty increases very fast as the focal length increases.  It is not linear, ie twice the focal length is more than
twice the difficulty.

As others have stated the mirror moves.  Most people imaging with a C11 use an off axis guider to combat this.  And an
expensive guide camera, which the OAG wants.

Weight hurts, too.

The bottom line is that imaging with an ED80 is relatively easy.  A great starter scope.  The Newtonian is mildly difficult.
A scope for someone with experience.  The C11 is very hard.  Really, an expert's scope, and one that requires special
equipment.  A focal length reducer is used by most C11 imagers.

Not intuitive, not obvious.  But true.

Best advice.  A couple of years  (not kidding) experience with the other scopes would be good before tackling the C11.  It's better used as a visual scope or a planetary imaging scope.  Not DSOs.

Dont blame me if this does not work for you!! lol
Most of this can be done during the day. The Guiding will have to wait until night!Make a note of all your PHD2 settings. All the info in the brain too. Put that info somewhere safe

I used to have a similar setup. The C11 on a NEQ6 Pro mount with a 80mm guide scope is adequate.
I found I had similar problem to this. Would start guiding and after a few moments, PHD2 would go walkabout.
Now, as I said..//Dont blame me if this does not work for you!! lol

My remedy was -
Before powering on, check the balance of the equipment! One at a time and make sure one is tight before releasing the other. Release the clutches and see if the OTA and the weights balance?
Move the OTA and weight so they are horizontal, close the DEC clutch and release the ALT, does that OTA with all its accessories attached, including DEW shield if used. Balance OK? If so, Great
Power on, Start again with PHD2. Click on the Brain. Select RESET CONFIGURATION. Do the darks for the guide camera. Check all the settings are good. Slew to a star around 30 degrees above the horizon and start guiding. It will do its routine, north, east etc. When it starts guiding Open TOOLS and select Guiding assistant. Run that for at least 2 minutes. Apply the results, slew to your prefered area of sky and try imaging.

Good luck

As I said, this works for me. Maybe there are better ways, I don't know. I am, like many of us, self taught
Use at your own risk