Focus issue??

[julian489289]

Hi

Went out the other night to have a practice with my imaging routine prior to the dark skies returning.  Had a go at M57 Ring Nebula and took 5 x 5 minutes guided & dithered subs with APT at ISO 800 with my Canon 650D through my ES 102m APO.  Processed in DSS and stacked with afew darks and flats.  To me, the stars seem well focused and there does not appear to be any tracking or guiding issues, yet the nebula just lacks focus and clarity. 

Could anyone throw any light on why this might be?? 

Thanks

[michael.h.f.wilkinson]

The nebula by its nature does not have very sharp boundaries. Other than that, I would say the nebula is a bit over exposed, which can account for some blur (or more properly, glare)

[julian489289]

Thanks.  Took 5 minute subs, so what would you suggest duration wise for such a target?

[julian489289]

Have ran the stacked result thru' CS6 and reduced exposure etc, looks much better.

thanks