Rusty,
As Marc says, the images you've presented look pretty good for these sorts of scopes.
But if you are having doubts, there are two things that we as end user can tweak with mass produced SCTs. One of which though is a decision of conscience you need to make for yourself if you want to do it!
1, If your scope shows mirror shift when you focus (and the majority of SCT's do), AND you are only using the scope's native focus knob, you need to adjust your focus AND your collimation in one particular way ONLY or you will never be happy with the image.
Mirror shift comes out of what really is a poor focus mechanism design. It is possible to achieve a mechanism that achieves focus by moving the primary mirror that has zero mirror shift (and the Russian made Maksutovs have been using this for more than 20 years), but for whatever reason Meade, Celestron, Synta and even Vixen have refused to change or have done so stubbornly.
But it is possible to work with mirror shift, but you need to stick to this proceedure.
When focusing, you need to turn the focus knob counterclockwise a little past the focus and then slowly turn the knob clockwise to achieve focus. If you go past focus you need to again turn the knob counterclockwise past focus and then clockwise again to achieve focus. What this does is always sets the primary mirror into the same position and hence puts the object into the same position in the field of view.
When it comes to collimation, with an SCT (or other scope) that shows mirror shift, you can ONLY set the collimation in one position, either inside of outside of focus. You cannot achieve collimation in both positions because mirror shift will never allow the primary mirror to be in the same position both inside and outside of focus. Instead you need to tweak the collimation following the very same routine as I outlined above for focusing. It is only this way that you will be putting the primary mirror into exactly the same position each and every time for focus and hence collimation.
Collimation tip 1: the instructions that come with our scopes always shows a large "doughnut" of the defocused star. This is fine only for course collimation. Final adjustment of collimation needs to be done using a very small doughnut as any error that may be present won't be spread out and hence evened out when the doughnut is large. This goes for all scopes with a central obstruction.
Collimation tip 2: Don't do the collimation procedure with the scope horizontal. Carry out the collimation procedure with the scope at roughly 45 to 60 deg elevation. This is roughly a good average position that the scope would be at as the elevation the scope is at also affects the primary mirror's position!
2, I have come to find that the corrector plate of SCT's and Maks are EXTREMELY sensitive to the amount of pressure that is exerted by the retention ring that holds it in place! MANY times with mass scopes, the screws that hold the retention ring in place are wound in much too tight!!! It really is surprising just how little torque is needed to put on a screw for this pressure to distort the finely ground corrector plate. Remember we are talking about wavelengths of light, not millimeters. This includes the thick corrector plate of maksutovs, not just the thin corrector of SCTs. And if the corrector is being subjected to the strain induced by over-tightened screws the final image will never be as sharp as it could, and can also influence the shape of the doughnut.
HERE is the decision of conscience you face - it is entirely up to you if you will loosen all the screws that hold the corrector's retention ring or not.
You do not need to remove the corrector! Just loosen the screws that hold the retention ring and then secure them in place again. A small lift of the corrector may also free it if it has been stuck in place over the years and dew seeped in under the retention ring. Freeing up the corrector will also release any remaining strain that the corrector may be experiencing.
The last SCT I bought I got it brand new. I struggled for over two years to get the bloody thing to behave and it just would not give me a good image even though I was carefully doing the focus routine for focus and collimation. Out of desperation one day I decided to pull the corrector out to check the secondary mirror. To my dismay I found ALL 6 screws that held the rention ring were all wound in very tight. Worse was to come when I lifted the retention ring and found that the ring was hiding two BIG chips that surrounded one of these screws! The bloody dope who assembled this scope had not only wound the screws too tight but heard the corrector ping when the chips happened, undid the screws, removed the chips and replaced the ring thanking their lucky stars that the chips were hidden by the retention ring! AND they again over tightened those screws.
When I re-secured the retention ring, I wound the screws in to just finger tight firm, not wrist wrenching firm. And guess what? The image the scope through up improved out of sight!!!
I also experienced similar with my Russian made Maks, not from factory assembly but ME! I cleaned the corrector and over-tightened the retention clips!
Not wrist wrenching tight, but still too tight! And the corrector of a 10" Mak is considerably thicker than the corrector of an SCT!
Alex.