6 inch f/5 problems

The image: inside focus no defraction rings "just one big one on outer portion of star image " Vega " at 350X. Disk in center. Outside focus near perfect defraction rings at 350X Disk in center. At tight focus 3 images superimposed on one another and no airy disk.
The planets: three disks superimposed on one another. No tight focus obtainable. Image is badly distorted.
Collimation: Laser perfect hit in center.
Cheshire: concentric no visual offsets. As perfect as I can get it.
Star test: At tight focus three tails where viens are but no airy disk "its gone".
Worked for hours to achieve better image but nothing I do fixes it. Only gets close.
Any suggestions ? Don't suggest "throw it away". I really would like to use it.
Maker of scope unknown. Quality unknown. A label stating made in USA but nothing else other than a placard warning of Sun usage. Its brand new. Secondary was turned slightly sideways so had to do something to fix it.

Does this happen with every eyepiece?

RE: Colimation perfect hit in center--that does not necessarily mean you are collimated. Although if the chesire is right, and the dot is in the middle, it means things are right.

Alex

My suggestion: loosen the mirror lock-downs. It sounds like you may have an astigmatism induced by the little flanges that hold down the mirror. I had similar problems to yours in a 16" reflector and cured it doing the above. You SHOULD be able to "just" feel the mirror move around in its cell...

Pat Plunkett

Tube currents sometimes produce "funny" effects. What brand is your scope anyway?

Erlend

I'd have to see the star test "live in color" to be certain but it sounds like your mirror has either a turned-down edge (TDE) or severe spherical abberation (maybe both?). Make a mask with a 5" o.d. hole in it and place that over the front of your scope. Rerun star collimation and star testing after the scope has reached thermal equilibrium. If the star test cleans-up, the problem is TDE. If the star test remains cruddy, it's probably severe spherical abberation. You will likely need to replace the mirror if I'm correct. It's not worth the money to refigure a 6" mirror.

Dave