Star Test Question

Good day:

I have recently finished a homemade 12.5" F6 dob and recieved the optics. After star testing for several nights, I have observed a consistent pattern on the star test. Outside of focus (6 rings)I have lovely concentric circles with a fat outer ring and evenly spaced/illuminated rings to the central obstruction. This appears to be quite favorable to the pictures and reading I have done on star testing. Inside of focus (also 6 rings) I get a somewhat "fuzzy" version of the same thing. It appears very similar however its not as clear and appear to be shimmering somewhat.
Before I go further, I collimated the scope at 300x (thats about the highest the atmosphere will allow here). The scope was 3 hours cooled, and I was using a 6mm (Nag zoom) focal length eyepiece. Also, used a 2nd mag star.
Can someone please interpret what I am seeing. The in focus views are nice however I may be overwhelmed due to the "new scope factor" and am wondering if the mirror is suffering from a TDE (my first interpretation of the star test) or some other aberration.
I'd really appreciate some input.

Thanks in Advance - Rob

That could also indicate overcorrection. But remember that this test is extremely sensitive to any anomaly, and you may have a fine mirror. TDE also displays a fan of rays around bright objects in focus (kind of like you drew the Sun when in elementary school), more than the expected spikes from diagonal support. A ronchi grating inside of focus will show straight lines (3 or 4) with perfect optics when star testing a complete telescope, they will bow inwards with overcorrection, and have a hook with TDE. They bow outwards with undercorrection. Also give your mirror an indoors scutiny similar to a foucault test, except your eye becomes the source/knifedge. Merely place your eye ~twice the focal length from the telescope mirror looking down the tube (which has been tiped near horizontal). Use a broom handle or chairback (something) to steady your head/eye. Manuvering your view you will notice the mirror blacks out and displays a fine shadowgram. Use more than one procedure to assess your mirror's quality. Ron

Rob, if you suspect TDE, try to test with a 90% aperture, or so, mask. If the pattern remains unchanged (it is going to reduce spherical aberration by ~25%) at least you know what it isn't.