Hi Andrew.
Looks to me like diffraction from something protruding into the light column, as others have said. This was discussed in a recent thread that might be worth a read
http://www.iceinspace.com.au/forum/s...d.php?t=133830
The big problem with my 200f4 was that the secondary was not offset so the input light column ended up offset from the OTA centreline. I used to have stars like yours and was only able to improve them by:
1. remaking the secondary to incorporate offset
2. moving the mirror up and using a bigger secondary to get the focuser draw tube out of the way.
There are still some bits and bobs that cause stray diffraction, but it is now a lot more usable.
This might also be worth a try
http://www.iceinspace.com.au/forum/s...ad.php?t=82230
regards Ray