|
I’ve only used 6”, 8”, 10” and 12” Newts
Looks like a combo of either pinched optics and bad tracking ( polar alignment) or mirror flop. A flare on one side of the Star is typical of pinched optics.
Maybe try a couple of quick tests during a clear stable night
Unguided Star test
Don’t rely on your guiding alone , take a 30 sec to 50 sec unguided exposure on a mag 2 star at 40 deg Alt and then at 70 deg Alt. Zoom in on the exposure and compare Star shape and diffraction spikes. Stars should be round if mount is tracking correctly and PA is below an arc min. Obviously the star shape at 70 degrees will be sharper than at 40 degrees.
Pinched Optics ( Defocus Star test )
Slew to a mag 2 Star and defocus the Star into a large donut. The Star or large donut should be circular and uniform and also be able to see the spider vanes and the 3 mirror clips. If not , check primary mirror for pinching and flop. Use cork strips to eliminate flop and ensure rubber mirror clamps are only just touching mirror.
Check Guiding
If using PHD2 for guiding run the guiding assistant to give you a sanity check on your optics and mount performance.Mount could have severe Dec backlash. Worm gear could be the reason why the optical problem changes in different parts of the sky. Only a hunch ??
Re check Collimation using both Cheshire and Laser as well
Finally there’s a load of photo examples of optical aberrations with Newtonians online , Stargazers Lounge , Cloudy nights and even on some old IIS posts , they may match something similar to yours
Good luck
Martin
Last edited by Startrek; 26-06-2025 at 09:47 PM.
|