southup

1 minute ago, southup said:

Hey Robin David,

The other day I recollimated the Focuser with the Takahashi collimator being threaded from 117mm to 36mm (takahashi thread).Much better results Than The cliplock ,howiclatta combination. By the look of you image your focuser is out.This has to be on axis before anything else is done.I'm still seeking the perfect image out my 16"rc.

Focus should be around 310.9 mm from the backing plate of the cell on a gso  rc16a.You may need to recheck your focal lenght.
hopfully not to painful

Best david

Move your primary before touching the secondary.1/4 to a 1/3 of a turn in on the collimation bolts should do it.

On 22/02/2017 at 07:54, Robindavid said:

Hi All,

I think my problem is solved. As Andrew suggested I checked the focal length and it was 3275 instead of 3250. I could increase the distance between the mirrors by screwing the supporting screw of the secondary. I estimate that I moved the secondary some 5 mm. The results was a decrease of the focal length. After that the collimation took 15 minutes following the DSI method. The stars are now round in the center even when little defocused.

Thank you everybody.

 

Hey Robin David,

The other day I recollimated the Focuser with the Takahashi collimator being threaded from 117mm to 36mm (takahashi thread).Much better results Than The cliplock ,howiclatta combination. By the look of you image your focuser is out.This has to be on axis before anything else is done.I'm still seeking the perfect image out my 16"rc.

Focus should be around 310.9 mm from the backing plate of the cell on a gso  rc16a.You may need to recheck your focal lenght.
hopfully not to painful

Best david