SCT collimation using artificial star

[Priesters]

Hi,

Yesterday I collimated my SCT using a ZWO camera, SharpCap reticule to get the artificial star dead centre and 'Al's collimation tool' to make the adjustments and everything looked spot on.  Unfortunately I then defocussed in the other direction and collimation looked out.  Not massively but enough to be annoying!  Is this likely to be mirror flop I'm experiencing or something else?  I did have a reducer in the optical path so could that be a factor?

Any help would be much appreciated.

Thanks

 

[michael8554]

I'd say yes.

Only solution is to leave the primary focus with an Anticlock final move and then Collimate, and then only use a zero shift focuser for all other focus changes.

Michael

[Priesters]

Great, thanks for the advice.