A problem with collimation of 150 PDS

[lensman57]

Hi,

I picked up an SW 150 PDS the other day, to say that I am a bit disappointed is putting it midly. The double speed focuser  was not even tight in its housing and the locking grub screw ( clutch side ) had not even been tightened up so the shaft was loose with no pressure on the draw tube and in fact it was free of its housing. I think that I have sorted these out. Collimation was nowhere near acceptable but this I could accept, it has travelled from China and man handelled in the UK.  The secondary  mirror position was way off, the problem I am having is that no matter what I do to the retaining  screw for the secondary I don't seem to be able to center the Secondary's reflection in the draw tube. I have a good circle equidistant from the edges of the tube but it is not in the center as Shown in Atrobaby's photos. I have finished the collimation using a sight  tube and a cheshire collimator  with the clips visible and the distances are good. My question is wether not being able to center  the secondary in the draw tube matter as no matter what I do it does not seem to shift either way and what can I do with this if need be, I want the scope for imaging btw not observing.

Thanks for your help in advance.

Regards,

A.G

[Peter Drew]

Are there adjusters on the spider vanes? if so, loosening one and tightening the other two would move the secondary physically relative to the focuser. 

[dobbie]

hi a.g , have you taken out the secondary mirror and spinder vanes to see if all the bits are in order, there should be 3 grub screws and a spring on the main screw to allow it to move forward and back .

dion heap of astronomy shed fame as posted some excellent videos on you tube the first and second in the series deal with this in detail ,

hope this helps , dobbie .

[lensman57]

hi a.g , have you taken out the secondary mirror and spinder vanes to see if all the bits are in order, there should be 3 grub screws and a spring on the main screw to allow it to move forward and back .

dion heap of astronomy shed fame as posted some excellent videos on you tube the first and second in the series deal with this in detail ,

hope this helps , dobbie .

Hi Dobbie,

Yes I have done all that, no joy . I may take the whole lot out and start from scratch. I am hoping that it stays clear for little while tonight so that I could do a star test and see what it looks , if it is bad then  I will have to dismantle the whole lot. To be honest one of the reasons I got the 150 was that I thought it may not require rebuilding otherwise I would have gone with my initial choice of the 200 Quattro. Well if all fails I still have the APO standing by even though is wideangle.

Regards,

A.G

[Skyline]

Quality Control is paramount, I do wander is there a difference in quality over a GSO or a Celestron Branded Newtonians, as I have had a few Celestron Newtonians in the past & their QC seems a lot better then Skywatchers, even though Celestron & Skywatcher  fall under the banner of Synta.

Im sure once you've put it together again, it would be like a fine tuned Astrograph

Al.