A320Flyer Posted June 16, 2019 Share Posted June 16, 2019 Hi folks I own a SW150P which I use with a ZWO183MM Pro/Filter Wheel/ Baader MPCC. With the correct 55mm spacing to the CC, I need to rack in the focus tube to get focus. This means I get horrible little “nibbles” taken out of my stars where the focus tube interferes with the light path. I’m thinking of “upgrading”to the 150PDS as I understand that the primary mirror is set nearer the focus tube to avoid this. Can anyone confirm? Will I still get the “nibbles” with this combination? Thanks Bill Link to comment Share on other sites More sharing options...
Ronclarke Posted June 16, 2019 Share Posted June 16, 2019 You won't, you are right with saying the PDS model has the mirror nearer so no 'racking' in needed.. Good luck Ron Link to comment Share on other sites More sharing options...
alacant Posted June 16, 2019 Share Posted June 16, 2019 29 minutes ago, A320Flyer said: nibbles Hi. Same on my 130pds. Easiest way is to saw off 10mm of the inner focuser barrel where it enters the light path. HTH. Link to comment Share on other sites More sharing options...
R26 oldtimer Posted June 24, 2019 Share Posted June 24, 2019 I went with a bresser 150/750 newtonian, after reading about focuser protruding issues in the 130pds. It seems to me that is better built than the pds series with it's massive 2.5" r&p focuser. Used with a DSLR the focuser protrudes about half a centimetre in the telescope tube without entering the light path. I am also under the impression (not sure though), that it comes with a slightly bigger secondary than the 150pds. Overall, I would say it's a very nice alternative to investigate. Link to comment Share on other sites More sharing options...
A320Flyer Posted June 26, 2019 Author Share Posted June 26, 2019 Hi guys. Thanks for all the responses. In the end, I simply removed the collar on my mpcc which allows it to be pushed further down the draw tube. To now get focus I have to rack the draw tube out a bit which has cured the nibbles. Bill Link to comment Share on other sites More sharing options...
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