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Skywatcher stock 2" Diagonal slack fit.


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I've happily been using the 2" dielectric  diagonal that came with the ED100 but have noticed it easily loosens. Its not a big problem, nothing has fallen off, but it has  become an irritation.  There seems to be a "wide tolerance" between the diagonal and the focuser and I wasn't sure which  was to blame. It  occurred to me (eventually!) to swap the 2" diagonal from my 80mm refractor to the ED100. Its not a dielectric but its not at all bad and looks well made. Problem solved, nice and fast. I put the Skywatcher in the TS80  and got the  "sloppy fit". Has anyone else had this issue with the stock diagonal and if so any suggested fix?

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43 minutes ago, Alan White said:

Ian, before you do I have bought one of these, it's no better with the stock ed100 diagonal.

Thanks Alan, so it does looks as if the barrel of the stock diagonal is just a smidge under size. This is probably going to sound a bit daft, but when I put a 2" focuser on my TS 80mm  f7.5 refractor, the focuser had more slop in it than I was happy with. My first "fix" was to put 3 pieces of thin adhesive aluminium tape length wise on the focuser tube. Once very lightly greased the focuser had zero slop, was quite smooth but just  tad heavy but quite usable. Thinking of what I could use that was thinner than the tape I decided to strip it back and give it an extra layer of paint. Put back together and re-greased -  perfect! Just the thickness of a coat of paint made all the difference. I am slightly tempted to try the same treatment, although I accept the recommendation that an adapter with a compression ring is inevitably going to be a step up from the current arrangement.

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An interesting and slightly embarrassing update on this. On examining the diagonal I discovered that the barrel was very slightly loose against the mirror housing with a noticeable gap of maybe a tad less than a mm. There was some lateral movement too. In ignorance, assuming the barrel was threaded and it had merely become unscrewed, I attempted to screw it in to tighten it up. This achieved the opposite by loosening it a little more and it was clear that it was neither threaded into the housing and nor was it going to fall out. Wondering how it was held in the mirror housing, I considered that it possibly screwed into a retaining ring inside the housing which was now moving round freely as I moved the barrel. Removing the side of the housing I found that this was not the case and that from what I could see the barrel was held in the housing by just an interference fit.  Also discovered the mirror looked quite dusty!  What to do?  Using a very small jewellers screw driver I very very carefully inserted some liquid metal type Araldite into the 1mm gap all round and pushed the barrel and housing together. Taking off the small amount of excess I could see no adverse effects.  24 hours on the diagonal, reassemble, seems fine with no sign of movement in the focuser.  I am left somewhat puzzled as to how barrel and housing had come apart, even slightly. I am also a little disturbed that the barrel and mirror housing are not held together in a more mechanically sound manner. This is surprising as  removing the triangular side of the housing reveals a very robust looking cast aluminium chassis. Placing potentially large heavy expensive eyepieces in a diagonal that just might fall apart is a niggle at the back of the mind.

Interestingly a 2"  enhanced, but not dielectric, that I bought off a fellow member (F15 Dave?) is heavier and feels more robust and to my eye seems a good bit of kit so for the time being that is staying in the ED100. I shall still be getting a compression ring style adapter as the fitting looks more secure.

 

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On 01/06/2017 at 19:08, DRT said:

You could try one of these, Ian...

https://www.firstlightoptics.com/adapters/flo-compression-ring-adapter-synta-skywatcher.html

Very easy to fit and gives a much better grip than the single grub screw on the standard adapter. Or, if you are feeling flush, you could go for the Baader ClickLock equivalent :wink:

 

Now that is marvellous. Ordered, as I've been having a similar issue.

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Binning it certainly crossed my mind. At the moment it is attached to the 80mm focuser with scope all mounted up in my basement/workshop. I'm thinking about mocking up some weight to hang off the back of it and leave it for a few days and wait for the clunk!

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