FSQ85 focuser

[ampleamp]

Typical! The first clear non-moonlit night for ages round here and I get out to the shed to find that I can't achieve focus on the scope. I quickly realised that the focuser was not going in far enough and was actually short by about 1.5 inches.

I brought the scope in and removed the focuser, and the actions seems to be very clean and work well. The problem appears to be some sort of internal blockage that is preventing the whole draw tube to enter the body of the scope.

First pic is the furthest the focuser will go in.

Second pic is the internal of the focuser - seems fine.

Does anyone know if I can unscrew down the black join in the middle of the scope or is this a potential send to someone; and if so, who? Scope is second hand but may well phone Ian King in the am.

Thanks

[Oddsocks]

Cutaway image of FSQ85 attached.

The something you are hitting is probably the rear corrector element.

The rear corrector element projects inside the focuser draw tube by a few centimetres when the focuser is wound all the way in.

The black ring is part of the mounting for the rear corrector element, I don't think opening the tube there will help you see what is happening as you will possibly end up being the wrong side of the corrector.

To get to the back of the focuser draw tube and the front of the corrector the green focuser body has to be separated from the white tube but I don't know if this is just a thread connection or a thread connection with Loctite or a push fit with glue, perhaps Ian will have the answer to that one or possible Olly Penrice if he ever took his FSQ85 apart.

It might just be that something has pushed the focuser draw tube to one side so that it is no longer able to slide over the rear corrector assembly.

Check that the screws for the finder bracket have not been fitted back to the green part of the focuser body, without the finder bracket actually fitted, and screwed in so far that the tube is pushed to one side.

Also check that the focuser draw tube support bearings have not come loose and the focuser tube is no longer parallel to the tube axis.

I remember reading another thread somewhere a year ago with exactly the same problem and I was sure that was due to loose adjuster bearings pushing the draw tube to one side but I have been unable to find it, possibly another forum....

Be interesting to hear what the problem actually is as I am thinking of placing an order for one this spring.

[ampleamp]

Sometimes life smiles on you and sometimes it doesn't and you look a fool. I have worked out the cause of the internal blockage. 

As i was trying to fit the scope into its original box to courier i noticed two scratches along the drawtube body. They matched the bolts the would normally hold the finder in place; and since i had removed it, I had screwed the bolts in to stop them being loose and it is these bolts that caused the stoppage. You can guess what I called myself when i realised my brain-fade.

I now have a couple of washers to mimic the depth of the finder foot, and all is well; no stoppage!.

Thanks to Oddsocks - i will join the band of idiocy but I am glad i have found the problem, even at the expense of some self esteem.

Oddsocks - I can't recommend the FSQ highly enough - all that you will have heard is true - but obviously it is up to you whether you feel it is worth the extra over and above say and Esprit 80 or some other very good scopes in this range; I buy second hand and for me it was worth the extra