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Help with WP FLT98 Focuser


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I have a William Optics FLT 98 which I have been using sparingly during 7 months. Now the focuser is giving some problems. It will not hold the weight of even heavy eyepieces, much less cameras. When locked, it will hold any amount of weight, but while focusing it will slip almost constantly. I understand there is a way to increase the tension, but I do not know how. I shall appreciate if any member knows how to do it. I am enclosing two photos of the focuser as a reference.post-34394-0-54794200-1422204113.jpgpost-34394-0-54794200-1422204113.jpgpost-34394-0-97474600-1422204122.jpg

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Drive tension on the WO Crayford focuser is adjusted by turning the central grub screw with a 3/32" (imperial size) allen (hex) key, clockwise.

Just add enough clockwise tension to the grub screw to stop the focuser tube sliding, you may damage the flat surface of the focuser if you try to tighten too much.

It is also important to keep the flat-brass running surface of the focuser free of grease or oil, if necessary wipe it clean with isopropyl alcohol or methylated spirits.

I have seen on a few forums that the grub screw on this WO focuser can work loose unnoticed and fall from the telescope, this might be your situation since I can not see the grub screw in your photographs.

If your grub screw is missing then there is nothing special about it, any flat nosed (not pointed) grub screw with the correct imperial thread can be used as a replacement, a car or motorcycle repair shop should have one that will fit, you can even use a plain headed screw as a temporary fix.

Photos below show the grub screw and hex key in place for adjustment.

 

 

 

Edited by Oddsocks
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Glad I found this thread as my Meg 90 had been giving me focusing problems, it would focus out, but wouldn't pull the imaging train in at any reasonable inclination. I hadn't spotted the grub-screw until I saw the photo, now I've tightened it a bit it will focus both ways.

I'd still be wary of buying anything WO, the Star 70 might be an exception.

Edited by DaveS
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Funny, I have 3 WO scopes and all 3 focusers work great. No issues lifting anything I've thrown at it including a 314/filter wheel/flattener setup. Dslr/flattener setup. 2" diagonals with 2" eyepieces. Maybe I just got lucky 3 times.

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  • 2 weeks later...

Thanks Oddsocks. The screw was in its place. Applied just a tad of tension and now it is perfect. Mounted the big SBIG with filter wheel and cables and it held perfectly at the zenith without tightening the locking screw. I am very glad I bought this scope (the FLT98), it gives me pinpoint stars and great views.

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I have to say that my own experience of WO telescope ownership has been very positive indeed, including the use of their focusers for astro-imaging. The only caveat to that is the DDG Crayford focuser on my Megrez 72 which works perfectly with my OSC SXV-M25c but struggles to pull my rather heavy QSI 683 WSG-8 up hill. 

I ordered a Feathertouch R & P to go with my FLT98 on the advice of the supplier but had to wait for it to arrive so for a few weeks I used the standard WO Crayford for imaging with great success.

On the other hand, I sent my Takahashi FSQ 85 back for a refund because it frankly wasn't good enough ..........

Horses for courses :grin:

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I've recently purchased the new latest version WO FLT98 with the 3.5inch R/P focuser, which as the turn click lock collet type holder. I hang a ATIK EFW2 and 460ex on the back of this without any problems whatsoever. in fact  I think I could easily double this weight and it would still not be of any concern, it really is rock solid. Up front you have the superb razor sharp triplet lens designed by G strakov a top Russian designer. This scope really is top Quality and is a keeper for sure.

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