Focus tube slipping with weight of DSLR

[Fordos Moon]

Morning all.

The other evening was fairly damp as I set up to image the moon. I did eventually get a pretty good image (attached) but it wasn't without difficulty. I was using my ED80.

I could not tighten the focus adjuster screw tight enough to stop the weight of the camera pulling down the focus tube every time the scope slewed to look upwards. It took about 4 attempts before the tube stayed in focus.

Is there an after-market mechanism, replacement or a quick fix that can hold my focus tube more firmly to combat the weight of the 1100D?

[leelee970]

Nice image Fordos, when did you take this - and was it a mosaic?

[emadmoussa]

As soon as I read the title I thought you were probably using the 80ED.

I don't know anybody who didn't have similar issue. The best thing that kept it solid for me was a SW auto focuser. I fiddled a bit with the hex keys but nothing much happened... However the guy who bought it from me managed to get tighten it up well and he says it's solid now.

[leelee970]

sorry I've no suggestions on focus - having a Newt, I simply rotate tube so camera etc are better balance and not pulling downwards.

[Fordos Moon]

Nice image Fordos, when did you take this - and was it a mosaic?

Thanks Lee. I took it a few days ago. And nope, just best 80 or 90 frames stacked using PIPP and Registax.

[emadmoussa]

From Astronomy Shed:

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Hi all, Out with the ED80 yesterday and found that when I put my DSLR onto the focuser it started slipping.
So after googling and finding no solutions, this is what I did....
(this may void the guarantee on the scope)



A= The 4 bolts that hold the focuser to the body.
B= Side adjustment bolts, they are threaded into the tension plate.
C= Focus locking knob
D=Centre adjustment bolt.
E=Height adjustment to body bolt.

The 4 bolts (A in the photo) hold the focuser onto the body..... I removed them and carefully removed the focuser. There are 4 tiny rubber 'o' rings between the focuser and the body, so watch out they dont fall off, or into the tube.



Now from the angle of the tension plate you can see that its only been running on one side, this plate should be even to provide the most friction to the tube.

The two bolts ( act like a seasaw on the center (D) bolt.



After adjustment you can see the friction plate is now level, keep adjusting it up untill the focuser feels smooth. You have gone to far is it starts to feel jerky and tight.
Word of advise DONT put any grease on this, as it need friction to work.......

Once adjusted, just put it back together with the rubber 'o' rings between the focuser and the body, tighten up the 4 fixing screws and its done.

Took me about 10 mins to do.....I can now hold the scope by the focuser and it doesnt slip, and its still solid with my DSLR and barlow hanging of the back.....

So a job well done......

[Steve Ward]

Also worth fettling the draw tube , the 'flat' bearing surface comes slightly 'hollow ground' from the factory due to the method of machining and the roller bar only comes to bear on the outside edges.

Follow this tutorial that shows both the problem and the cure ... 

http://www.astronomyshed.co.uk/forum/viewtopic.php?f=19&t=579