Improving Skywatcher ED80 Focuser

[gnomus]

I've had my ED80 for a short time.  People had warned me that, whilst it was a great telescope, the focuser left a lot to be desired.  Sure enough, first time out with it I experienced slippage when my (not very heavy) DSLR camera was attached.

I had seen this 'astronomy shed' video - https://www.youtube.com/watch?v=ofOSAMlqZWw  I wondered if I should have a go.

I purchased a wetstone from amazon - this one - http://www.amazon.co.uk/Grade-Double-Sided-Whetstone-1000/dp/B0099N3CYA/ref=sr_1_1?s=kitchen&ie=UTF8&qid=1424764752&sr=1-1&keywords=Top+Grade+Double+Sided+Whetstone+1000+%2F+3000+Grit  You soak the stone in water for a few minutes before using it, and it will require some additional water placed on the surface from time to time.  

In the video, the chap holds the focus tube in a vice and then works the stone over the top of the tube.  The Amazon stone, however, comes with a rubber holder that keeps the stone on a kitchen work surface.  Therefore, I placed the stone on my worktop and moved the focus tube back and forth over the top of it.  It was very easy to do and it was obvious when the tube was placed correctly on top of the wetstone.  Within a few strokes, it was immediately apparent that I had the same issue as shown in the video - namely that the 'flat' part of the tube is dished, such that the focussing rod was only riding on the edges.  

As I worked the tube, I could see that the plate was becoming flatter.  I did the main work with the coarser side of the stone, and when satisfied I had it 'good enough', I switched over to the smoother side of the stone for a final 'polish'.   It being a wetstone, there was no oil to clean up.  I wiped everything down and set the tube aside to dry for an hour or so before reassembly.  

All in all the 'grinding' part took around half an hour.  I could maybe have got it flatter and I could possibly have spent more time on polishing.  Whether this would have made any difference is questionable.  The main thing is that it seems to have worked.   I have had two sessions so far since the grinding and I have had no slippage.

It was a quick and relatively cheap 'fix', and I thought others might be interested.  No particular 'skills' are required - I would certainly not claim to be especially 'handy'.  

[kalasinman]

+1 ! Sounds pretty handy to me. Good one!

[jambouk]

Good post; i'll look at mine later. Thanks

James

[YKSE]

I guess you've tried this less laborsome way of tuning the focuser?

http://stargazerslounge.com/topic/127051-adjusting-sw-ed80-dual-speed-focuser/

My focusers in my 80ED and 120ED are the same, no problem in holding a kilo (binoviewer).

[gnomus]

I guess you've tried this less laborsome way of tuning the focuser?

http://stargazerslounge.com/topic/127051-adjusting-sw-ed80-dual-speed-focuser/

My focusers in my 80ED and 120ED are the same, no problem in holding a kilo (binoviewer).

I did both jobs at the same time.  I had the Celestron Luminos 31 mm eyepiece in it at the weekend.  It is a beast of a thing.  I had no issues.