Skywatcher ED 100 focusser adjustment

[mldee (Mike)]

The Crayford-style 2:1 focusser on my SW BD100 refractor seems to be a little under-tensioned, as it doesn't like to move without some push-assistance when the scope is vertical. The tube seems too free and not real smooth. It's got a 1.25 flip mirror with 2" 28mm EP and EOS 1000d attached. I don't think this weight is excessive, but I may be wrong

Has anyone got any useful info on removing the focusser, cleaning and adjusting it? There is only one focus-lock thumbscrew on the bottom, plus half a dozen flush hex-key screws, which are obviously the ones I'm interested in, but would like to hear any prior-knowledge that's around before I start twisting and turning them

[renormalised (Carl)]

Geez, you've got a fair bit of weight attached to that!!!! I'd say you have a problem that is mainly due to that weight being there. The "native" focuser isn't designed to handle all that hanging off it. I'd suggest you get something like a Moonlite or Feathertouch focuser (10:1 Crayford) that can handle that sort of loading and still focus properly.

[mldee (Mike)]

Originally Posted by renormalised

Geez, you've got a fair bit of weight attached to that!!!! I'd say you have a problem that is mainly due to that weight being there. The "native" focuser isn't designed to handle all that hanging off it. I'd suggest you get something like a Moonlite or Feathertouch focuser (10:1 Crayford) that can handle that sort of loading and still focus properly.

That's my next step if I can't get any info here. I have no specs on what the SW focusser can handle, but the little flip mirror is just an el cheapo Ebay special, and the 1000d body is quite light. I'll try it again tonight with a smaller EP, which BTW, are also 1.25, not 2" (Hard to fit in a 1.25 hole)

I've seen all the horror stories here of mounts and focussers as they come from the factory, so thought it would be good to investigate the SW one before I invest many hundreds $$ in a replacement.

[DJ N]

Hi Mike,

I have the Black Diamond ED120, which has the same focuser. When I first recieved it, the action was a bit too loose, and I had a bit of slippage in near vertical position. Basically I checked all the grub screws on the underside, to ensure they were not loose. Then with my camera in place (which is the heaviest item I have that hangs off the ED120, and it weighs close to 800 grams), I slowly tightened the central grub screw until the focuser performed to my "expectation". I do check it now and then, but it seems to perform pretty well.

Hope this helps.

Cheers,

Daniel

[mldee (Mike)]

Thanks Daniel, I'll try your suggestion. Info appreciated.

It's just the right size scope to take nice moon shots with the 1000d, especially using EOS Liveview 5X zoom while focussing. A steady focusser will be the icing on the cake.

[DJ N]

Originally Posted by mldee

Thanks Daniel, I'll try your suggestion. Info appreciated.

It's just the right size scope to take nice moon shots with the 1000d, especially using EOS Liveview 5X zoom while focussing. A steady focusser will be the icing on the cake.

Definitely worth a try!! I have owned my scope since January, and apart from the first adjustment, I have only had to readjust the tension once. Have had no problems with 20 and 30 min subs from dark skies.

Cheers

[mldee (Mike)]

Just went out and tried the grub screws with the scope still parked. Initially I could easily pull the drawtube out by hand.

All the outer (smaller size) grub screws were tight. I then checked the two central larger ones, and found the rearward one made little difference as I tightened it. The forward one made a LARGE difference, but in reverse. The tighter I made it, the looser the drawtube. So, I loosened it off, while 'pulling' on the drawtube and found a nice point where the grubscrew was not slack, and the drawtube resisted my pulling attempts, while still moving smoothly with the focus knobs. I also noticed that the flat on the bottom of the drawtube is not real clean, so eventually might open up the focuser just to check what's inside

I've left it there and will try again later with the scope vertical. It looks promising.