Zenithstar II 80ED

[astrofox]

Has anyone any experiance of adjusting the Crayford focuser tension on this tube. It's started slipping now I am pointing at summer objects near the zenith.

[russ.will]

I had one and I have to say the focuser looks pretty. That's the good bit, otherwise it's pretty ropy, something which seems to afflict WO 2" focusers in general (DDG included) and nobody seems to point out until you have one!

I found the best way to adjust it was to remove the focuser from the main barrel of the scope so you could see inside the focuser. There are some gub screws that adjust the rotation tension near the black mount collar that hold it on. Inside, there are two bearing plates at the top,that the draw tube is tensioned against and these are adjusted by allen grub screws set in the focuser barrel at each end of the plates. Once you can see inside the focuser, It's easier to adjust these so they plates bear evenly along their length on the draw tube. This not only helps with smoothness of travel, but helps avoid some of the alarming sag the WO focuser suffers from. Once this is done, it's also easier to set the correct tension on the focusing wheels. Mine was prone to only fine focusing in one direction when pointing in all directions. Once adjusted it was only really when pointing at zenith, with the 450D and feild flattener attached, that it struggled.

To be honest, I gave up with it in the end, as you could never eliminated the sag and focus shifted too much when using the locking screw. You could nail focus with effort, but I always felt like I was battling the scope, rather than it helping me.

On the plus side, the focuser was okay for visual use and well able to hold the weight WO 2" dielectic diagonal with a 32mm Panaview EP in it.

Russell

[astrofox]

Many thanks Russ

I'll give it a go tomorrow.

Makes you wonder if we are being sold a pup with Crayfords. I have a Messier 127 with R&P that is so smooth and rock solid. Just wish it had a 10:1 reduction.

[John]

.....Makes you wonder if we are being sold a pup with Crayfords. I have a Messier 127 with R&P that is so smooth and rock solid. Just wish it had a 10:1 reduction.....

There was a thread on this a while back in the equipment section. I seem to recall the general conclusion was that a well engineered rack and pinion was preferable to most of the crayfords available, with the possible exception of the Moonlite and Feathertouch brands.

When I started out in the hobby and for many years 95% of all scopes were fitted with a rack and pinion focuser and crayfords were mostly DIY made. There was a big surge in consumer interest in crayfords about a decade ago, the market responded and now your can't move for the things. Many of them look really glossy but often don't have performance to match, unfortunately.

I believe the latest William Optics scopes are now using a rack and pinion design again so maybe thats a step forwards

[nightfisher]

There was a thread on this a while back in the equipment section. I seem to recall the general conclusion was that a well engineered rack and pinion was preferable to most of the crayfords available, with the possible exception of the Moonlite and Feathertouch brands.

When I started out in the hobby and for many years 95% of all scopes were fitted with a rack and pinion focuser and crayfords were mostly DIY made. There was a big surge in consumer interest in crayfords about a decade ago, the market responded and now your can't move for the things. Many of them look really glossy but often don't have performance to match, unfortunately.

I believe the latest William Optics scopes are now using a rack and pinion design again so maybe thats a step forwards

Yes, a lovely design, but not with out its fair share of problems

[russ.will]

I believe the latest William Optics scopes are now using a rack and pinion design again so maybe thats a step forwards

I think that fact alone tells you all you need to know.

Russell

[andrew63]

With the new season approaching - looking forward to what the new colour scheme and focuser william optics come up with! Can now appreciate what parents go through when the new home strip is paraded

[Peter Drew]

You can easily improve the performance of a "weak" Crayford by attaching a couple of rubber bands to the eyepice locking screw and the main OTA, this gives more forward effort.