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Calling time on Crayfords.


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Sometimes an industry hits a blind spot and convinces itself that a certain design is OK when it isn't. I think scope makers are in this rut with Crayford focusers. Look on SGL. Right now there are at least two current threads discussing Crayford adjustment and repair. I own four Crayfords myself and only one of them is any good. The others slip and on one, bought new 9 months ago, the slow motion is stone dead already. The so called 'lock screws' do precisely nothing and don't prevent slippage. I have never, ever, had the slightest trouble with rack and pinions which DO stay where they are put. To image with all but the best Crayford is to be in a constant state of anxiety with regard to holding focus.

I put it to you that the metal on metal Crayford is an abberration and we, the customers, should be saying NO the things and sending them back until the makers get the message that we don't want them.

Olly

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A well made rack and pinion is excellent - the one on my Vixen ED102SS is really smooth and will also hold the heaviest diagonal / eyepiece combination. Even the old Skywatcher R&P's could be made to work pretty well with a bit of TLC.

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I'm finding the helical non rotating focuser is the way to go...no slip, no movement smooth as silk.

As the only "real" one we could find was the $$$$$$ BORG, we designed and built our own!

It has T thread connections/ 1.25" fittings and gives a positive controlled movement over 20mm. (If you need more - add a spacer!)

The prototype is now in use in Italy and working 100%.

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IMO:

a) Weight load without slippage.

:rolleyes: Electronic temperature adjusting.

c) the ability to 100% automate focusing of the scope without the need to plugin to any other application.

d) Connected via Network so the device has an IP address, not usb or serial.

optional upgrade would be a filterwheel again controlled with the control built into the focuser.

Any colour you want as long as its black.

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IMO:

a) Weight load without slippage.

;) Electronic temperature adjusting.

c) the ability to 100% automate focusing of the scope without the need to plugin to any other application.

d) Connected via Network so the device has an IP address, not usb or serial.

optional upgrade would be a filterwheel again controlled with the control built into the focuser.

Any colour you want as long as its black.

Jeeez, why don't you just pay someone else to do your astronomy for you? :rolleyes:

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Jeeez, why don't you just pay someone else to do your astronomy for you? :rolleyes:

I like to play on my 360 while imaging ;)

My current obsy I still have to open the roof and take of the caps etc.

When i do my next (when we buy our long term home) ill be 100% automated.

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Yep sick of them, my ED80 crayford starting to slip after only 2 months of being out of the box. Stripped it down and rebuilt it and it worked a lot better after that.

The grease they use looks like sludge. reminds me of that scum at the bottom of an old chip pan.... Far from lithium grease!

Currently feeling sick as a dog as I have written off my new Moonlite crayford focuser after a miss hap with good old gravity. Note to self dont walk into the telescope in the dark....

Thankfully (can I really say that...) only the crayford and the RDF were damaged. the OTA, diagonal and TV eyepiece escaped without as much as a scratch.

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Currently feeling sick as a dog as I have written off my new Moonlite crayford focuser after a miss hap with good old gravity. Note to self dont walk into the telescope in the dark....

Thankfully (can I really say that...) only the crayford and the RDF were damaged. the OTA escaped without as much as a scratch.

What a sickener. :rolleyes:

Bad luck fella

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What a sickener. :rolleyes:

Bad luck fella

Yep tell me about it.

Its back in its box until the heart rate has dropped and I can muster up the motivation to see about a quote for the repair.

Damage is two cracked bearings and a bent drive shaft on the focus unit in addition to a dint in the 10:1 reduction knob. I found a couple of split washers which had pinged out as well from between the knobs acting as spacers.

The draw tube seems to have a couple of scratches but nothing too bad. It was not extended at the time so its just marks from the bearings.

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Olly – I think its bad engineering that you are sick off? I have had three high quality Crayfords (Van Slyke Engineering and JIM Telescopes) and all have worked perfectly – no slippage, no backlash I could detect and a positive lock. I also have a very good rack and pinion on my Tak.

I have also had very poor rack and pinion and helical focuser where the engineering was poor with all the problems you list.

What I would ask for is a positive interface between the focuser and the CCD, eye piece etc. No under cuts or compression rings – even the JIM focuser has this problem.

Andrew

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Olly – I think its bad engineering that you are sick off? I have had three high quality Crayfords (Van Slyke Engineering and JIM Telescopes) and all have worked perfectly – no slippage, no backlash I could detect and a positive lock. I also have a very good rack and pinion on my Tak.

I have also had very poor rack and pinion and helical focuser where the engineering was poor with all the problems you list.

What I would ask for is a positive interface between the focuser and the CCD, eye piece etc. No under cuts or compression rings – even the JIM focuser has this problem.

Andrew

I agree with you there mate.

I don't think though that people should have to fork out more money after purchasing a scope to replace a focuser that isn't up to the job.

I understand that most scopes are not made off the shelf for astrophotography work and an upgraded focuser maybe needed but if something has a "focus lock" it should work without shifting the image or pushing the scope out of focus.

Added to that the fact that it's damn near impossible to collimate a skywatcher newt accurately, due to the collimator not sitting in the focus tube accurately time after time. Only a little niggle I know but one that really grinds my gears!

Anyway I suppose with this been a "hobby" it's meant to cost a fortune :rolleyes:

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There are good Crayfords, but just not many good cheap ones. I used to think the Revelation and SkyWatchers ones were OK, but some of the ones I've seen coming through lately have been very disappointing. I suppose you might call the QC variable.

However the Baader Steeltracks are very, very nice with no slippage problems, Well worth the extra over the Revelation / SkyWatcher crayfords. The GSO linear focusers handle loads well, but the refractor version only has 50mm drawtube travel, which is an unfortunate limitation that will require an eyepiece extender in many cases. The Feather Touch crayfords don't slip and work extremely well indeed. Of course they're not exactly cheap.

The Feather Touch R&Ps are indeed about as close to perfection in a focuser as you'll see. They're brought out a new 2" R&P newt focuser that looks very interesting. Love to see a refractor version. Would like to see what the new William Optics R&P focusers are like. Also GSO has a R&P refractor focuser, but not sure when they'll be selling it on it's own.

It looks as if the R&P focusers will become the standard in the mid to higher priced scopes soon.

John

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Olly – I think its bad engineering that you are sick off? I have had three high quality Crayfords (Van Slyke Engineering and JIM Telescopes) and all have worked perfectly – no slippage, no backlash I could detect and a positive lock. I also have a very good rack and pinion on my Tak.

I have also had very poor rack and pinion and helical focuser where the engineering was poor with all the problems you list.

What I would ask for is a positive interface between the focuser and the CCD, eye piece etc. No under cuts or compression rings – even the JIM focuser has this problem.

Andrew

Right with you on compression rings and undercuts. Bad idea at the best of times and a trebly bad idea when they are all in different places. Marks on the EP barrels? For me an EP is for looking through, not at.

But in engineering a bad idea is a bad idea and a steel roller driving a smooth metal surface just is a bad idea. If made well enough this bad idea can be made to work, but why not start off with a good idea in the first place?

If saving money a rack and pinion would be better and that's what we'd soon get if we didn't accept all these naff Crayfords that come as standard on the assumption that we will happily upgrade them in time.

Olly

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But in engineering a bad idea is a bad idea and a steel roller driving a smooth metal surface just is a bad idea. If made well enough this bad idea can be made to work, but why not start off with a good idea in the first place?

I'm inclined to agree. There are probably places where it makes sense (high stress/temperature environments, perhaps?), but a telescope focuser doesn't seem to be a prime candidate to me.

Hydraulic focuser, anyone? :rolleyes:

James

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What happened to the day when all scopes came with a R&P focuser?

For some reason they started supplying them with Crayfords and advertised it as if it was a benefit.:o

I don't even do imaging but they drive me up the wall. ;)

When I used to drive wagons, one of the golden rules was you never put metal on metal, because it slides. If a truck driver knows this you'd think an engineer should be able to work it out.:rolleyes:

Every time I change an eyepiece the damn thing seems to slip and mess about.

Regards Steve

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I think I have been lucky in that all the Crayfords I've used have managed to old my imaging kit without slipping. My Moonlight motorised unit has to cope with a pretty weighty QSI 532 plus SX AO. My humble bog standard agricultural SW single speed orignal crayford carries the QSI in off axis guiding mode very securely.

My gripe is saggy drawer tubes. This is what you need Olly - Bellerophon Focuser - my dream bit of luxury (and totally unjustifiable which is why I want one) bit of kit.

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But in engineering a bad idea is a bad idea and a steel roller driving a smooth metal surface just is a bad idea. If made well enough this bad idea can be made to work, but why not start off with a good idea in the first place?

Isn't that how high-end friction drives work on mounts though??

With regard to the Crayford design, I guess that everything is achievable given enough time and most importantly budget. The issue is, how many of us would like to be limited to having only expensive kit to choose from? For example, the Skywatcher Quattro is less than £1000. If the same scope cost, for example, £1800 with a super-duper focuser, and more importantly that was the only choice that you have, then how would that benefit us?

Being fairly new to this gig, and absolutley not having buckets of cash, what are the high end alternatives? What sort of money does £1K buy? What about £2k? And how many of us would be in the market for such a beastie?

Personally, I am glad that I have a wealth of choice. it means that more people can access the hobby, and that there is a thriving 2nd hand market as people upgrade. It also means that there are opportunities for one-man-band operations to make niche upgrades (for instance I am waiting on a Crawford Machine Crayford to arrive from the States. £118 delivered :rolleyes:).

I guess it's back to the old adage "you pays your money, you takes your choice".

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But in engineering a bad idea is a bad idea and a steel roller driving a smooth metal surface just is a bad idea. If made well enough this bad idea can be made to work, but why not start off with a good idea in the first place?

Olly

Olly - Well I am not so sure it is such a bad idea from an engineering point of view. It has been used to run the railways (wheels & track) and for direct drive telescope drives. However, it does require enough force to provide the rolling friction and this is not a good idea in a poorly designed unit. Its real advantage should be it is simple to engineer with no difficult machining or gear cutting.

We will just have to differ on this.

Andrew

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I have a Tak Sky 90 with a good R & P focuser but it doesn't have a reduction gearing on it so fine focusing on its short FL is tricky. I also have a 16" SCT to which I fitted a Skywatcher Crayford, a big improvement over the standard focus knob. The SW Crayford was "OK" and held heavy components but did not have a fine gearing. I replaced this with a beautifully made SmartAstronomy Crayford which turned out to be very feeble if not adjusted tightly and "gritty" if it was. Just before binning it I decided to strip it down and found the adjstment for the 3 balls that give the focusing action and the 10:1 reduction. By carefully re-adjusting this component I now have a silky smooth focuser with good reduction and plenty of load capacity. From this experience I conclude that some of the problem units are suffering from lack of suitable adjustment.

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Olly - Well I am not so sure it is such a bad idea from an engineering point of view. It has been used to run the railways (wheels & track) and for direct drive telescope drives. However, it does require enough force to provide the rolling friction and this is not a good idea in a poorly designed unit. Its real advantage should be it is simple to engineer with no difficult machining or gear cutting.

We will just have to differ on this.

Andrew

]

But do we differ? I suppose my question would be, 'If this is the right engineering solution at the price, why don't they work?' That they don't work, in the real world of scopes available, is not at issue. They don't. There are dozens of exasperated owners, dozens of threads and dozens of aftermarket upgrades available. Think of all the parts of budget telescopes that never get a mention becuase they do work. Yes, there are budget Crayfords that work but in mass production that's not the point. In mass production you need to ask, Do all of them work nearly all of the time? And with budget Crayfords the answer cannot possibly be Yes. Budget Crayfords are not remotely reliable.

In reflector systems with the focuser at right angles to the incident light then the focuser doesn't have much work to do. Those are not the problem ones.

Olly

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I am not fussed about the type of focuser I have as long as it works well. That said, I have become used to the lovely smooth fine focusing of the DS Crayfords on my scopes and I think this is a major reason why people like them. to be fair I am visual only and my newt focusers as they are on an altaz arrangement, don't have all the weight pushing in or out as the focuser is just above the horizontal.

I suspect that if (and I don't know if it's even feasible at a reasonable price point) R&P focusers had a reduction of 10:1 or similar then people would buy them for sure.

mine have always been OK other than on a frac I bought used with a few months old focuser (I presumed it was older) which had a lot of roughness and after stripping it down and it being no better, I gave up, removed the reduction knob and it's now as smooth as silk and holds a 2" diagonal and 26mm Nagler.

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I got one on one of my WO scopes that slips,A blumming pain.................kev

The crayford on my ZS66 was slipping and I was able to tighten it with an allen key. The Locking knob has an allen socket at it's centre. (details should be in the instruction booklet that comes with the scope)

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The crayford on my ZS66 was slipping and I was able to tighten it with an allen key. The Locking knob has an allen socket at it's centre. (details should be in the instruction booklet that comes with the scope)

I had the same issue on my 150P and resolution, except I had no instructions and was put right on this forum. I put it down to another item on the scope maintenance list.

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A well made rack and pinion is excellent - the one on my Vixen ED102SS is really smooth and will also hold the heaviest diagonal / eyepiece combination. Even the old Skywatcher R&P's could be made to work pretty well with a bit of TLC.

im with John on this, the rack and pinion on my TAL is rock steady and silky smooth

(before anybody says "its only 1.25" no, it isnt, the newer TALs 2009 onwards for sure, have a 2"-1.25" R&P)

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